Effects of Fasting & Time Restricted Eating on Fat Loss & Health | Huberman Lab Podcast #41

[offbeat uplifting music]

- Welcome to the Huberman Lab Podcast,

where we discuss science

and science-based tools for everyday life.

I'm Andrew Huberman,

and I'm a Professor of Neurobiology and Ophthalmology

at Stanford School of Medicine.

Today, we're talking all about fasting.

And anytime we're talking about fasting,

we are also talking about eating,

because we all need to eat sooner or later.

We're going to talk about how fasting

and when we eat influences

a large range of aspects

of our health and wellbeing, both physical and mental.

So, well, nowadays,

most people are familiar with the term intermittent fasting,

also sometimes called time-restricted feeding.

I think most people don't really understand

how that process works.

It's sort of obvious that intermittent fasting,

aka time-restricted feeding,

involves eating at certain periods of each 24-hour cycle,

or maybe even not eating for entire days, in some cases.

But, if you think about it, everybody sleeps eventually.

And therefore, because people don't eat during their sleep,

almost everybody is employing some form

of intermittent fasting or time-restricted feeding.

What we're going to talk about today

is how particular schedules of time restricted feeding

can impact our health in different ways.

And when I say different ways, I mean,

we're going to talk about how intermittent fasting,

aka time-restricted feeding, impacts weight loss,

fat loss in particular,

muscle maintenance, and loss and gain, organ health,

such as gut health and liver health, the genome,

the epigenome, inflammation, sickness, recovery,

and healing from sickness, exercise, cognition,

mood, and lifespan.

So we're going to cover a tremendous amount of information.

I promise to make it all directly accessible,

regardless of whether or not you have

a background in biology and metabolic science or not.

I'm also going to talk about a lot of tools.

In fact, I'm going to discuss

a number of tools during today's episode

that actually make it such

that you don't have to follow any feeding schedule,

or fasting schedule, same thing

if you think about it,

in any absolutely strict regimented way,

meaning if you were to only eat during an eight hour period

of each day, most of the time,

but then occasionally eat across a 12 hour period

of the day,

in theory, that could actually have pretty serious

detrimental health effects.

And yet, there are things that you can do

to attenuate those negative effects.

In fact,

there are things that you can do and or take

that can make it as if you did not eat at all.

And so we'll discuss what those tools are.

And in many cases, for sake of health, weight loss,

and performance,

making the body think that it did not eat at all can

actually be quite beneficial.

So today, we're going to cover mechanism

and we're going to cover tools.

Before we do that,

I want to highlight a particular result that was published

recently, because it serves as a useful backbone

as we wade into the conversation about fasting.

This is a study that was published

in the journal Cell Metabolism: A Cell Press Journal,

excellent journal.

And the title of the paper is "Fasting Blood Glucose

as a Predictor of Mortality: Lost in Translation".

And I'll explain what the "Lost in Translation"

part means in a moment.

But the basic takeaway of this study,

and I should mention that

the first author of the study is Palliyaguru,

PALLIYAGURU, guru,

Palliyaguru, et al.

The basic finding of the study is that in humans,

higher blood glucose is associated with mortality.

And in fact, if you look at blood glucose,

resting blood glucose across the lifespan,

what you find is as people age,

resting blood glucose goes up.

Now, this is very interesting,

because for a long time it was thought

that metabolism actually goes down as we age.

And to some extent, that's true,

but the reductions in metabolism

are not nearly as robust as we once thought

that they were across the lifespan.

However, unless there's something done

to mitigate the increase in blood glucose associated

with the aging,

almost everybody experiences a gradual,

but regular increase in resting blood glucose

that predicts mortality.

Now, the title, as I mentioned,

is "Fasting Blood Glucose as a Predictor of Mortality:

Lost in Translation".

And the reason that they included "Lost in Translation"

in the title is that what I just told you,

that increases in resting blood

glucose predict mortality, or are correlated with mortality,

is true for human beings

and for non-human primates, monkeys.

But the opposite is true in mice.

And so I thought it was important

to use this study as an example

of where it studies in mice often,

but not always, translate to humans

and to non-human primates.

So today, I'm going to be careful

to distinguish when a study

was performed in mice versus in humans,

because it seems that at least when discussing feeding,

blood glucose and other aspects of diet

as they relate to health and wellbeing,

whether or not a study was performed in rodents

or in humans can be very important.

In this case,

the results were directly 180 degrees opposite

to one another.

In other words, in mice,

resting blood glucose went down,

and was associated with mortality.

So lower blood glucose associated with mortality.

Whereas in humans,

higher resting blood glucose was associated with mortality.

And obviously,

what we're mostly interested in is health

and wellbeing of ourselves, of humans.

I'm sure there are some people out there that are intensely

concerned about the health and wellbeing of mice,

which you could imagine

a few rare contexts where that's important,

but obviously most of us are interested in human health.

So I'll be sure to emphasize when studies were performed

in humans versus in mice.

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Okay, so let's talk about feeding, fasting,

health and performance.

And I want to just establish a few foundational terms

so that we're all on the same page.

First of all,

rather than talk about fasting or time restricted feeding,

I'm largely going to talk about time restricted feeding,

but please understand that time restricted feeding

is just one side of the coin

that is a two-sided coin

that includes fasting on the one hand,

not eating, and time restricted feeding on the other hand,

I may occasionally say fasting,

but because fasting and eating establish different

biological conditions in the body,

time-restricted feeding

is the term that I will use to describe

the overall plan of restricting one's eating window

as it's called to a particular phase of each 24 hour day,

or in some cases two particular days within the week.

Because as you'll soon learn,

there are aspects of time restricted feeding,

aka fasting, that involve eating every other day,

or eating one way for five days

and then fasting for two days, and so forth.

So I'll be very precise about what I mean and why I mean it.

But for the time being,

I'm going to refer to time restricted feeding

as a way to put an umbrella over this conversation.

Second of all,

I am going to emphasize a lot of biological mechanism.

If you've listened to this podcast before,

you know that I always begin with biological mechanism.

I do describe tools of how to implement those mechanisms,

but I wholeheartedly believe that knowing mechanisms

and understanding how these processes work

gives you tremendous

flexibility and understanding,

and control over the processes

of your mental and physical health.

Whereas if I were to just list off a menu

of things to do and not to do, those will work,

but those will not give you the kind

of understanding that would allow you

to navigate through life, through travel,

through dinners out, through different exercise schedules,

whether or not you're one age or another age, male, female,

et cetera, I'm giving you mechanisms

so that you can gain more control over the systems

in your brain and body.

Everything's timestamped,

so if you want to jump to the to do's,

you can certainly do that,

but I encourage you to hang in there for the mechanism bit.

I will make it all very clear

because if you understand mechanism,

you are in a true place of power and control

over your biology.

If ever there was a topic that is controversial,

especially on the internet,

it is that of diet and nutrition.

So I'm wading into this with a smile and in eager

anticipation of all the but but but this

and but but but that, and wait,

but this showed that.

Here's the deal,

we need to precisely define

what it is that we're talking about

when we talk about nutrition.

I'm going to give you an example

of a study that was published a few years ago,

2018, by a colleague of mine at Stanford,

Chris Gardner, he's a terrific professor

of nutrition and has done a lot

of important studies on how nutrition impacts

different aspects of health.

This is a large-scale study.

It was published in JAMA,

the Journal of the American Medical Association,

one of the very top tier journals in the area of medicine,

and certainly for a paper on nutrition

to show up there meant that it had

to meet an exceedingly high standard.

This paper, where Chris is the first author,

it's Gardner et al, 2018 JAMA,

looked at weight loss in people following one

particular diet versus another particular diet.

And this was a 12 month weight loss study.

So it was focused specifically on weight loss,

although they looked at some other parameters as well.

And the basic conclusion of the study was

that there was no significant difference

in weight change between people following a healthy,

low fat diet versus a healthy,

low carbohydrate diet with significantly

more dietary fats in them.

This caused a lot of ripples

in the world of nutrition and nutritional science,

and certainly in the general population,

because anyone that understands diet

and nutrition would immediately say, but wait,

there are all sorts of different implications of eating

one type of diet, say low carbohydrate, higher fats,

versus a higher carbohydrate, lower fat diet.

And indeed there are.

This study was focused specifically

on fat loss and on weight loss.

So as we discuss time restricted feeding,

we need to be very precise

about what are the effects of time restricted feeding,

and of eating in particular ways

at particular times, we are going to emphasize again,

whether or not the study was done in mice or in humans,

in athletes, in men, in women, or both,

but the study from Gardner and colleagues

is a beautiful study,

and really emphasizes that

if one's main goal is simply to lose weight,

then it really does not matter what one eats provided

that the number of calories burned

is higher than the number of calories ingested.

However, anyone out there who understands

a little bit of biology,

or a lot of biology will agree

that there are many factors

that impact that calories burned part of the equation.

Some of those are obvious.

So for instance,

amount of exercise, type of exercise, basal metabolic rate,

how much energy one burns just sitting there.

I've talked before on this podcast

about NEIT, Non Exercise Induced Thermogenesis,

where if people bounce around a lot and fidget a lot,

they can burn anywhere from 800 to 2,000 calories per day.

So their quote-unquote basal metabolic rate

is actually much higher simply

because they're fidgeters,

whereas people who tend to be more stationary

have a lower basal metabolic rate, on average.

There's a great science to support this.

Metabolic factors and hormones

are also very important.

Hormones, such as thyroid hormone

and insulin and growth hormone,

and the sex story to hormones, testosterone and estrogen,

those levels will also profoundly influence

the calories out, the calories burned component

of the calories in, calories out equation.

So if out there on the internet

or in listening to a particular podcast

or speaker, somebody says,

this is the ideal diet,

or calories in, calories out does not

matter, or calories in calories out

is the only thing that matters.

I think it's very important to understand

that there are some foundational truths,

such as calories in, calories out,

but that of course,

hormone factors and the context in which

a given diet regimen is taking place

are exceedingly important.

A good example of this would be puberty

at that time in life,

sex steroid hormones are changing profoundly

in the body as our growth hormone and other hormones.

And much of caloric intake

is directed towards protein synthesis,

towards the production of muscle and bone

and other tissues of the body.

And that's because of changes in hormones

that we call puberty.

So, there's no way that we can drill

into every aspect of a given feeding plan

or feeding schedule that would allow us

to tap into every aspect of the list

that I read out before weight loss,

fat loss, muscle organ, genome, epigenome,

inflammation, exercise, cognition, mood, and lifespan.

But today, we're going to be very precise

about how time restricted feeding,

it's very clear from both animal studies

and human studies

can have a very powerful and positive impact

on everything from weight loss

and fat loss to various health parameters.

This is a beautiful literature

that's emerged mostly in the last 10 or 15 years.

And as we march into this literature,

what you'll see is that there actually

is a perfect diet for you on a given day.

And that perfect diet for you on

a given day is contextual,

meaning it depends on what you did yesterday

and what you're going to do tomorrow.

