Dr. Satchin Panda: Intermittent Fasting to Improve Health, Cognition & Longevity | Huberman Lab

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 my

guest is Dr Sachin Panda Dr Sachin panda

is a professor and director of the

regulatory biology laboratory at the

Salk Institute of biological studies

his laboratory has made numerous

important contributions that impact

mental health physical health and human

performance for instance his laboratory

discovered the neurons in the eye and

neurons within the brain that regulate

our so-called circadian rhythm circadian

rhythms are 24-hour rhythms and

everything from gene expression to the

overall functioning of tissues our

levels of mood and alertness our ability

to sleep appetite and much much more in

addition over the last decade Dr Panda's

laboratory has made critical discoveries

in terms of how our patterns of eating

over time impact our biology and our

health in particular his laboratory

Pioneer discoveries related to so-called

intermittent fasting also sometimes

referred to as time restricted feeding

today Dr Panda and I discuss how our

circadian behaviors everything from when

we wake up to when we view light to when

we avoid viewing light to when we eat

and what we eat and when we socialize

and how we socialize impacts our biology

and our psychology energy and how all of

that has a strong impact on our health

during today's discussion you will learn

how restricting your feeding to specific

periods within each 24 hour cycle or

perhaps even exploring longer patterns

of fasting and eating Cycles can impact

everything from the health of your liver

to your gut to your brain and how all of

that impacts things like mood and your

ability to perform cognitive work indeed

today's discussion goes deep into all

aspects of intermittent fasting AKA time

restricted feeding we talk about the

basic science as well as the recent

clinical trials that have explored

time-restricted feeding in a diverse

range of people including men women

children people with diabetes people who

are otherwise healthy and much much more

I'm quite aware that intermittent

fasting is a topic of much debate these

days we go deep into that debate and by

the end of today's discussion you can be

certain that you will have learned all

the latest and all the details all all

made very clear to you thanks to the

incredible expertise Discovery and clear

communication of Dr Panda as some of you

may already know Dr Panda has authored

several important books on the topic of

intermittent fasting and how it can

benefit various aspects of Health those

books include the Circadian code and a

more recent book the Circadian diabetes

code both of which we've provided links

to in the show note captions in addition

if any of you are interested in learning

more about Dr Panda's work including

seeing his Publications and reading

those Publications we're supporting his

laboratory you can do that by going to

his laboratory website which we have

also linked in the show note captions

before we begin I'd like to emphasize

that this podcast is separate from my

teaching and research roles at Stanford

it is however part of my desire and

effort to bring zero cost to Consumer

information about science and science

related tools to the general public in

keeping with that theme I'd like to

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and now for my discussion with Dr Sachin