So there is a perfect diet for you.

And today, I'm going to arm you

with the mechanisms and understanding

that will allow you to define what

that perfect diet is

and will allow you to eat on a schedule

and to eat the things that are going

to best serve your goals.

So let's talk about eating and what happens when you eat,

and let's talk about fasting, or not eating,

and what happens when you fast.

I did an entire episode on eating

and metabolism, and hormones and other factors

that impact appetite.

We don't have time to go into all those details now,

although you're welcome to listen to that episode as well,

but we can briefly describe the overall conditions

that are set in the body when we eat

and when we don't eat.

The key word here is conditions.

If I can emphasize anything today, it's that what you eat

and when you eat it set conditions in your body,

and those conditions can be very good for you,

or very bad for you, depending on when you eat.

In fact, when you eat is as important as what you eat.

I'll repeat that, when you eat

is as important as what you eat,

at least as it relates to health parameters,

in particular, liver health and mental health.

Some simple rules about eating.

First of all, when you eat, typically your blood glucose,

your blood sugar, will go up.

Also, insulin levels will go up.

Insulin is a hormone that's involved

in mobilizing glucose from the bloodstream.

How much your glucose and insulin go up

depends on what you eat and how much you eat.

In general, simple sugars, including fructose from fruit,

but also sucrose and glucose,

and simple sugars will raise your insulin

and blood glucose more than complex carbohydrates.

Things like grains, and breads, and pastas, and so forth,

and grains, and breads, and pastas, and so forth will raise

your blood glucose more than fibrous carbohydrates,

like lettuce, and broccoli, and things of that sort.

Protein has a somewhat moderate

or modest impact on insulin and glucose,

and fat has the lowest impact

on raising your blood glucose and blood insulin.

So what you eat will impact how steep a rise

in blood glucose and insulin takes place.

And there are a number of factors

that are related to your individual health

that will also dictate how steep

and how high that rise in glucose and insulin will be.

For the time being, I'm leaving

out people who have type one diabetes.

These are people that don't manufacture their own insulin,

and type two diabetes is essentially insulin insensitivity,

lack of sensitivity to insulin,

which leads to high blood glucose.

But, when you eat,

blood glucose goes up and when you don't eat,

blood glucose and insulin go down.

The longer it's been since your last meal,

the lower, typically,

your blood glucose and insulin will be.

And the higher, things like GLP1, glucagon-like peptide 1,

glucagon being a hormone that's also secreted

when you are in a fasted state or a low blood glucose state.

It's involved in mobilizing various energy sources

from the body, including fat through what we call lipolysis,

also using carbohydrates,

and potentially even using muscle as a source of energy.

So, that's kind of a fire hose

of information about what happens

when you eat and don't eat,

but just think of it this way, blood sugar

and insulin go up when you eat,

they go down when you don't eat,

and other hormones go up when you don't eat.

So there are hormones associated with the fasted state,

and there are hormones associated

with the eating and having just eaten state.

Now, the most important thing

to understand is that, like everything in biology,

this is a process that takes time.

So insulin and glucose go up when we eat,

and it takes some period of time

for them to go down,

even if we stop eating,

they will remain up for some period of time,

and then go back down, it takes time.

This is very important,

because if you look at the scientific literature

on fasting, on time-restricted feeding,

it's absolutely clear that the health benefits,

not just the weight loss benefits,

but that the health benefits

from time-restricted feeding,

occur because certain conditions

are met in the brain and body for a certain amount of time.

And that gives us an anchor

from which to view what eating

is in terms of how it sets conditions in the body over time.

And if that sounds overly analytic, I promise you,

this is the simplest

and best way to think about any eating schedule

or any eating plan.

So I think it's fair to say that in the field of nutrition,

there are a few landmark studies that serve

as really strong anchors for building our understanding

of what to eat and what not to eat

and when to eat, depending on our goals.

The Gardner study that I mentioned earlier

is one such study,

in that it says if your goal is weight loss,

it really does not matter what foods you consume,

provided that you consume a sub-maintenance, caloric diet.

However, I want to emphasize again,

that sets aside issues of adherence,

meaning how easy or hard it is to adhere to a given diet.

Some people find it much easier

to follow a high fat, low carbohydrate diet.

Some people fall follow

a different diet because it's much easier

for them to follow.

And some people are concerned

with mental performance and athletic performance.

So that study doesn't say there's a best diet,

what it says is that what you consume

is less important than the amount of food that you consume,

at least for sake of weight loss,

not necessarily for sake of health.

Now, the study that I'm going

to refer to next is what I would consider

the second major pillar of nutritional studies.

This is a truly landmark study

that was carried out by Satchin Panda,

who is a professor at the Salk Institute

of Biological Studies in San Diego,

an absolutely phenomenal institution,

and an absolutely phenomenal researcher.

I've known Satchin for a number of years,

and I want to emphasize that the current literature

on intermittent fasting

and time restricted feeding can largely

be attributed to Satchin

and the work that he's done.

There are others involved too, of course.

And of course, time-restricted feeding

and fasting has a rich history that goes back many hundreds,

if not thousands of years in different cultures

and religions,

but the science of time-restricted feeding can really mainly

be attributed to the incredible work that Satchin has done.

And I'm grateful to consider him a friend and a colleague,

and we consulted at length in anticipation of this episode.

I also hope to have him on as a guest in the future.

The landmark paper that came from Satchin's lab

was published in 2012.

This was a paper in mice that set the basis

for studies in humans that came later.

And the title of this paper is time-restricted feeding

without reducing caloric intake,

prevents metabolic diseases in mice fed a high fat diet.

So the title tells us a lot.

It says that what's varied in this study

is not what these mice ate, it was when they ate it.

And there were essentially four conditions

in this study and the results are absolutely remarkable.

So I'm going to walk you through the major results.

What they did is they gave mice access

to different types of food.

There were four groups,

one group of mice had access to just a normal mouse diet.

It would not be a diet that you'd be very interested in.

I confess I've actually tasted mouse chow.

If you work with mice at all, you just have to do it.

At least once it doesn't taste very good,

it tastes like a very bland Graham cracker cookie.

And I confessed that. I only had the tiniest little bit,

but mice like that stuff.

And if you allow them to eat that stuff,

what's called ad libitum whenever they want,

you just keep it in their food. 24 hours a day,

they will eat sometimes,

and then they won't eat it at other times, or in this case,

they also had a condition where they gave them mouse chow in

a time restricted way,

just for a certain number of hours each day,

but about eight hours, or they gave them a high-fat diet.

That was a separate group,

got a high-fat diet at any time they wanted.

So this was kind of the carnival for mice because mice

really like high fat, highly palatable foods.

And so they got a lot of goodies and high-fat in their

food.

And then there was a fourth group that had access to the

high fat diet as much as they wanted to eat,

but only during a restricted time period of each 24 hour

cycle, now mice are nocturnal.

Humans are what we call diurnal, actually,

we're not really diurnal we're crepuscular,

which means that we're most active in the morning and in the

evening, not so much in the afternoon, but nonetheless,

everything I'm going to tell you is true also for humans.

And we know this now from human studies,

one of the most important things to take away from this

study was that mice that ate a highly palatable high-fat

diet, a great tasting diet,

but only during a restricted feeding window of each 24 hour

cycle maintained or lost weight over time, whereas mice

that ingested the same diet, same amount of calories,

but had access to those calories around the clock,

gained weight, became obese and quite sick.

And as an additional second point,

the mice that restricted their feeding window to a

particular portion of eight hours of every 24 hour cycle

actually showed some improvement in important health

markers.

And what was even more incredible is that mice that only ate

during a particular feeding window,

also experienced some reversal of some prior negative health

effects.

So this study really lit up the world and got people excited

about time-restricted eating again.

They use an eight hour feeding window.

The story around that eight hour feeding window is kind of

interesting though.

Not many people know this because it wasn't included in the

paper, and there was no reason to include it in the paper,

not to out anybody,

but it turns out that the reason they used an eight hour

feeding window and not a nine hour or a 10 hour feeding

window,

is because studies of this sort are actually quite demanding

to perform and require the constant presence of the graduate

student,

or post-doc there to ensure that the food is in the cages at

particular times and not in the cages at other times.

And mice are really good at hiding food.

They'll even hide food in their jowls.

And so there's a lot of work that has to be done to prepare

for that eight hour feeding window.

And to make sure after that eight hour feeding window,

there's all the food has been removed from the cage and from

the jowls of the mice and so forth.

And it turns out that the significant other of the graduate

student and or postdoc,

I won't reveal who they were running.

This study forbid their significant other,

the scientist from being in the lab for periods of time,

that were much longer than the 10 or 12 hours that were

required in order to ensure this eight hour feeding window.

So when we hear the eight hour feeding windows are holy,

they are not holy and later,

we are going to talk about how eating for a time that's

restricted to eight hours versus 10 hours versus 12 hours.

For instance,

how that impacts various parameters like health parameters

and weight loss, et cetera.

But the eight hour feeding window was actually created

because of a real world constraint on the research and the

relationship with the researcher performing the research,

not because there's anything holy about an eight hour

feeding window, now

an important point about when the feeding window falls

within the 24 hour cycle,

it is very important that the feeding window fall during the

more active phase of one's day, so for humans,

that's typically in the early part of the day or the later

part of the day,

but not at night, put very simply,

there are a lot of data now

pointing to the fact that eating during the nocturnal phase

of the 24 hour cycle is very detrimental to one's health.

In fact,

when we eat can either enhance our health or can diminish

our health.

When we see light can enhance our feelings of wellbeing or

can diminish our feelings of wellbeing.

I've talked many times before about this,

on the human lab podcast, that during the daytime,

you want to get as much sunlight and other types of bright

light in your eyes as safely possible.

And then you want to avoid light in the middle of the night.

It has detrimental dopamine lowering effects can cause

depression, cortisol increases, et cetera.

So when you view light is as important as the light that you

view.

And when you eat is as important as what you eat, in this

study, they saw something really interesting,

which was that not only did restricting food to a particular

phase of the 24 hour cycle benefit,

things like lean body mass and fat loss and a number of

health parameters that we'll talk about in a moment,

but it also anchored all the gene systems of the body and

provided a more regular stable so-called circadian rhythm or

24 hour rhythm, you may be surprised to learn that 80%,

80% of the genes in your body and brain are on a 24

hour schedule.

That is they change their levels going from high to low and

back to high again, across the 24 hour cycle.

And when those genes are high at the appropriate times and

low at the appropriate times,

meaning their expression is high and low at the appropriate

times.

And therefore the proper RNAs and proteins are made because

DNA codes for RNA, RNA is translated into proteins.

When that happens, your health benefits,

when those genes are not expressed at the right times when

they're higher or low at the wrong times of each 24 hour

cycle, that's when you get negative health effects.

This study showed that when mice restrict their eating to an

eight hour period within the most active phase of their 24

hour cycle,

many of the genes that are associated with these so-called

circadian clocks, these genes have names like PER, BMAL,

CRY1, et cetera,

those so-called clock genes underwent a very regular

entrainment, a locking in to the proper 24 hour schedule.

And while this was in mice,

we now know that this also occurs in humans,

I've said before on this podcast, and I'll say it again,

that light,

and when we view light is the primary way in which these

genes and the clock systems of our body get organized or

entrained, meaning matched to the outside light dark cycle.

So viewing light early in the day and in the afternoon,

and as much as possible all day, great,

ideally that sunlight, avoiding light in the middle of the

night is also great.

It's great because it causes the increases in particular

genes and the decreases in particular genes in every cell

throughout your body at the appropriate times,

the second most powerful timekeeper or zeitgeber, as it's

called, is food, and when you eat, and in this study,

the results they saw underscore this point,

what they saw is that the peaks in these clock genes became

very regular.

And the dips in these clock genes became very regular.

And that led to a whole host of really important,

positive health effects.

Conversely, when mice ate,

whenever they wanted across the 24 hour cycle,

these clock genes became really out of whack and the

negative health consequences were the downstream result of

these changes in these clock genes.

This is now also been shown to be true for humans.

So if you want to be healthy, you want your organ health,

your metabolic health to be in trained properly.

One of the most important things you can do is to,

if you lied at the appropriate times of each 24 hour

schedule and to not view light at other times of that

schedule and to eat at the appropriate time of each 24 hour

day.

Now, again,

there are rare instances that we will discuss when skipping

entire days or entire 24 hour cycles of eating can be

beneficial.

But for now we're talking about schedules of time

restricted

feeding involve a window of feeding that falls during

your more active phase, so during the daytime,

putting aside people that work shift work during the daytime

is when you want to eat.

And this eight hour feeding window provided a very strong

reinforcing signal that combines with light to ensure that

these genes are expressed at the appropriate times.

The short takeaway from this is you probably want to think

about and perhaps even engage in time, restricted feeding.

So, as I mentioned earlier,

when mice can eat around the clock, bad things happen.

And one of the bad things that happens is that the liver

suffers, the liver is involved in all sorts of things,

production of important hormones and other factors related

to metabolism.

And when mice can eat around the clock,

their livers got very sick, fatty deposits in the liver.

Other factors in the liver essentially taken down the

pathway of liver disease, the time restricted feeding,

essentially reversed that or led in many cases to an even

healthier liver conditions, and that's based on this study,

but also additional studies also now in humans.

So restricting your feeding to a particular window,

every 24 hour cycle has clearly been shown now in mice and

in humans to enhance liver health, which is wonderful.

How does it do this, well, it happens because food intake,

as I mentioned earlier,

sets certain conditions in the body that lasts for a period

of time.

Anytime we eat,

whether or not we are a mouse or a human, there's

a period of time that's required for so-called digestion,

but also gastric emptying and other processes related to

breaking down that food and utilizing it.

And that is an active process. It requires energy.

And that process of breaking down food involves certain

cellular functions that if they're ongoing throughout the 24

hour cycle or even extended too far across the 24 hour

cycle, meaning you're eating across a 14 or a 16 hour,

an 18 hour window, that causes serious problems.

And this is now been established because of the fact that it

increases the expression of different proteins and genes in

the body, as such as TNF alpha, IL-6, IL-1.

what are all those things?

They are pro-inflammatory markers.

So the reason that the liver gets sick when you're eating

too often is because inflammatory markers are increased.

These inflammatory markers are not inherently bad,

they're there for a reason,

but they are there in order to respond to certain

challenges, immune challenges,

or the ingestion of food and the breakdown of food.

But then in an ideal circumstance,

they are reduced in the period in which there's no food

present in the digestive tract or in which there's very

little food present in the digestive tract.

So by eating around the clock,

you're making yourself sicker by eating at restricted

periods of time, each 24 hours a day,

you're actually making yourself healthier and you're

activating certain processes that can positively impact both

weight, either maintenance or loss of weight.

We'll talk about weight gain a little later and positively

impacting things like liver health.

Also the expression of different things related to brown

fat, the fat that increases your metabolism.

We will return to this also a little bit later and blood

glucose regulation, so the takeaway from this study,

in fact, there are many takeaways from the study.

It's so wonderful is that liver health,

bile acid metabolism, energy expenditure inflammation,

liver metabolites, many,

many aspects of our health are impacted by when we eat,

not just what we eat, as we move forward,

and we talk about intermittent fasting for eight hour

windows, six hour windows,

12 hour windows for all sorts of different intents and

purposes.

I want to start to establish a foundational protocol that

all of us,

any of us can use in order to maximize your particular

goals.

There are some absolutes within this realm of

time-restricted feeding.

Here are a couple of absolutes that you would want to

consider, first of all,

it pays off in the metabolic sense and in the health sense

and in the weight maintenance or loss sense to not ingest

any food in the first hour after waking and potentially for

longer, so I want to repeat that.

One of the key pillars of intermittent fasting is that for

the first hour

after you wake up and potentially for longer to not ingest

any food, okay,

the second major pillar that's well supported by research is

that for the two and ideally three hours prior to bedtime,

you also don't ingest any food or liquid calories for that

matter.

And we will talk about what it means to break a fast and

whether or not certain liquids,

even coffee and tea can break a fast, et cetera,

in a few moments, but just as a foundation,

it's very clear from the research in humans that not eating

any food or ingesting any calories liquid or otherwise for

the first 60 minutes after waking up each day.

And for the two to three hours prior to your bedtime,

that's ideal for the parameters that we've discussed

earlier,

all the different things like weight and liver health and

metabolic health and so forth.

The two most common questions about intermittent fasting are

when is the ideal time for the eating window?

Is it early in the day,

the middle of the day or later in the day?

And how long should that eating window be?

Should it be eight hours?

We already heard why the eight hour window was first

established.

It was because of these lab conditions and the conditions of

the particular relationship of the graduate student

involved,

or should it be seven hours or six hours or 12 hours.

It turns out that there's some general frameworks that we

can follow in order to answer these questions.

As we move into this portion of the discussion,

I want to highlight a very important reference that just

came out,

literally came out last week in the journal endocrinology

reviews.

And the title of this review is time-restricted eating for

the prevention and management of metabolic diseases.

Although the data in this paper go well beyond metabolic

diseases, this is a paper from Satchin Panda's lab.

It's a very lengthy review with an enormous table

that's beautifully organized that scripts out all the

studies done in humans.

Well over a hundred studies looking at time,

restricted feeding in athletes, men, women, children,

diabetes, no diabetes, et cetera,

with detailed references and description of the outcomes.

I've spent a lot of time with this review,

even though it just came out recently and is a absolute

goldmine resource.

It is also the major resource for everything I'm about to

tell you if you would like to delve deeper into the

material.

So let's deal with this first question of when is the ideal

feeding window, and here again,

we're thinking about a schedule of eating that involves

eating at least once every 24 hours,

not two day or three day or every other day fast.

So it turns out that the answer to the question,

when is it best to eat is actually best answered by thinking

about the other side of the coin,

which is when is it best to fast?

So, because we are fasting during sleep,

it's very clear that it's best to extend the sleep-related

fast either into the morning or to start it in the evening.

Now this might seem kind of obvious,

but it's actually not so obvious.

You could place that feeding window early in the day,

middle of the day or late in the day.

Let's think about what happens when we sleep, when we sleep,

our body undergoes a number of different processes in the

brain and body in order to recover the cells and tissues.

Many of you have probably heard of autophagic,

which is essentially a cleaning up a gobbling up of dead

cells and cells that are injured or sick.

And this is a natural process that occurs,

and it occurs mainly during sleep.

Although not only during sleep,

fasting of any kind does tend

to enhance autophagy.

It is not the only way to create autophagic conditions.

Autophagic conditions can be created simply by following a

sub caloric diet.

And there are other things that one can do in order to

trigger autophagy, but fasting does trigger autophagy.

So when we're asleep,

the bad cells are getting gobbled up and eaten.

And the good cells also are undergoing certain repair

mechanisms mainly related to,

or at least governed by those circadian genes that we talked

about earlier, those clock genes.

So you're already fasting when you're asleep and how deep

you are into that fast depends on how long it was since your

last meal.

So if you fast early in the day,

and you've been asleep for 5, 6, 7, 8 hours,

I would hope somewhere between six and eight hours for most

people is going to be beneficial.

When you wake up,

I mentioned earlier that you don't want to eat for at least

the first 60 minutes after waking,

but were you to extend that fasting to say,

9:00 AM 10:00 AM,

11:00 AM or even 12 noon or later you are taking advantage

of the deep, fast that you were in during sleep.

And certainly toward the end of sleep, now,

why do I say deep, fast?

Well,

because when we eat the clearance of that food from our gut

and the processes in our cells and organs that are related

to digestion,

and the utilization of that food takes about five to six

hours, so if you eat a meal and that meal lasts 10 minutes,

20 minutes or 30 minutes, or even an hour,

and then you stop eating, you've stopped eating,

but you are not fasting at that point.

You can say you're fasting because you're no longer putting

food into your digestive tract,

but you're not in a fasted state.

You are not under conditions of fasting, later,

I'll talk about things that you can do to accelerate the

transition into fasting.

So one thing is certain, that you want your eating window to

be tacked or attached to your sleep based fasting in a way

that makes it easier for you to get into the fasted state

for a period of time.

So we can view that point from the perspective of best,

better and worst, okay?

So if you are like most people and you sleep at night,

you're waking up somewhere around 6:30, 7:00 AM,

or maybe even 8:00 AM.

Let's say you were to push your fasting window out,

such that you started eating at noon,

and then you stopped eating at 6:00 PM.

Well,

then you're not eating from 6:00 PM until let's say your

bedtime is 10:00 PM, but from 6:00 PM to 10:00 PM,

your body is not yet in a fasted state because you just ate.

However,

you're starting to taper into a fastest state before sleep

and then all through sleep.

And until the next morning and late morning,

you are actually in a fasted state, now,

most people find it very hard to only eat in the middle of

the day, so while that's best,

it's ideal for sake of the fasting

related improvements in health,

it is not ideal.

And it's not very applicable to most work and family and

social situations.

Most people eat breakfast with others and,

or eat dinner with others.

Some people eat lunch with others, but in general,

it's hard to restrict your feeding window to just the

absolute middle of the day,

but from a purely health perspective,

in a very objective way, that would be the ideal situation.

Let's imagine a different pattern of eating where the

feeding window starts in the afternoon starts around two or

even 3:00 PM.

Some people don't have much trouble or they can train

themselves to get their feeding window out to two or

3:00 PM, and then they won't eat until 10 or 11:00 PM.

Right, if you do the math,

you realize that that feeding window is still pretty short.

It still constitutes what we would call intermittent fasting

or time restricted feeding.

But assuming that they go to bed around 11:00 PM or

midnight,

they are not actually fasted in sleep because for the first

six hours or so of sleep, maybe five,

but probably more like six hours of sleep,

they're still digesting the food that they consumed a late

in the night.