Panda Sachin Dr Panda so good to see you

again yeah good to see you we are

colleagues still but we used to be right

across the street from one another yeah

yeah you remember those days yeah yeah

so I'm delighted that you're here

um I think we're going to talk about a

number of things mainly

intermittent fasting time restricted

feeding and health but also the many

other things that you're doing just

before we started recording we were

discussing your recent paper in nature

uh that involved recordings from

post-mortem Human retina so maybe if

there's time at the end we can get back

to uh your lab has shown that you can

essentially maintain or resurrect

neurons from

uh dead people in order to potentially

and eventually provide transplants to

rescue Vision in the blind so that's

extremely exciting but of course not the

main focus of today's discussion so

we'll have to uh split it up

um the first question I have is how am I

supposed to Define

fasting and time restricted feeding in

meaning when I go to sleep every night

I'm not eating so in some sense

everybody

is doing time restricted feeding to some

degree or another yeah at what point can

we start thinking about a pattern of

eating as time restricted feeding

so-called intermittent fasting

does it have to do with how regular one

is about the start and stop times how do

you think about defining intermittent

fasting time restrictive feeding and

maybe just to simplify the conversation

is one term more correct than the other

in terms of describing this incredible

pattern of feeding

well you know that intermittent fasting

covers many types of fasting

um so actually it started long time ago

and it's embedded into the history of

caloric restriction

um almost 100 years ago people showed

that if you reduce

calorie intake in a rat then that rat

can live for a long time

and in those experiments the calories

were reduced every single day

and that led to the idea that if we cut

down our calories by 20 percent say then

we can potentially live longer by doing

two things one is preventing is related

disease or even if we follow fall sick

maybe we can accelerate cure

and keep the repair mechanism going so

that we can live longer

but it was very difficult to

count calories every day and reduce

maintain that

um

I must say that it's not that calorie

restriction is impossible or we are not

doing it in fact

a lot of us we do

um count calories in our subconscious

mind means every time you took out it

you took out we take out a soda bottle

or something I'm looking at it okay or

in 60 kilocalo or 30 kilocal or zero

kilocal we are doing that so the point

is it's it's we are doing subconsciously

some kind of calorie

counting but reducing calorie by Twenty

thirty percent every single day is not

possible for many people so then the

idea came in mouse and rat experiment

whether they can eat every other day

um and in fact this every other day

feeding

um also led to very similar almost

equivalent Health Improvement as

continuous calorie restriction

um so then the idea was well every other

day is a little bit hard for humans but

just imagine I would just get to eat

only one day and then another day

then the idea came well for humans can

they eat less for one or two days in a

week

so that led to this pipe two diet where

people can eat for five days and then

two days they have to reduce calories so

that's also

intermittently people are fasting

um then as you know Walter longer also

came with this idea that periodic

fasting maybe four or five days in every

month or two months three months you can

fast or reduce calorie

and he also found many benefits of

calorie restriction was there were those

studies on humans many of the studies

started it in mice but alternate day

fasting five two and

um Walters periodic fasting all of them

have now been done in humans not for

longevity of course because

cannot do this for a long time but for

weight maintenance for reducing some

signs of aging or reversing those things

have been done so all of them have been

done in humans mostly healthy humans and

in some cases people with pre-diabetes

or some aspects of metabolic disease so

that led to the idea that that all these

forms of fasting in which

the total caloric intake on any given

day is reduced for one or more days in a

week a month that became that umbrella

term became intermittent fasting

so if you

look up the scientific literature most

intermittent fasting involves

intentionally reducing calories

for at least one or two days in a week

or

um few days in a month

so when we publish time restricted

feeding

um the initial Mouse experiments and

even now most of the mouse experiments

we want to test what is the impact of

time restriction versus calorie

restriction

so in these experiments we don't reduce

calorie on any day of mouse life so the

mice is the same number of calories as

the adlibitum FED mice

but still they say health benefit so

that's why we call it time restricted

feeding

but since it involves

living without food for several hours

for some people which is it can be very

difficult the initial experiments was

done they were done for eight hours of

feeding and 16 hours of fasting that

kind of became popular and so that

that's why people use the same term as

intermittent fasting and now if you

say intermittent fasting and popular

literature or popular media then people

usually refer to time restricted eating

so now coming back to

how do you define time restricted

fitting

um so the way we have been trying to

Define

experimentally and also in literature is

um

trying to

confine all your energy intake from

solid and liquid food combined within a

consistent window of 8 to 12 hours

because that's something that doable of

course people have done time restrictive

trading with four hours six hours and

some people even try to eat everything

within two hours one meal a day

um but the point is those are not

feasible to maintain for very long time

for a lot of people

one question about the six hour versus

eight hour versus 12 hour feeding window

is it important that the feeding window

begin and end at the same time more or