It does appear beneficial to grab a hold of that

sleep-related fast,

meaning you don't want your feeding window to be too close

to bedtime.

And that's why we came up with this kind of foundational

pillar that I discussed with such an earlier,

which is at least no eating for the first hour after waking,

but also no eating within two to three hours prior to bed.

And because we all need to sleep and sleep is seemingly

important for our health of all kinds.

You want to prioritize sleep,

but because we also have to eat,

then you start to think about this and maybe it's not so

good to push that feeding window too late in the day,

because when you go to sleep,

you're not actually capitalizing on the sleep related

fasting.

Now it's not just the case that it's easiest to fast while

in sleep, although that's true because when we're asleep,

typically we're not hungry or looking for food or foraging

for food or wanting food or trying to resist food.

We're just sleeping.

There is something special about the fasting that occurs

during sleep,

because it's associated with a number of processes that

relate to the so-called lymphatic system,

the movement of lymph like fluids and other fluids through

the brain, and kind of sweeping out a garbage disposal,

if you will,

a clearing out of the metabolic debris and some of the

autophagy that's associated with bad processes in the brain.

So we could do a whole episode on this,

but essentially during sleep, and in particular,

during fasted states of sleep,

we are undergoing a number of automatic seller processes

that clear out debris from our brain enhance cognition,

or at least offset dementia.

This is now well-established as well as a number of the same

processes occurring in the organs of our body.

So what we're starting to see here is that there are a

number of constraints on when you can eat, now,

I would be remiss if I didn't acknowledge the social

constraints and the real life constraints, some of us,

because we want to eat with our family and because our

family or our significant others eat around eight or

9:00 PM, and that's the only time we're together,

You have to eat late in the day.

And that certainly not a sin.

I'm not saying that's good or bad, here

we're trying to establish if you recall, best, better,

and worst.

So from both a practical and a health perspective and a

purely objective view of how intermittent fasting works and

can benefit us, starting to eat each day,

somewhere around 10:00 AM or around noon,

and then allowing a feeding window that goes until six or

maybe 8:00 PM.

That seems to me,

at least based on the data and what I understand about

typical cultures,

where people eat in the daytime and in the evening,

that seems to me like the kind of schedule that will allow

you to get the most out of intermittent fasting,

time-restricted feeding,

but does not set you up to be really out of sync with the

social rhythms in most cultures.

If you think about it from the perspective of say a noon to

eight feeding window,

what you'll find is that you're able to eat lunch with

others.

If you like, or by yourself,

you will be able to eat dinner at a reasonable hour,

at least in most countries, in most cultures,

eating dinner somewhere between 6:30 and 7:00 PM is

typical.

When you say a feeding window, that goes until eight.

That doesn't mean sitting down to dinner at eight.

That means your last bite of food or ingestion of any liquid

calories was at 8:00 PM.

Assuming that you go to bed somewhere between 10:00 PM and

1:00 AM that allows this tapering off,

or this transition from feeding to a fasted state,

and still allows you to capitalize on the special period of

fasting that is sleep-related fasting.

And again,

I want to emphasize that the fasting that occurs during

sleep is vital and eating too close to sleep will disrupt

that fasting related sleep.

Now,

there are a number of caveats and details related to this,

and there's an important caveat in detail related to people

that are specifically interested in increasing or

maintaining muscle mass.

So first let's talk about food volume and food type and how

that relates to whether or not you quickly or slowly enter a

fasted state.

Because clearly when we talk about a feeding window,

that feeding window could include any number of different

foods, it could involve cake and ice cream, pizza,

hamburgers, plants, fruit, whatever it is,

or it could involve just fats or just proteins, et cetera.

There are at least three factors that are going to govern

how quickly you transition from ingesting food to a fasted

state, remember,

as you ingest your last bite or sip of calories,

that's not when the fast begins.

That might be when the fastening begins on your watch or on

one of these apps that I'll refer to later,

which can help you track your fasting and eating windows.

But that's not when it actually begins because your body is

still seeing food.

You're actually carrying around food inside of you,

even though you're not putting into your mouth,

you're still eating in some sense.

So it should be somewhat obvious that very large meals are

going to take longer to digest than very small meals.

So that will impact how slowly or quickly you migrate from a

fed state to a fasted state.

There's no way I can spell out what exact volume of food you

should ingest based on the size of your stomach and et

cetera, but you're all familiar with being extremely full,

very full, comfortably full, somewhat full,

or not feeling full and feeling hungry.

So learning to gauge food volume is important.

Also foods that include some fats or a lot of fats will tend

to slow gastric emptying time.

And depending on the kind of fats,

it could mean that a given meal is digested within three

hours versus five hours.

And more fats might be a large meal with a lot of fats has

been, can take five or six hours.

A smaller meal with less fat is going to be digested more

quickly consuming calories in liquid form is going to mean

that gastric emptying time is going to be faster.

And then of course,

there's the glucose and the insulin aspect to it,

which is that foods that lead to big steep rises in glucose

like pure sugars.

Then your glucose will drop, however,

if they're combined with fats,

then it tends to be a more gradual rise in glucose and it's

more sustained, et cetera.

Fibrous foods will also create a more long lasting sustained

release in glucose.

The important thing here is to establish a feeding window

that you can comfortably manage, okay?

Meaning that on average,

you can obey a six hour feeding window or an eight hour

feeding window or a 10 hour feeding window.

And then to place that feeding window in a social and life

context that you can manage on a regular basis, now,

there are two key points that have been gleaned from the

scientific data about this feeding window and when to place

it.

And this is based on a really important experiment

that Satchin and his colleagues have been doing.

There's a website that they have zero-cost website called My

Circadian Clock, you can go to this website free of cost.

There are a number of important resources there,

but what they've done is they've examined the feeding

behavior of thousands of people.

People will take a picture of the food they're about to eat,

and it enters into their account, maybe your account,

if you create one on My Circadian Clock, and they do this

over many days or weeks,

what's great about this is it establishes

what's essentially called a fetal gram a time in which

people ate.

And a number of important findings have emerged from these

fetal grams, across large populations of people,

different time zones with different schedules, et cetera.

First of all,

almost everybody underestimates their feeding window.

Meaning people who think that they are on an eight hour

feeding window or six hour feeding window, when their data

are analyzed,

it almost is always the case that they're actually on a

feeding window

that's one or even two hours longer than they think you

think, well,

how could that possibly be if people are taking their first

bite at noon and they're taking their last bite at 8:00 PM?

Well,

that must mean that they are on that feeding window of eight

hours.

And it turns out that people cheat,

but they don't cheat in any kind of obvious way.

They might have, you know, a glass of wine after dinner,

or they'll have a cup of tea and a little bite of a cookie.

And so when people are honest and they are honest,

in most cases for this experiment,

what you find is that most people's eating window is

actually quite a bit longer.

So in discussing this with such in and reviewing the

literature,

it's clear that if you'd like to be on a 10 hour feeding

window,

that you should probably select an eight hour feeding

window,

because there's always a little bit of a taper on either

side of that eating window.

Very few people are extremely strict about these eating

windows.

It's just hard to do in the context of life events and

social gatherings and, and family and so forth.

Okay, so as we build forward,

your ideal fasting slash time-restricted feeding schedule,

we now have several different rules that we can list out

first,

at least no food for the first hour after waking up at least

one hour, two, no food intake

for two and ideally three hours

prior to your bedtime.

Three, if you want to select an eight hour feeding window,

then you should probably focus on a six or seven hour

feeding window because in reality,

your feeding window is going to be longer reality,

meaning real life constraints.

And if you'd like to be on a 10 hour feeding window,

you should probably select an eight or a nine hour feeding

window,

because the way it plays out is that people almost always

eat outside of their eating window, somewhat.

The other nice thing about selecting a slightly shorter

eating window than is comfortable for you is that it takes

into account that as you take your last bite or your last

sip of calories, there's this time or taper before,

which you are actually in a fasted state.

And because you're eating different things on different

days, presumably some foods leave your gut more quickly.

Some things spike your insulin and your glucose more than

others.

Sometimes you eat more fat, sometimes less fat.

This allows you to fall well within the margins of the

benefits of time-restricted feeding that had been

demonstrated in humans,

which generally involve an eight hour window or so.

So I think this eight hour window or six hour window is a

good thing to shoot for most people, some people,

and we will discuss the exceptions,

but some people truly are exceptions to this.

They just require more food.

And along those lines,

I just now briefly want to touch on some of the studies that

have looked at using a very short feeding window of about

four hours, nowadays,

a number of people are doing the so-called one meal per day,

or are restricting their feeding window to just four hours

or six hours.

And that turns out to be an interesting strategy and the

data around it actually are a little bit surprising.

One surprising thing to leap out of this massive literature

review on time

restricted feeding in humans is that relatively short

feeding windows of say four to six hours do produce a number

of positive health effects.

Things like increased insulin sensitivity,

which we know is good, remember type two

diabetes is a reduction in insulin sensitivity improvements

in beta cell function and the pancreas decreased blood

pressure,

decreased oxidative stress decreases in things like evening

appetite.

So positive health effects and psychological facts in

general.

However, they either produce no change in body weight,

or they tend to produce even increases in body weight, now,

of course there's variation between individuals and between

studies, but this is somewhat surprising.

So the eight hour feeding window seems to be very beneficial

across almost all the parameters that we've discussed,

inflammation, weight, loss, fat loss, et cetera,

and adherence.

I should mention people's ability to stick to the diet seems

quite good on this eight hour feeding windows,

but when people try and undergo very short feeding windows

of four to six hours,

it seems that they are overeating in that four to six hours,

at least overeating with respect to their metabolic needs.

Now,

the contrast to this is the so-called a one meal per day

schedule, very few studies on one meal per day,

one meal per day, unless it's a very, very long meal,

a sort of feast typically would not last four to six hours

because it sort of depends on how you define a meal.

But when you look at the very few, I should emphasize,

again, very few studies on one meal per day.

People typically maintain or lose weight on the one meal per

day schedule.

So what we can say is that the seven to nine hour feeding

window produces all of the major health benefits of

time-restricted feeding as well as being pretty

straightforward for most people to adhere to on a regular

basis and on a regular basis,

turns out to be very important.

I'll get back to that point in a moment.

Whereas the four to six hour eating window doesn't seem to

serve people as well as say a seven or eight hour eating

window,

simply because people are overeating during that eating

window and the one meal per day,

while perhaps ideal for certain people's schedules may

actually cause people to under-eat.

And in some cases that might be what people want.

They actually want to under-eat.

But when we start thinking about in work and in sport,

and when we start considering hormone health and hormone

production, fertility,

that's when we can really start to look at the seven to nine

hour feeding window versus the four to six hour feeding

window versus the one meal per day type feeding window with

some different objectivity,

we can start to look at it through a different lens because

it turns out that when you place the feeding window and how

long that feeding window is actually will impact a number of

other things in particular hormones,

that can be very important for a number of things related to

sex and reproduction can be related to performance at work

performance in athleticism.