less yeah and if so how much flexibility

is there so for instance I'm somebody

that

I am not terribly hungry in the morning

I like to drink water usually some

caffeine and electrolytes yeah in the

period before my first meal and my first

meal always lands sometime between

11 and 11 A.M and 12 noon there are

exceptions yeah occasionally I'll have a

breakfast a proper breakfast as it's

called Uh I guess it would be improper

if you're intermittent fasting for me

um but typically 11 A.M or noon is when

I first eat my last bite of food is

typically around I don't know 39 PM

that's what works for me yeah

is that consistency affording me any

benefit separate and let's just leave

aside total caloric number

macronutrients plant-based meat Etc but

is there any benefit to shortening that

feeding window that we are aware of or

extending that feeding window or being

even more rigid about the start and end

of that feeding window

yeah so the start of the fitting window

um that's interesting because the

concept of time history feeding when I

describe animal studies it's feeding for

humans it's eating so the concept

actually came from the science of

circadian rhythm so that means um

our body has an internal timetable

that's present in every cell in every

organ

that pre-programs many

molecular aspects of the cells that

leads to physiology and all that stuff

so that essentially there is a

predetermined timetable for every cell

every organ to do certain things at

certain time

and

the Circadian clocks as

you and I know are more sensitive to

light light is the most dominant

um time Giver so for example when

daylight saving time changes or when we

travel from one time zone to another

time zone we feel kind of crappy because

our daily activities uh out of sync

from our internal clock

so that was known for a very long time

but then around the year 2000 2002

there was a famous experiment by Uli

sibler from

Switzerland what he did he just

Fair demise at the wrong time mice are

nocturnal their night feeders and when

he fed the mice during their time and

the liver clock instead of

following its own routine liver clock

actually started following food so that

means by changing our feeding time we

can change we can tune our liver plot

and subsequently the same experiment has

been repeated many times and when we

repeated that in 2009

and we figured out Yes actually outside

this

brand Center called Supra chiasmatic

nucleus or scn which

is considered the master circadian clock

almost

rest of the brain even

follows when we eat and that came out

from Pierre shambon's lab in Europe

where they systematically looked at even

places that are very close to the asean

for those who are who node or some

medial hypothalamus or paraventricular

nucleus all of this

within a couple of four or five

millimeters of the scn but they were

following food queue

amazing so then

um and now if we think about it so for

example when the daylight saving time

changes just one hour change

um or one hour change in alignment

between our internal time and external

time leads to kind of feeling groggy and

filling not out of Peak Performance for

one or two days

so the rule of thumb is when the time

Giver

changes by one hour then our internal

clock takes at least a day to catch up

so that means if you're flying from

LA to New York uh you're moving through

three time zones then on an average it

will take three uh three days to catch

up with the New York Times for some

people it can be even slower and for

some people it can be two days but the

bottom line is yes there is a

decentrality so then what does it mean

for the body sorry one of the function

of clock is to anticipate when you're

going to wake up for example so the

blood pressure slightly goes up our

heart rate goes up our breathing goes up

similarly for food

almost every organ that is involved in

feeding or eating digestion all of them

have clocks

so even from saliva production that's

the first phase of digestion to

secretion of all the digestive juice and

the stomach and the absorption of

nutrients and liver metabolism

everything the whole village expects one

you're supposed to eat and they're

getting ready

for you to eat the first meal after

fasting for a long time so that's why

it's breaking the fast of breakfast

and when that time changes when you

change it by two or three hours from one

day to another then

um sometimes they're like oh food didn't

come or maybe

um will come at a wrong time we were at

the wrong time and then they will track

the new eating time so suppose say one

day you have been eating every day at

eight a.m

um I ate at 8am is that when you start

yeah

when do you when does your feeding

Windows shut uh 6 p.m so I eat for

around 10 hours okay

um and then one day if I switch to 10 am

then what happens is

a clerk is thinking well the food didn't

arrive at eight but it arrived at 10

maybe tomorrow the food will arrive

somewhere between eight and ten so we'll

be ready around nine

and next day if I come back and eat at

eight o'clock then I may eat but my

clock is not ready to digest that food

so that's why this idea is you have to

be consistent uh to take advantage of

this anticipatory activity of our cloth

in different systems to get the best out

of it is there evidence that those

anticipatory systems and as they relate

to digestion help us better assimilate

our food I would imagine so I mean if

you have the gastric juices that are

going to help digest the proteins fats

and carbohydrates and uh already

deployed at the time when you eat I

could imagine that food will be better

utilized than if you don't so in other

words what is the advantage of having

these anticipatory signals in terms of

potential health benefits the

anticipatory signal is really important

from even even from working up

um

the reason why many people feel not

ready completely when they'll wake up to

an alarm clock because the alarm clock

wakes you up but your body is not

prepared so that slippiness after waking

up to an alarm clock is due to our body

is not prepared for that and then the

best example is when the when

uh the daylight saving time changes

particularly when we have to wake up one

hour early uh what happens people who

have underlying heart condition

um when they're waking up when the body

is not ready your heart is not ready and

all operations from the heart has to

start pumping little bit harder then

there is chance of heart attack and in

fact people have looked at hospital

records and that they find that on those

days and there is a sharp rise in heart

attacks in car accidents and car

accidents too because your brain is not

coordinated so you cannot make those

fine decisions

so that's a great example of

anticipatory activity but coming back to

digestion one thing is

um

and this is something that many people

might have experienced

there are many rhythms in our digestive

system and one of the rhythms is our

look our intestine has this peristaltic

function so it kind of contracts and

expands and that moves forward more food

doesn't move due to gravity so it goes

back and forth and that peristaltic axon

actually slows down at night a few hours

after our last meal and

um so that's why when people eat late at

night for example then that food doesn't

get digested because there is not enough

digestive juice first thing and second

even if it gets digested in the stomach

it doesn't move properly so then the

next morning people get up and think

um of course people consume some alcohol

very often and then they think that this

is Hangover but those who don't consume

alcohol then they have the food hangover

because it doesn't digest so that's one

extreme example where food

at the wrong time

can

um so healthy food at the wrong time can

be crap or junk yeah I've um experienced

that where if I've worked late or I

couldn't eat dinner or something and

then I get home I always debate whether

or not to try and sleep yeah but if I'm

too hungry oftentimes it's challenging

and so for me sometimes consuming

something that at least seems easily

digestible like yogurt or something in a

liquid form

um is better for me than if I eat a meal

I've made the mistake of going to the

refrigerator being super hungry and

eating a bunch of food at 10 or 11 p.m

and then falling asleep and indeed the

sleep

if I'm tired enough can be quite deep

but the next morning I feel just

completely physically and and

cognitively weighed down so I think what

you just described makes a lot of sense

so is it so if someone were to select a

feeding window regardless of whether or

not it falls into classic intermittent

fasting time restricted feeding sounds

like eating your first bite of food and

eating your last bite of food at more or

less the same time each day yeah has

benefits

I have this question you mentioned

feeding versus eating and I think it's

actually not just a grammatical uh

semantic issue

um and here's why

we tend to think about when you take

your first bite of food and then when

you take your last bite of food but of

course Foods digest at different rates

more fat in there is going to digest

make carbohydrates digest slower Etc I

mean there's all these adjustments to

the glycemic index and so forth with

Foods in combination

I is it better to think about not eating

but your fed State and blood sugar so

for instance I often get asked on social

media does blank break a fast so uh and

so I like to think about it

scientifically like okay is does plain

water break a fast no does air break a

fast no

um does one grain of sugar

of sucrose break a fast well probably

not but does one teaspoon of sugar break

a fast well you could say yes but

transiently like so I mean when we're

talking about breaking a fast are we

talking about a rise in blood glucose or

are there molecular signals Downstream

of of a rise in blood glucose that

um cannot be reversed in other words if

I'm gonna eat my first meal every day at

noon and I'm gonna eat my last bite of

food at 8 00 pm and at 9 00 a.m for

whatever reason I have coffee with one

teaspoon of sugar in it

I suppose in the strictest sense I've

broken my fast but maybe by if I went

for a hard run that morning maybe by 9

30 a.m I'm back in a quote unquote

fasted state so what is the fasted State

really because when I'm eating at 8 pm

just to give another example

I'm start fasting at 801 perhaps yeah

but I have my blood glucose is elevated

so I'm not really fasted I'm fed yeah

it's just that I'm not eating the verb

right okay so

um so again I I don't want to get overly

detailed just for sake of getting detail

but I think a lot of the confusion out

there about what breaks a fast yeah is

related specifically to this issue yeah

which is if I eat a whole pizza after

sitting around all day it's very

different than if I eat a whole pizza

after having run a 26 mile marathon that

yeah very different yeah

um metabolically speaking so how should

people think about fasted versus fed can

we be mildly fasted versus severe fasted

can we be

um fed-ish versus very fed anyway I'll

I'll uh stop asking questions now

because they all relate to the same

theme yeah no these are um very

interesting question and then

unfortunately as you can as you have you

might have seen in life the most obvious

questions are often unanswered because

it's so hard to do these damn

experiments because if you really want

to address this in humans you have to

bring humans put them in isolation

just like you said I can now imagine

planning five or six different

experiments each experiment should

involve eight or ten volunteers it's

gender sex

and then do it so it's difficult so now

let's go back to see

how do we let's dissect it in terms of

say indirect calorimetry so for example

indirect calorimetry is based on this

principle that whatever oxygen we

breathe in and carbon dioxide we breathe

out if we can measure these two then we

can figure out whether our body

in total we are not saying whether it's

the liver gut or fat or muscle in total

whether it's consuming glucose or fat as

energy source

the idea is when we fast when we are

without food for several hours

then

ideally our body will tap onto glycogen

first and then do a little bit of fat

and then when the body is mostly running

on fat then that ratio of CO2 to oxygen

will come to 0.7

[Music]