And there are excellent studies on this.

So let's explore those now.

So let's talk about some conditions where having the feeding

window early in the day would actually be very beneficial.

There was a study that was published recently in Cell

Reports, again, Cell Press Journal,

excellent journal peer reviewed, very stringent,

from Aoyama, et al,

so this is AOYAMA, et al.

This was published just recently in July, 2021 that looked

at the distribution of protein intake in different meals

delivered either early in the day or later in the day.

And I'm summarizing here quite a lot,

but I should mention that this study was performed in both

mice and humans, same paper,

mice and humans and involved hypertrophy training,

essentially increasing the weight bearing of given limbs to

try and induce hypertrophy,

which is the growth of muscle tissue.

It does appear that muscle tissue is better able to undergo

hypertrophy by virtue of the fact that there's better or

enhanced protein synthesis early in the day,

because of the expression of one of these particular clock

genes called BMAL, BMAL,

BMAL regulates a number of different protein synthesis

pathways within muscle cells,

such that eating protein early in the day,

supports muscle tissue maintenance and or growth.

And in this study,

they also looked at the effects of supplementing so-called

BCAs branch chain amino acids,

which is popular in bodybuilding circles and in strength

training circles and BCAs are essential components of a

number of different foods, but can also be supplemented.

The takeaway of this study is pretty straight forward.

However,

the takeaway is if your main interest is maintaining and,

or building muscle,

then it can be beneficial to ingest protein early in the

day, you would still want to obey this,

what we're calling a kind of foundational rule of no,

not eating any food for the first hour post waking or at

least the first hour post.

And the cutoff for when you would want to eat protein would

be sometime before 10:00 AM.

And there I'm averaging across a number of different

situations, but in general,

this BMAL expression is such that let's say you wake up at

7:00 AM.

Your main interest is in hypertrophy or maintenance of

muscle.

Then you would want to ingest some protein sometime before

10:00 AM.

But obviously if you're interested in getting the health

effects of intermittent fasting,

that you wouldn't ingest any food for at least the first 60

minutes upon waking.

Now it's not as if at 10:01 AM a gate slam shut and you

can't generate hypertrophy, of course that's not the case.

However,

it's very interesting that it doesn't matter when the

resistance training,

the load bearing exercise occurs in the 24 hour cycle.

So whether or not in other words,

people are training early in the day or they're training

late in the day.

It still appears that ingesting protein early in the day

favors hypertrophy or that one is better,

or I should say more easily able to access hypertrophy by

way of these clock,

regulated protein synthesis mechanisms by ingesting protein

early in the day, in no way, shape or form

does this study say that ingesting protein later in the day

is somehow bad for you?

It just emphasizes the positive effects of ingesting protein

early in the day for sake of muscle maintenance and or

hypertrophy.

So if you're somebody who is mainly concerned with muscle

maintenance and hypertrophy,

then it may make sense to move that feeding window earlier

in the day.

And certainly there are people out there who are interested

in muscle maintenance and hypertrophy,

who aren't doing intermittent fasting at all,

and that's also perfectly fine,

but this just so happens to be an episode about intermittent

fasting and time restricted feeding.

There are of course,

modes of eating where one eats small meals spread throughout

the day or weights meals differently.

Such that meals early in the day are larger than later in

the day or vice versa.

There are a near infinite number of ways to organize this.

But if you are somebody who is interested in deriving,

the many clearly established health effects of

time-restricted feeding,

and you are somebody who would like to maintain or build

muscle,

then ingesting proteins in the early part of the day would

be important to you at least on the basis of these results.

And therefore that eight hour window that we've

established as more or less ideal shifted to the later part

of the day might not be as beneficial for you.

Now I can just personally say that for me.

When I wake up in the morning,

it's very easy for me to not eat until noon or one or

2:00 PM.

Eating early in the day is actually somewhat of a challenge.

I discuss this point with Satchin,

because we were talking about how is it that one can move

their feeding window or place themselves onto a different

schedule of intermittent fasting.

And it's very clear that one needs to provide a transition

period in order for that to happen,

you should allow yourself a transition period of anywhere

from one week to 10 days in which you shift your feeding

window by about an hour each day or so.

And then once you establish a feeding window that feels

comfortable for you and that you think you can maintain over

time,

that you simply maintain that feeding schedule for at least

30 days, but ideally you would do that indefinitely.

Now this turns out to be important based on data that

they've gleaned from this My Circadian Clock

massive experiment that they've been doing,

where people are entering the times that they're feeding

and, and eating.

Excuse me, anytime we talk about mice,

I always think about feeding

because I come from a background

in my lab, works on both laboratory mice and on humans.

And anytime I think about humans, I think about eating,

but of course they are the same thing.

The interesting thing to emerge from that very large data

set in humans is that when people log their feeding times,

as I mentioned before,

oftentimes they think they're eating in an eight hour

window,

but they are actually eating in a much broader window.

However,

even for people that are very good about restricting their

feeding to a four, six or eight hour window,

if they're very strict about the start and stop times,

and when they ingest calories,

one of the findings that's really been important to note is

that almost every individual has a lot of drift in when that

eating window resides in their 24 hour period.

In particular on the weekends,

people are either extending or shifting their feeding window

in a way that makes it seem that they've traveled to another

time zone and are eating according to another time zone.

And this is extremely important.

As I mentioned earlier,

based on the 2012 study from Satchin's lab,

where eating at a particular phase of each 24 hour cycle can

help enhance the expression of these clock genes.

If you are eating within a very strict or semi strict

feeding window,

but that feeding window is migrating around from day to day

or five days a week.

You're really organized about when that falls,

let's say for sake of example, from noon to 8:00 PM,

noon to 8:00 PM, Monday Noonday PM, Tuesday, Wednesday,

noon to 8:00 PM, Thursday and so forth.

But then on the Saturday,

it's becoming 11:00 AM and you're ending it early,

or perhaps your starting early in the day on Sunday,

you're having brunch that starts at nine 30 or 10,

and then it's extending out still just eight hours.

But it shifting around that can cause disruptions in the

circadian clock mechanisms that cause disruptions in the

downstream effects of eating that are taking at least two to

three days to recover from.

So obviously we don't want to be overly neurotic about this

stuff, but because this is an episode about the science of

intermittent fasting and time restricted feeding, as

important as how long your feeding window is,

is where that feeding window resides in each 24 hour cycle.

And perhaps even more important than that is that it be

fairly regular where that feeding window resides.

Because even if you have a very short feeding window,

if it's drifting around from day to day,

that actually offsets a number of the positive health

effects of intermittent fasting.

So to really just underscore the way that these different

pieces of the biological puzzle fit together,

if you are very strict or semi strict about your eight hour

feeding window,

but on the weekends that eight hour feeding window is

falling later than it normally would during the middle of

the week.

It is as if you are going to bed later,

even if you're going to bed at the same time,

at least from the perspective of metabolic health,

because of the way that eating impacts these clock genes and

impacts, or I should say subtracts,

the sleep-related fasting that you would normally experience

if you were to finish eating that a couple hours before

bedtime, so again,

we don't want to create any overly obsessive or neurotic

focus on this, I think that most,

all people could benefit from a time-restricted feeding

schedule,

but they should really think hard about what they can stick

to on a regular basis and understand that they tend to

underestimate the feeding window,

that they actually are partaking in,

and that they should place that feeding window in a portion

of the 24 hour cycle that they can be consistent on most

days, and I want to emphasize most again,

because we are not laboratory mice.

We don't have a graduate student coming in for eight hours a

day because that's what their significant other will allow

them to do.

And then removing the food from our jowls and from our

cages, we have access to food pretty much, 24 hours a day,

along those lines, however,

there are things that we can all do that will allow us to

offset some of the drift if you will,

that we experience or that we induce in terms of when our

feeding window occurs or that the feeding window might push

out a little later and then therefore start a little later,

the next day, there are things that we can do in there,

things that we can take.

And so I'd like to discuss those briefly.

So throughout this episode,

I've more or less been alluding to the fact that when you

eat, there's some period of time afterwards in which you're

actually still eating,

at least from the perspective of metabolism,

because glucose is up,

insulin is up and you're undergoing different metabolic and

digestive processes that don't really speak to you being in

a fasted state, right?

It's not just about when you take your last bite or your

last sip.

However,

there are things that we can do to accelerate the transition

from a fed state to a fasted state.

And so I'd like to discuss what those are.

And I want to emphasize that the term fed state is probably

a better way to think about it than eating or not eating

because we think of eating the verb, we're eating,

we're eating, okay, we're done eating I'm fasting now,

but you're not actually fasting you because you are fed.

So we should really think about fed and unfed states because

from a seller processes perspective and from a health

perspective,

that's actually what your body and your system are paying

attention to.

And by now with everything that we've laid out,

I think that should be intuitive to understand.

So there's a fun and exciting concept related to this,

which is glucose clearing.

You may have heard the old adage that if you take a 20 or 30

minute walk after dinner,

that it accelerates the rate at which you digest that food.

And indeed it does, clearing out of glucose from your system

can be accomplished through a number of different means,

but light movement or exercise does increase gastric

emptying time, so for instance,

if you were to eat a meal that ended at 8:00 PM,

and then plop to the couch, watch TV,

or get on your computer or go to sleep,

it would be five or six hours until you have transitioned

from a fed state to a fasted state.

However,

you can accelerate that considerably by taking a 20 or 30

minute just light walk, it doesn't have to be speed walking.

It certainly doesn't have to be jogging,

but just walking outside or moving around.

So glucose clearing is an important aspect of the transition

from the fed state to the fasted state.

And just a light walk can allow you to do that, now,

if you can't get outside,

some people will go through the gymnastics,

literally of doing things like air squats and pushups and

things like that, and indeed,

those will increase the expression of things like glut four

and things that mobilize glucose into muscles and things of

that sort, but, you know, under most conditions,

most people aren't doing push-ups after dinner,

or certainly who've had a big meal,

just taking a light walk can be beneficial.

In addition, you could consider doing intense exercise.

Now you wouldn't necessarily want to do that immediately

after eating.

So let's take a look at what high-intensity training of any

kind does to blood glucose, because in this case,

it turns out that when you do high intensity training

actually has opposite effects on blood glucose,

depending on whether or not you do it early or later in the

day.

So a fairly recent study looked at so-called hit training,

high intensity interval training,

which of course can take many different forms.

It can take the form of circuit training with weights.

It can take the form of, you know,

burpees and pushups and sprints and all sorts of different

things.

But high intensity interval training is typically training

that gets people's heart rates up, you know,

well above 70% of maximum and then brief periods of rest and

then repeating and how long the high intensity interval

training of course will also vary.

There's there are a very brief, you know,

six or 12 or 15 minute workouts.

Some people can carry on with high intensity interval

training for up to 45 or maybe even 60 minutes

in extreme cases.

But when you look at the studies that have explored high

intensity interval training and its effect on blood glucose,

there are a couple of studies that leap out, for instance,

one that emphasized that blood glucose levels will actually

increase if high intensity interval training is performed

early in the day and will decrease if high intensity

interval training is performed later in the day.