um

but what is interesting is we can do

these experiments in mice so we can go

to mice and ask okay so what happens in

mice so

and mice mice are a little bit very

different because mice are not simply

little people they are the metabolism is

different they

store relatively less glycogen than

humans do in terms of total metabolism

so they

overnight within 12 to 14 hours the rer

respiratory exchange ratio or this ratio

will go from one when the consuming

mostly glucose or carbohydrate as energy

source it will slow down slowly go to

0.7.75

it's after 12 to 14 hours they're kind

of mostly running on fat

so now as we give them food

um within 10 or 15 minutes they are not

actually consuming couple of grams of

food they might have consumed say 100 or

200 milligram of that child so which is

less than say five percent of the food

and then the rer will immediately begin

to rise as if

that small amount of food stopped that

fat burning process and cranked up the

carbohydrate burning process when you

say fat burning process you mean body

fat stores being burned right not

dietary fat correct yeah so it's all

body fat means that that's why I said um

we don't know where that fat is being

burned because we are just measuring how

how much mice is breathing in and out

um so for example it can be from the

Skin So subcutaneous fat or belly fat

but not dietary fat no by that time the

dietary fat is already absorbed and

digested and hopefully it's sitting in

the liver or adipose tissue somewhere

but it's the fattest body fat yes thank

you yeah the reason I ask is that

nowadays I think more than half of the

battles about nutrition that I see

online relate to this issue where I

won't name names but someone will come

along and say low carbohydrate diet

allows you to burn more fat

and the more nuanced people out there

will will say well that's true but

you're also talking about dietary fat

you know the word fat can confuse people

I realize you're not doing that you are

certainly not one of the people guilty

of doing this but indeed you eat more

fat you'll burn more fat but that

doesn't mean you'll burn more body fat

in fact I think the day does say that

under conditions of caloric restriction

you'll actually burn less I hope I don't

I'll probably get I'll probably get um

pitchforks uh through the mail toward me

on on that one but but I think that's

true whereas you know people who consume

carbohydrate can still burn body fat

even though the majority of the fuel

they're burning is from carbohydrates so

yeah so here in this case for example

from mice we know that as soon as they

start eating

um the area goes up

coming back to your question what would

be ideal for us to do the experiment

would be okay so we'll go back to that

and then give the mouse maybe 100

milligram of food

and Mouse runs around in the case and

then we'll continue to measure to see

how long it takes for the mouse to come

back and then

so that's one husband so now let's say

um

let's stay on this and then I'll come

back and talk about non-caloric food and

whether that is considered

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so there is a famous experiment that was