Now the purpose for this exploration was not to explore

clearance of blood glucose for sake of intermittent fasting.

It was mainly focused on athletic performance and whether or

not that was better early in the day or later in the day,

et cetera.

But we can extract some information from these studies that

are beneficial for sake of understanding glucose clearing.

If you have ingested food throughout the afternoon and

evening and late in the day,

and you're thinking about going to sleep and you'd like to

enter sleep in a way that is less fed and more fasted,

then engaging in high-intensity interval training in the

afternoon will lower or evening I should say,

will lower blood glucose.

And in that way will help you accelerate your transition

into the fastest state provided you don't ingest something

after the high intensity interval training.

Now is the increase in blood glucose that occurs from high

intensity interval training early in the day,

is that detrimental, not necessarily.

So that oftentimes is associated with the shuttling of

nutrients to the muscles.

They've just done a lot of hard work.

So it's not that high intensity interval training should not

be done early in the day, in fact, for many people,

including myself training early in the day,

just for the way that my psychology and biology works is

always better for me than training later in the day.

And the other important thing to mention is that high

intensity interval training done late in the day can be

beneficial from the perspective of glucose clearing,

lowering blood glucose,

and helping transition from the fed to the fasted state in

preparation for sleep.

However,

if you're ingesting caffeine or anything to engage in that

high intensity interval training in a way that prevents you

from getting to sleep well,

then it's going to be detrimental overall.

So the reason I mentioned this is of course,

because it's nice to know that light walks after dinner or

any other meal for that matter or high intensity interval

training provided it's done in the second half of the day

can lower blood glucose and speed the transition from fed to

fasted states.

But I also mentioned it because what we are really trying to

achieve when we partake in intermittent fasting so-called

time-restricted feeding is what we're really trying to do is

access unfed states or fasted states.

It's not really about when you eat and what you do.

It's about extending the duration of the fasting period

as long as you can,

in a way that's still compatible with your eating, right,

not the other way around.

And this gets back to this key feature of our biology,

which is that what we eat when we eat, when we exercise,

when we view light,

it's about setting a context or a set of conditions in your

brain and body.

So it's not so much about the activities that you undergo.

It's about the activities you undergo and their relationship

to one another over time, and so in this way,

it really beautifully highlights the way that your biology

is interacting all the time light is setting.

When you're going to be awakened,

when you're going to be asleep,

when you eat is going to be determining when you're going to

be awakened, when you're going to be asleep.

And when you eat is also going to be determining when you

are able to clear out debris from your brain and body and

repair the various cells and mechanisms of your body,

when you're able to reduce those inflammatory cytokines

throughout your body.

And this is really the beauty of time research and feeding,

which is, it's not really about restricting your feeding.

It's about accessing the beauty of the fasted state, now,

there are other ways to clear out blood glucose that involve

supplements or prescription drugs.

These are so-called glucose disposal agents, glucose,

disposal agents, such as Metformin,

which is a prescription drug or berberine,

which is an over the counter substance will lead to very

dramatic reductions in blood glucose.

And so they shift you from a fed to a fasted state.

And I know many people who take berberine before eating

meals that include a large number of carbohydrates,

for instance, as a way to clear out glucose.

Now I've tried berberine before.

And what I can tell you is that if you take berberine,

which by the way is very much like Metformin,

its effects are almost identical to Metformin in fact,

but it's much less expensive and it's over the counter.

If you take berberine and you have not ingested

carbohydrates, many people, including myself,

experience a splitting headache,

you become hypoglycemic because it is a glucose clearing

agent.

So if you're going to experiment with things like Metformin

and or berberine or similar,

you want to be very cautious that you're not clearing out

blood glucose, that's already low.

And the dose response for this varies tremendously from one

individual to the next.

And there's a strong circadian component.

So if some people react very well to berberine early in the

day, but find that later in the day,

it provides extreme headaches for some people it's the

opposite.

So I caution you in exploring things like berberine and

Metformin that you should expect to experience a number of

physical and psychological effects that may work for you

might be great for you,

but might also not be great for you, nowadays,

there are a number of commercially available,

continuous glucose monitors, I've tried

one of these, it involves putting what's essentially a patch

with a little needle that goes into your skin,

which is continuing continually, excuse me,

monitoring your blood glucose.

And you can look at it at an app on your phone,

and you can learn a lot that way about how different foods

impact the increases in decrease in blood glucose.

If you're doing experiments with berberine or Metformin,

you can see how those impact your blood glucose.

You can see how exercise hit training or otherwise

impacts blood glucose, excuse me again,

it's very hard to assess blood glucose without a continuous

blood glucose monitor, and if you're not using one,

you're mainly going to be relying on subjective things like,

oh, I feel like I have low blood sugar, or I feel shaky.

Like I have high blood sugar or shaky cause you have low

blood sugar.

So I have to say that glucose clearing agents that involve a

walk or exercise moderate or intense are going to be a lot

easier to titrate and adjust the levels of then things that

you're going to take, where you have to adjust the dosage.

And then once you ingest a certain dosage,

you're along for the ride,

at least until the effects of that particular compound wear

off, it doesn't mean those things don't have utility.

It doesn't mean people aren't using them because many people

are, but they are potentially a very sharp blade

that is a double sided blade.

So I encourage you to approach those with caution.

If you decide to at all,

it's worth thinking about what the low blood glucose state

is and why it's beneficial as well as why it might produce

headaches.

And in some cases can also adjust the effects of other

hormones in the fasted state,

a number of different proteins that are expressed in cells

undergo changes in their expression.

We talked about this earlier, when we are fasted,

we tend to reduce the activity of a particular protein

called MTOR mammalian target of rapamycin.

MTOR is very active in cells while they are growing.

So throughout development,

it's also very active in cancers of various kinds.

MTOR needs to be what's called phosphorylated.

If you don't know what that means, don't worry about it.

But phosphorylation is a manner in which certain proteins

are altered so that they can actually be functional within

cells,

MTOR is associated with cell growth of all kinds healthy

and unhealthy.

When MTOR is phosphorylated, there's a marker called PS6

so phospho MTOR expressed as PM6.

If this is all escaping you, don't worry about it.

Phospho MTOR and PS6 are reduced by fasting.

Now, this makes sense.

If you think about it,

because eating and growth are associated with each other,

fasting is not necessarily anti-growth,

but it is not pro growth, and when we fast,

we see increases in cells of things like AMPK,

the sirtuins, things like transcription

factors like FOX-O,

ATF and ketones or ketone bodies.

You may have heard of the ketogenic diet.

What's the point of all this biochemistry, it's not,

you just blitz you with a bunch of cellular biology and

biochemistry.

It's to say that we have cell growth pathways involving MTOR

and PSX,

and we have cell repair and cell shrinkage processes that

are associated with AMPK, the so-called sirtuins,

which Dr. Davidson Claire

from Harvard and others are famous for

discovering and understanding things like AMPK,

these two different divergent pathways of cell growth and

cell breakdown and repair and by breakdown, I mean,

actual clearance autophagy, and repair.

Those can be triggered by being in either the fed or the

fasted state.

So one way I'd like you to think about the fed state,

not just eating,

but having recently eaten or the fasted state,

meaning high blood glucose and,

or you've recently eat eaten,

or are currently eating or drinking calories,

is that when you eat or when you don't eat, when you're fed,

when you're fasted,

you are either promoting cellular growth of all kinds or

you're promoting cellular repair and clearance of all kinds.

And so, again,

this is about setting conditions in the brain and body.

It's not so much about when you eat food A or B,

it leads to increases in MTOR, anytime you eat any food,

doesn't matter if it's plant-based,

animal-based fat, protein, carbohydrate, doesn't matter.

You are biasing your system towards a biochemical state of

cell growth.

And any time you haven't eaten for a while or blood glucose

is low,

you're biasing your system toward a state of cellar repair.

And this is why people who do not suffer from any blood

glucose regulation issues take things like berberine as

glucose, disposal agents, or take Metformin.

I'm not necessarily suggesting that you do that,

but it's because those things mimic fasting.

They create situations in the body that promote things like

AMPKs, and sirtuins,

and others to push your body and your system

down a route of repair,

even though you might have just eaten a meal an hour ago,

along the lines of the health benefits of intermittent

fasting, there are nice data showing improvements in the gut

microbiome and in particular,

in the treatment of irritable bowel syndrome and other forms

of colitis in time, restricted feeding,

meaning time-restricted feeding seems to be able to assist

people with those conditions,

following the general parameters that I discussed before

eight hours and so forth.

Why and how, well, by way of intermittent fasting,

impacting the expression of these various clock genes,

and because the clock genes impact the mucosal lining the

mucus lining of the gut,

it appears that intermittent fasting can reduce the amount

of so-called lactobacillus that's present in the gut.

And lactose bacillus is when in high levels is correlated

with a number of different metabolic disorders.

At the same time,

time-restricted feeding seems to enhance the proliferation

of some of the gut microbiota,

like acetobacter and some of the other ones that promote

healthy mucosal lining,

and that promote better overall intestinal function.

So these are pathways that have now been established,

and it appears that intermittent fasting isn't just

modulating these processes,

but is actually having a direct effect on the mucosal lining

in a way that favors a healthier gut microbiome.

So it should come as no surprise that many people who

experience gut issues benefit from restricting their feeding

window to eight hours or so per every 24 hour period.

The other very exciting finding about intermittent fasting

is one of the major health issues

these days is the proliferation of so-called non-alcoholic

fatty liver disease,

30 years or so non-alcoholic fatty liver disease was

exceedingly rare to see in the clinic, except in alcoholics,

fatty deposits in the liver are bad.

It is essentially liver disease.

Nowadays children and adults are showing up with

non-alcoholic fatty liver disease.

Some of these people are obese, others are not,

but it's a serious health concern.

And it's growing in numbers all the time.

A recent study that was published in Cell Reports

Medicine just a couple of weeks ago, tested the hypothesis,

whether or not the gut microbiome or so-called brown fat

tissue is impacting the liver health.

And in particular nonalcoholic fatty liver disease.

The short takeaway from this study is that contrary to what

was previously thought, the gut microbiome,

while very important for a number of other processes in the

body doesn't seem to be related to this non-alcoholic fatty

liver disease.

This is surprising to people or should be to those of you

that have been following the gut microbiome literature,

however, brown fat,

which is a healthy fat that we have between our two scapulae

and in our upper neck,

it doesn't tend to be blubbery type fat pads,

but it sits deep to the skin,

but creates a thermogenic effect in the body that is helpful

for reducing the amount of other fat,

the type of fat that we're more typically used to thinking

about and talking about white fat and pink fat that's

subcutaneous fat around the abdomen and so forth.

Brown fat seems to have a direct correlation with the lack

of non-alcoholic fatty liver disease.

What this study showed was that in people that have

diminished concentrations of brown fat,

there is a higher probability of having non-alcoholic fatty

liver disease.