published last year by jotakahasi Islam

and it came out in science

and that relates to caloric restriction

and

we kind of started with this idea we

started to discuss on that the rat

experiments were done with caloric

restriction and researchers get reduced

calorie consumption by 20 or 30 percent

and get that food the rats and then

subsequently mice and they all lived

longer

what is interesting is

in all those experiments the researchers

came and gave this bolus of food at one

time whereas the adlibitum FED mice or

rats they had access to food all the

time so they're eating all the time and

then these rats were given 20 percent

less

and what happens is this mice or rats

then I'm going to take that less food

which is restaurant now and just eat

little bit of lunch and then snack after

three hours or snack after three hours

they double up all that food within two

to three hours maximum four hours food

is gone so they're sort of on the omad

diet the one meal a day yeah they're

almost like in one meal a day three to

four hours food is gone

or you can sit there on

four hours eating or feeding and 20

hours fasting

um so then the question became well

the benefit of caloric restriction as we

know is it due to reduced calorie

or

time restricted feeling or timing there

is a timing component to it that they

are eating all of that within three to

four hours and then there is a long

fasting and this is a difficult question

to answer because now

you have to ask this poor grad students

or technicians to come and split that

food into eight or ten or fifteen

different small portions and then give

them to mice in every two hours

who actually published the first paper

in 2017 showing that most caloric

restrictions I mean he used the protocol

that was used by Kelly restriction field

it actually creates a condition of time

restriction

so he saw that and then he went back and

worked with Engineers to come up with

the smart kids where

he could actually tell he could program

how much food is given to mice at what

time of the day or night completely

programmed

so then he took this uh for example

suppose say the adlibitum FED mice it's

five grams of ciao in a day

and if you want to reduce calories by uh

20 percent and the CR Mouse should get

four grams of food

and it divided this into

9 or 10 meals and then give them in

every 90 minutes so in this case they're

eating small

meals

throughout day and night so there is no

fasting so you can say that well this

mouse actually is not getting into

fasting because in every few hours is

getting some food

and then he measured how long the mouse

is going to live

um and he used

um accountments this is a very standard

protocol people count how many mice have

dying on which day and then examine them

to see whether they've died because they

there was an accident or they actually

there was a natural cause

and then they calculate at the end what

is the half life so 50 survival because

that's on an average that's a good

indicator because if there is an outlier

that will live for a long time then that

can skew

so what was interesting was the limit

unfair mice of course they live certain

number of days and then this

caloric restricted mice

that never got into Super fasting but

kind of eating snacking throughout day

and night that also lift 10 percent

extra 10 percent longer so that means

caloric restriction extended lifespan by

10 percent I've wondered about this

because recently

you know there's been there were a bunch

of news headlines about intermittent

fasting and and frankly I was frustrated

if you looked at one major news outlet

they would say time restricted feeding

affords no additional benefit Beyond

caloric restriction for weight loss yeah

then another

popular press venue let's call it that

same study described as time restricted

feeding

doesn't work yeah right and then another

one maybe someplace

um even more extreme you know time

restricted feeding

um only beneficial because of caloric

restriction or something like that so

what you've essentially got are three

different interpretations of the same

data all of which are well two of which

are true one of which is false in my

opinion but what I think people take

away from that is oh time restricted

feeding isn't valuable which is not the

case it I think for many people it's a

convenient way to eat because at least

for people like me it's simpler to

designate between portions of my day

when I'm eating and portions of day my

day when I'm not eating as opposed to

eating portion control for other people

portion control can work but all of that

is related to either maintenance or loss

of weight none of it deals with the

potential health benefits independent of

weight loss yeah right so um and so I I

think that um if we can segment those

out

um obviously in humans it's hard to know

if a given treatment or experiment is

extending life because you don't really

know how long people would live anyway

yeah right whereas with mice you have

some sense of when the mortality was

likely to occur so what can we say about

time restricted feeding and longevity in

terms of biomarkers or in terms of any

other indication that people who start

and stop their feeding window at a

consistent time somewhere between 8 and

12 hours per 24 hour cycle are

tilting the scales towards living longer

as opposed to living shorter this

example of this news article that you

mentioned is really interesting because

that relates to Joe's Joe takas's study

because I described that if you split

calories and eat throughout the day

throughout day and night then the mice

lived 10 percent extra

but if you now give Mouse the same

caloric restricted diet

and fit them during day time

whether within 12 hours or two hours

then the mice lived 10 percent extra

beyond that yes so twenty percent so

okay so let me make sure I understand so

that uh so that I make sure I understand

if you take a certain number of calories

and you distribute them throughout the

24-hour cycle yeah

it's caloric restriction the mice will

live ten percent longer yeah if you

however restrict that to the active

cycle of the so for humans the daytime

then

20 then they live 20 percent long twenty

percent so it's not just total caloric

intake yeah meaning it's not just

important to be sub maintenance and

calories for sacral longevity it also is

important as to when in the 24 hour

cycle yeah you eat those calories do I

have that right so now

that's still the story is not over

because this mice were fed during

daytime and they're not supposed to eat

that's right so for us it will be the

equivalent of being on the night shift

and only eating at night but a sub color

sub maintenance calorie diet I guess is

the right way to say it but when he fed

mice during night time when they're

supposed to eat and they're seeing this

getting the same number of calories

within 12 hours or two hours

then the mice left 35 percent longer

than they control 35 longer so scale to

human lifespan which you know we don't

know but but a 35 longer would mean that

um and again no one knows but um humans

now what is the average mortality in the

United States

yeah so it's around 80 it used to be 18

hours slow uh reduce little bit because

of covet but let's take 80 okay so

people are then now living somewhere

between 25 and 35 years longer but I'm

putting some error bars on yeah yeah so

that was um really profound but now you

pointed out um biomarker and other stuff

so now

if you look at any given time within

that experiment and actually Joe went

back and

um had a separate cohort of mice very

similar and so that he could take tissue

samples and of course in this case you

have to sacrifice the mouse

and he looked for

um he did a lot of molecular analysis

with non markers for example hemoglobin

A1c equivalent or glucose control

cholesterol all this stuff

he could not find anything

[Music]