Now the good news is brown fat stores can be increased.

And again, this isn't going to create blubber of brown fat.

This is going to create increased thermogenesis and actually

make people leaner and brown fat has a number of other

important positive effects.

Now,

this is interesting because cold exposure of anywhere from

one to three minutes, two or four times per week,

or maybe even 10 minutes,

two to four times per week can increase brown fat stores.

Also time-restricted feeding has now been tied to the

density of brown fat store.

So time-restricted feeding also seems to positively increase

brown fat stores,

probably because of the way that brown fat stores relate to

epinephrin and adrenaline,

which tend to go up when we're fasted.

What does this all mean?

This means for sake of liver health and for sake of

reducing, or maybe preventing, or even potentially,

I want to underline potentially reversing non-alcoholic

fatty liver disease,

time-restricted feeding also appears to be beneficial.

Many people out there are interested in optimizing their

hormones, and as we mentioned earlier,

insulin is a hormone and time-restricted feeding seems to

have very positive effects on overall insulin profiles and

so forth, but anytime you mentioned hormones,

people immediately seem to leap to the sex steroid hormones,

testosterone, and estrogen,

because indeed they have powerful effects,

both in the short-term and the long-term in terms of our

mental and physical health and performance.

There's at least one study that's explored the effects of

time, restricted eating on performance,

athletic performance, immune function, and body composition.

This was a study by Mauro, et al,

that was performed on elite cyclists.

So I want to point that out.

I was a randomized control trial,

but what's really nice about this study is that it explored

a number of different hormonal parameters in people that

were using time restricted eating,

or that had a more extended eating window.

And they tracked everything very carefully.

And the amount of food they were eating was actually pretty

considerable, 4,800 calories, so that's a lot of calories,

but then again,

they were very active and they've measured a number of

different things related to VO2 max, et cetera,

performance and overall performance at what they did cycling

is not the point that I want to emphasize here.

Although there were some positive effects on their

performance related to time-restricted eating, the point

I want to talk about relates to things that presumably

relate to most, everybody,

which are the effects on things like glucose, thyroid,

hormone, testosterone, sex, hormone, binding globulin,

which can bind up testosterone and prevent the so-called

free form of testosterone,

which is the one that has most of the actions in the brain

and body.

And the major takeaway from this study was that

time-restricted feeding of the same amount of calories as

the so-called control condition, okay, same calories,

but either compact throughout the 24 hour cycle to an eight

hour feeding window or allowing them to eat over a larger

feeding window did lead to significant decreases in free

testosterone.

And I think a number of people will raise their eyebrows to

that and think, oh,

well then maybe time-restricted feeding is not for me.

There are a number of important considerations, of course,

one is while they decrease in free testosterone was

significant.

It's also going to depend on where people start out.

So if somebody has already lower modest levels of

testosterone and it drops by 10 or 20%,

that could lead them into a state of poor performance and

wellbeing, whereas if somebody has higher testosterone,

a decrease will necessarily do that.

So it's important to take that into consideration.

This is why I'm always such a fan of people doing their

blood work and knowing what's going on under the hood for

them, a very change in hormonal profile was cortisol.

So-called stress, hormone cortisol,

of course is also naturally released early in the day in a

healthy way to wake you up and promote alertness,

but you don't want its levels to be too high or to have

peaks in cortisol late in the day,

that's actually correlated with depression and a number of

other untoured things.

I would have thought that by restricting a feeding window to

a particular time each day,

that these hard training cyclists would have undergone

increases in serum cortisol and in fact,

the opposite was true.

They had significant reductions in serum cortisol as a

consequence of time, restricted feeding.

I should mention there were significant reductions in serum

cortisol also in the control group,

but not to the same extent.

And the two groups did differ significantly from one

another.

Now this is important because if you just look at one

hormone testosterone, you'd say, okay, based on these data,

time-restricted feeding is reducing testosterone levels

significantly,

even though the number of calories is quite high and is held

constant across the study, but in fact,

because cortisol is lower,

it may mean that the effects of testosterone or the

reduction in testosterone is offset.

And that's because cortisol and testosterone are always in

this somewhat of a dance in terms of cortisol,

inhibiting the effects of testosterone largely and vice

versa.

So it is interesting and important to look at the total

gallery of hormones.

And they did look at a number of hormones.

They looked at other inflammatory markers.

Those were not increased.

That's not surprising if you remember back to the 2012

Satchin Panda study this early pioneering study on time

restricted feeding.

They saw reductions in stress hormones and in inflammatory

markers in time, restricted feeding mice.

And here, this also seems to be the case in humans.

So the takeaway is for sake of hormone health, time

restricted feeding is compatible with quality hormone

health, even in high-performing athletes,

based on everything we know, and that we've discussed,

I would not suggest that people restrict their feeding

window to less than eight hours,

especially if they're training hard on a regular basis.

And it's not just athletes

that should pay attention to this,

when we are working very hard, when we are psychologically

stressed, when we are studying for exams,

or we are in conflict with somebody on a regular basis,

that creates a stress in the body

that's very similar to that of physical training,

the body and brain don't distinguish between physical stress

and mental stress, it's all nervous system.

Remember that it's just cortisol and adrenaline.

There's no special hormone just for physical stress versus

psychological stress, so again,

in thinking about what sort of feeding window will be right

for you,

we arrive back at this eight hour time been that seems more

or less flexible for most conditions,

even high-performing elite athletes.

And I would say just by logical extension,

even for people that have a lot of stress in their life.

And I personally wouldn't suggest that people who have a lot

of stress in their life where the potential for stress in

their life shorten their feeding window much shorter than

eight hours,

because then you would expect that you would start to

increase some of the inflammatory markers.

You would increase the stress hormones,

and you would be decreasing things like testosterone and

estrogen, some of the sex steroid hormones.

So again, it's all about context and the eight hour window,

it isn't holy,

but seems to be a really useful guide to extract the great

health benefits of which there are many in,

of which we've discussed from intermittent fasting time,

restricted feeding.

And yet that it could still be compatible with decent social

schedules and for maintaining hormone health in keeping with

this,

for women that are trying to maintain ovulatory cycles or

for couples that are trying to get pregnant.

I think it's also important to not create a feeding window

that's too short.

The relationship between feeding and body fat stores and

glucose and leptin and hormones is a well-established one.

And we can summarize it very easily here,

although I've done several episodes related to this

previously on optimizing hormone health.

But basically we undergo puberty when there's enough food

and there's enough body fat that the body fat sends a signal

to the brain called leptin.

That's a hormone that comes from body fat signals to the

brain to turn on puberty that's puberty,

but even as adults for women that are menstruating,

there needs to be sufficient leptin signaling to the brain

in order to maintain ovulation because of the way that the

brain communicates with the pituitary and the ovaries.

Similarly for men fasting or extreme exercise plus

fasting,

we now know reduces testosterone it's impacts are not

exactly clear, however, if you reduce food intake,

either in total calories or in duration too much,

you will suffer a drop in sperm counts, fertility will drop.

And this makes sense.

The body is communicating to the brain,

whether or not conditions are sufficient in the body to

reproduce and to presumably,

and hopefully support the health and wellbeing of those

offspring.

So there's a logical link between body fat and eating and

how much food is available to you and how long it's

available to you and the signals in the brain that allow for

reproductive success.

There are some data that pointed differences in the effects

of intermittent fasting for males versus females.

Those data right now only come from mice,

that study was published by Satchin Panda recently,

we still await the studies in humans.

Some people do not do well on intermittent fasting either in

terms of mood or hormone health.

And so everyone needs to determine for themselves whether or

not having a time restricted feeding window is good for

them.

How long that time-restricted feeding window should be.

I think eight hours is kind of a nice minimum to adhere to

based on everything that we've covered today.

And for some people time-restricted feeding is not going to

be compatible with hormone health, for them,

for them eating more meals spread throughout the day,

presumably smaller meals,

same caloric intake is going to be more beneficial for their

hormones.

This is something that is going to be individual and is

going to have to be determined on an individual basis.

However, if you're going to try time restricted feeding,

I do want to remind you that taking a period of three to

seven or ideally 10 days to transition into it,

not just going,

flipping from eating to three meals a day that span from

6:00 AM to 10:00 PM and suddenly going to an eight hour

feeding window,

but rather winnowing down that feeding window about an hour

or so per day is going to allow the hormone systems of your

body, including leptin the hypocretin orexin system,

which are systems within the body, that signal to the brain,

that food is about to come allowing those systems to adjust

so that you're not overwhelmingly hungry, irritable,

and you're not throwing your whole hormone system out of

whack.

I keep coming back to this eight hour feeding window,

and I want to provide a little more basis for it.

And just to encourage that it's not completely arbitrary.

The lengthy review that I mentioned earlier,

features a number of studies that have used this eight hour

feeding window,

but there's a particular study that I'd like to highlight

mainly because I don't expect people to delve into the full

reference list of the other review.

And this is a study that was carried out

between Satchi Panda's lab

and Krista Varady's labs.

This is a collaboration.

The study was carried out in humans and is entitled effects

of eight hour time restricted feeding on body weight and

metabolic disease, risk factors in obese adults, excuse me.

And this study essentially showed,

I'll just read the conclusions that an eight hour time

restricted feeding produces a mild caloric restriction and

weight loss without calorie counting, so that's key, right?

These people aren't calorie counting somehow just by

adhering to an eight hour window.

They are taking in fewer calories than they're burning off

and clinically it reduced blood pressure.

So I mentioned the study,

not because there aren't many others involving the eight

hour feeding window also in humans,

but because the eight hour feeding window has been tested in

obese adults and non obese adults.

And there are even a few studies in children.

So this eight hour window seems to be a really good rule of

thumb and a kind of anchor around which we can each think

about incorporating time restricted feeding.

There are of course, other patterns of feeding.

And while some people have engaged in longer fasts of 24

hours, 36 hours or more alternate day fasting,

meaning eating one day,

not eating the next day or in some cases eating one day and

eating very few calories, 500 or 600 calories

the next day has been tested.

A few studies have also looked at eating a sort of

maintenance level of calories for five days,

and then taking two days and fast clear through,

or eating very few calories, you know, 300 or 500 calories.

In fact,

there's a sort of a community online of people that are

exploring longer,

fast for sake of trying to offset dementia or reverse

effects of dementia, thus far, at least in my awareness,

there isn't any quality clinical peer reviewed study on that

yet for sake of dementia, although I await those studies,

and if anyone's aware of them,

please send me a link in the comments.

But alternate day fasting has gotten the so-called safe bill

of health.

This has been written up meaning that people didn't suffer

bone loss, they didn't suffer any major detrimental effects.

It does seem that it can create significant weight loss and

can help with obese individuals that it can reduce resting

blood glucose,

and every other day fasting in many cases can produce more

rapid effects on weight loss and reductions in blood glucose

than time restricted feeding, however,

every other day type fasting for most people is not going to

be feasible.

They're just not going to be able to do that for a long

period of time.