that predicted the benefit of caloric

restriction so that means in this

experiment whatever we know so far the

predictor of longevity none of them

could predict whether this

um

CR only Mouse which throughout day and

night

that Mouse is going to live less than

the night fed mouse that was going to

live 35 25 extra does that mean that

there are biomarkers related to

longevity that we just haven't

discovered yet yeah so that's exactly so

that means whatever we know so far about

biomarkers those

he could not use to predict maybe there

was a lot of noise maybe he wanted he

had to use more number of mice to get

that because you know biomarkers

are not going to predict in every

instance so there is some error

what is also very interesting is if you

look at the body weight and body

composition of all these mice there is

no difference in body weight and body

composition

across all these differences all these

groups so it doesn't matter when they

ate yeah provided they were submit sub

maintenance calorie intake so less

fewer calories than is required to

maintain their weight didn't matter what

pattern of eating they were the same way

yeah so that in many ways seems to mimic

the human studies where they say look it

doesn't really matter whether or not you

use caloric restriction or or you start

your feeding window in the morning or

start your feeding window in the evening

or you

um or you portion control for sake of

weight contr weight loss because you're

taking a snapshot of that and then

another thing with the human study that

we are referring to here

um that in that human study

people are actually already eating

within 10 hours window

habitually when they selected these

people to have them enroll in the study

so they were already eating for 10 hours

and fasting for 14 hours

all participants had to reduce that

caloric intake and they reduced by

almost 25 percent

the CR group continued with 10 hour

sitting window

and the CR plus time restricted group

had to eat the same number of calories

within eight hours so it's just a two

hour difference it's just a two hours

difference okay so that people I just

want to make sure people can understand

so in this human study which is the one

that I felt that the popular press

venues all except one venue

um got either semi-rung or badly wrong

in terms of their conclusion that was my

interpretation anyway was that

either people came into the study eating

basically in a 10 hour feeding window

which goes back to my first question

which is that most people are not eating

in the middle of the night yeah or if

they're on shift work and they are then

they're sleeping during the day anyway

so they're eating in a 10 to 12 hour

feeding window anyway so you're saying

they either did caloric restriction

portion control within the 10-hour

window or another group within the study

eight sub maintenance calories so

caloric restriction CR as we're calling

it the acronym CR but restricted to that

to an eight hour feeding window and they

didn't see any difference in terms of

weight loss yeah but but it's not all

that surprising right I mean if it's

just a two-hour difference yeah exactly

so we have done that experiment in mice

and we don't see

um difference in not only weight loss

many other markers and I was telling you

about this um paper where I told you

that he allowed this mice to eat within

two hours or 12 hours

sub calories diet 2 or 12 2 or 12. yeah

that's dramatic but still he did not see

change in longevity even within those

two so that means

um when you do caloric restriction and

then at least for months and you are

within 12 hours window

um that's that is giving the mice the

best benefit the optimum benefit and

um two three or five or twelve per Mouse

doesn't matter at least for longevity

can we conclude for humans that whether

or not a feeding window is

four hours six hours eight hours or 12

doesn't matter provided that calories

are are similar or same well I won't go

to that extent because we don't know

many of this particularly we don't know

how this sort of eating window will

affect both success because you know we

always think many of this mouse

experiments even that I told you about

those are done only in Mel mice but that

should be changing right because the NIH

I know this because I'm on study section

which is just a bunch of people who

record who review grants is that every

Grant now has to include sex as a

biological variable it's hard to get

away with

um or rather I should say it the way it

should be said which is people are

required

and should want to look at these

phenomena in male and female mice yes

especially if there are differences so

in this case

um there are many I mean there is also

another paper

um in time history repeating that also

came out a big paper showing that they

um thermogenesis was accounting for loss

in fat mass and time just to referred

mice that was also done only in male

mice

um so this is um we are paying attention

to it so we are now doing all of our

studies in male and female and we do see

big differences between male and female

coming back to humans

what typically happens is when you're

trying to do four hours or six hours of

time restricting people will

inadvertently reduce their caloric

intake yeah just because of gut volume I

tried one meal per day and and I felt