And what hasn't really been done is the follow-up to see

whether or not people who do every other day fasting or five

days of eating followed by two days of fasting,

whether or not that leads to a rebound in weight gain,

whether or not that leads to a rebound in blood glucose,

et cetera.

So for now the eight hour feeding window and time restricted

feeding seems to be the most tested,

supported in animal studies and in human studies and the one

around which I think most people should orient

if they're considering getting into time-restricted feeding,

it's also sort of hard to imagine how one could include a

significant exercise schedule or work schedule on every

other day fasting.

Remember, in any study, people are often being compensated,

or at least are incentivized in some way to adhere to the

study.

This is one of the major issues that I have with any study

that says that three or four different diets are essentially

equal in terms of their ability to produce weight loss.

Adherence is very different in the outside world where you

don't have a researcher monitoring you where you're not

logging all your food.

Most people don't do that consistently.

And we can take a little bit of a neuroscience perspective

on this to try and arrive at what the best kind of

organization of an eating plan,

or if we wanted to call it a diet,

we could would be for you.

Many people find it easier to just not eat for certain

periods of each 24 hour cycle than to eat smaller portions,

portion control is very hard for some people,

for other people it's manageable, but people like me.

I don't eat half the croissant.

I don't think it's a real thing, it's not,

it's not available to me, I should say.

Now, of course I could eat just half a croissant,

but I noticed that when I eat the croissant,

because they're so delicious that it creates a rise in blood

glucose a rise in the other hormones and chemicals that are

associated with ingesting delicious, highly palatable food.

And it's actually a lot of work for me to just eat half the

croissant.

There's something that's much more thoroughly satisfying

about eating the entire croissant.

And actually there's something that somewhat satisfying

about not eating the croissant at all.

And just knowing that later I can eat the whole croissant.

Now that's me.

Other people find that they don't have any trouble with

portion control that for them just eating small bits of food

throughout the day is what sets them in the right

psychological and physical state for sake of work,

et cetera.

And I mentioned work and mental focus because one of the

aspects of fasting that have drawn a lot of people to time

restricted feeding and fasting is the clarity of mind that

people get.

When first of all,

they don't have to think about when they're going to eat

because they know when their eating window begins.

They also don't have to think about regulating their

behavior because they already know when they're going to eat

and when they're not going to eat.

Whereas when you're restricting portions,

you actually have to make decisions all the while.

You know, and I think I like many people decide, well,

you know, is that exactly half?

Or could I have like another wrong on the croissant?

This kind of thing. I don't negotiate with food.

That's why I like a time restricted feeding window.

I know I'm going to eat for, in my case,

I use a 10 hour feeding window or so,

and I'll eat the whole croissant.

I just don't have to think about it, now,

the food choices that you make inside of that feeding window

are of course also going to be very important.

Certain foods will increase blood glucose,

such that you're going to get hungrier and hungrier.

Others will maintain lower blood glucose and will allow you

to be more controlled in the foods that you pursue.

Those are all individual considerations that are deserving

of their own entire episode.

But I do want to point out that the advantage of time

restricted feeding is that it involves a lot of the

decision-making in the brain.

The so-called go no-go circuitries of our basal ganglia,

if you want to know this areas that control them.

Anytime we have to restrict a behavior,

that's called a no-go.

Anytime we engage in a behavior, that's a go,

no go behaviors require a lot of what's called top-down

control, and it's very metabolically demanding.

And so time restricted feeding allows you to depart from the

whole no-go go negotiation that you have to undergo when you

have to restrict portions.

And so I think this is a reason why many people have

gravitated towards time restricted feeding and why for

people that don't want to have to think about all that it's

just very straight forward.

One of the more hot button issues out there is whether or

not given equal amounts of caloric intake and equal amounts

of activity and equal amounts of nutrients, et cetera,

whether or not restricting food to a particular window

biases,

more weight loss toward fat loss versus loss of other

tissues, because of course, when we lose weight,

we can lose that from any number of different storage sites

within the body, muscle water, glycogen, or fat.

Now this is such a hot button issue that I almost don't want

to get into it, but I'm going to get into it anyway,

because there are data that are very interesting.

This is covered in the review that I mentioned earlier,

that describes how if people follow a time-restricted

feeding schedule for long periods of time.

So 60 days or longer,

there's some metabolic changes in the way that people

metabolize energy that do seem to shift the system toward

more fat loss relative to burning of other tissues when in a

state of caloric restriction.

And I want to say when in a state of caloric restriction,

because there's really no way to cheat the system,

there's no way that you can ingest far more calories than

you burn or excrete, when I say excrete, you know,

I certainly don't suggest this, but there, you know,

bulimics and other people that have eating disorders will

use laxatives at a way to eliminate food quickly from their

system

so it can't be converted into fat or other forms of energy.

That's a very, in that case, it's a pathological situation,

but in general calories in versus calories out,

as I mentioned earlier as this kind of foundational element,

but in states of caloric restriction,

meaning sub maintenance intake,

time-restricted feeding does seem to buy us more of the

energy burned to compensate for that deficit from fat and

the way it accomplishes it is very interesting.

It turns out that it drives more fat loss by way of

increasing a hepatic lipase.

This is something called LAPC hepatic means of the liver and

lipase, which anytime you hear ASC is means it's an enzyme.

So it seems to increase hepatic lipase.

So it increases the enzyme that metabolizes fat for

lipolysis and energy production and reduces something called

CIDEC, CIDEC.

which is a lipid droplet associated and lipolysis inhibitor.

Now that's a mouthful, no pun intended,

but what CIDEC really is this lipid droplet associated

molecule is it can inhibit lipolysis.

So extended periods of time, restricted feeding,

meaning eight hour feeding window or 10 hour feeding window

that's obeyed for several months or more seems to allow the

system to shift toward burning more fat or rather using a

higher percentage of fat when in a caloric deficit.

Now I doubt that this is going to resolve the truly barbed

wire, almost hairball,

ridiculous online debates about whether or not

time-restricted feeding is better than another feeding

schedule, look,

I don't think any particular feeding schedule is holy.

If you are sub caloric,

meaning fewer calories burned than calories ingested,

you're going to lose weight.

But the data seemed to point to the fact that if you do time

restricted feeding for a fairly long duration of time,

and you maintain that,

that you are increasing these lipases that increase

lipolysis energy use from fat,

and you're decreasing the lipid droplet associated lipolysis

inhibitors.

So it's both a you're removing the break and you're pressing

on the accelerator of fat loss.

I think that this logically points to a case in which using

time restricted feeding with a sub caloric intake seems to

be at least to my mind,

the most scientifically supported way to ensure that a

significant portion of the weight that one loses is from

body fat stores.

Any discussion about fasting would be incomplete without a

discussion about what does and does not break a fast.

However,

there is no black and white answer to that question,

and you should immediately understand why it's because

eating and not eating are not equivalent to fed and fasted.

It depends on when you ate how much you ate and where you

are in your circadian cycle.

We can actually arrive at a simple answer to whether or not

something breaks the fast or not.

Now the technical way to go about this would be to wear a

continuous glucose monitor and to ingest little bits of

food, of different kinds or large amounts of food,

of different kinds and measure blood glucose,

because ultimately blood glucose is the readout of whether

or not your system is in a fed or fasted state.

There are other parameters too, of course,

but that's the dominant one

in so far as the scientific literature says drinking water

will not break your fast drinking tea will not break your

fast drinking coffee,

provided it as black coffee will not break your fast

ingesting caffeine in pill form will not break your fast.

There are other things that won't break your fast.

For instance,

eating one peanut when deep in a fasted state will not break

your fast, eating a whole handful of peanuts might not even

break your fast if you are in a very low glucose state.

However,

if you just finished a meal that included carbohydrates,

or it was a very large meal of any kind an hour ago, yes,

indeed, eating one peanut could break your fast.

So it's all contextual, that's

what's really important to understand,

unless you're going to wear a continuous glucose monitor.

And unless you are going to wear a continuous glucose

monitor and set an absolute numerical threshold for what it

is to break your fast.

I think there are some simple rules that we can follow.

First of all, anything that involves sugar in particular,

simple sugars can potentially break your fast.

And there's actually a study on this,

which shows that if people ingest even one,

one gram of sugar post dinner,

if they had a full meal for dinner that can actually disrupt

the expression of some of the circadian genes related to

fasting and to sleep and sleep related fasting.

Now that's pretty extreme,

almost kind of scary to think about,

but that's how sensitive our system is.

If we already have somewhat elevated blood glucose from a

meal that we ate an hour or so ago,

whereas if we have run for an hour or train hard,

high intensity training,

and we haven't quite reached the beginning of our so-called

feeding window, will eating a small amount of food

take us out of that fast?

Well, depends on what the food is.

If it's mostly fat,

probably not, a number of people out there nowadays

talk about so-called fat fasting,

fat fasting as a way to kind of regal past the stringency of

either eating or not eating as a black and white rule for

feeding window versus non feeding window.

So some people will ingest medium chain triglycerides

so-called MCTs,

or people will ingest fats only until their official feeding

window begins.

So these are sort of how the negotiations that people carry

out tend to go.

But that of course won't increase blood glucose and insulin

as much as carbohydrates will,

protein will have sort of an intermediate effect.

And as I mentioned earlier,

ingesting carbohydrates with some fat will tend to blunt the

rise in glucose and will extend the duration over which

glucose is released.

So we really can't say food X or beverage X breaks a fast,

however, at the extremes, we can say that, for instance,

if you drink a can of soda pop,

unless you just ran an ultra marathon,

you're breaking your fast, okay, eat a piece of pizza,

You're breaking your fast, you eat purely fats, maybe,

probably not.

If you've been fasting for five hours or more strictly

fasting for five hours or more.

So you can start to see where there's a lot of wiggle room

and it's very contextual.

And this is why any posts that you see or any information

that you see that something does or does not break your

fast,

that doesn't place it in the context of when the last time

you ate and what you ate and your activity and your time

within the circadian clock schedule of 24 hours,

it's a sort of meaningless discussion, so in general,

I think what's really useful if you're not going to wear a

continuous glucose monitor is to try and be fairly strict

about when you initiate your feeding window and when you

stop your feeding window and as time evolves and you

establish a more regular routine of eating certain kinds of

foods and not others that are right for you because as I've

emphasized before on this podcast,

and I will continue to emphasize keto works great for some

people, vegetarian keto works great for some people,

carnivore diet works great for other people.

Some people are omnivores, some people are carnivores,

some people are vegan.

All of that is great and fine by me.

Everyone has to establish what's right for them, today,

we've really bypass the discussion about foods of a

particular origin or type animal-based or plant-based.

But all the same rules apply within this thing that we're

called intermittent fasting or time restricted feeding.

So what breaks a fast will depend and what you want to eat

or what you are willing to eat.

That's a totally separate manner from when you eat.

But as we've established, when you eat is vitally important,

some of you are probably wondering whether or not artificial

sweeteners or non artificial plant-based sweeteners like