like I was eating so much at that one

sitting yeah that it led to a lot of

gastric distress and I got tired after

the meal and part of the reason I like

to do time restricted feeding is I have

more energy yeah and certainly in the

fasted State I feel more energized

especially if I'm ingesting a little

caffeine or something like that

um so people will reduce

um

energy intake and then

some people who are more active they can

actually

unconsciously they may be spending more

energy in their physical activity and

basal metabolic rate all of this

combined than homozy eating

and that can have a very adverse effect

in long term because we know that this

energy deficit and in fact there is a

scientific term for that it's called red

s relative energy deficit in sports

energy deficit in sports okay yeah it's

because nearly 40 percent of athletes

um not the NFL guys but you know a lot

of people who do track and field

um and nearly 40 percent of athletes

actually experience this Reds red S

without knowing can male and female

athletes both men remains Reds so it's

Reds Reds relative energy relative

energy deficit in sports interesting is

the first I've heard this acronym we

have a new acronym folks this is good to

add to it a list of other acronyms but I

so males and females can experience it

so in females I've heard that

um Reds

um can lead to uh eminaria so loss of of

men's of the menstrual cycle yeah so

that's uh so common that uh so prevalent

that in fact many women many female

athletes they take it for granted that

yes if they are more active then they

will lose their menstrual cycle which is

which may be common but it's not normal

or Optimum per health

and even if they don't want to get

pregnant yeah yeah yeah yeah we had an

expert on female hormones come on and

say the very same thing that regular

cycling is a is very important of

ovulatory menstrual cycle is is

important to try and

um maintain yeah yeah so that's one but

then what is really concerning is

um it does affect bone health

and

um in this state people actually over a

long period of time the loose bone mass

and the bone also becomes more prone to

injury micro fracture and fractures

um so again it's a risk means if some

people are trying to eat within very

short time and they're Physically Active

that happens and it also has impact on

means the reason why

these women are losing menstrual cycle

is the

hpg axis is disrupted hypothalamus

pituitary

gonadal axis

and it starts it may start again

Upstream at hypothalamus or pituitary so

that means that HPA axis hypothalamus

pituitary and adrenal axis may also get

disrupted one of the symptoms of Reds is

also depression anxiety bipolar like

symptoms and we know that many

um many athletes experience that we

think that well this this may be just

peer pressure that always trying to

compete and we know that I'm

unfortunately there are few authors who

just can't cope it and there are many

attempted suicide or suicide so this is

a serious issue and

there's also another new topic in the

lab to come up with a mouse model of

Reds and then study it but this is one

risk why we should not reduce our eating

interval to two such to one meal or very

short time because it can have adverse

side effects that we don't know now

um maybe in future we'll figure out when

we systematically study them

there are studies that are published

showing four hours and six hours time

restricted eating has benefits on weight

loss but those are on healthy

individuals and they were in the studies

so the um you know the study team took a

uh well already monitoring the mature

that there was no sudden weight loss or

weight loss below

um some safety level uh so those are

very different from regular people who

are who maybe even normal weight or even

with uh within the healthy range if they

do then they can potentially so that's

why

what we think is eight to ten hours

maybe the ideal spot to begin with and

um once you are physically active and

you are also spending a lot of energy in

physical activity or Sports you can even

go up to 12 hours because in mice we

have done that experiment

um after 12 hours they do get a lot of

benefits not all but so this is 12 hours

of 12 hours of feeding 12 hours of

fasting yeah

um in humans

um again nobody has done systematically

12 hours but there is one study in

Europe

um from tin High Colette lab and Tin

high and I we collaborate so they used

our my security and clock app this is a

research app we developed just to this

is mostly used in time restricted eating

studies

and he had nearly I think he started

with 200 Swiss participants but then at

the end he selected and took very small

number of groups people who are very

um meticulous about recording all their

food and divided them into usual feeling

whatever they wanted to eat whenever

they wanted to eat and they were given

the advice of Swiss nutrition advice

that's given to improved health and

reduce blood glucose almost like

diabetes prevention program in the U.S

and then the other group was given

advice to eat within 12 hours

this is very early on in time

restorating and we thought that the mice

were getting some benefit let's try with

the 12 hours has any benefit

the bottom line is

at the end of three months and six

months what he reported is both groups

lost same amount of body weight

and then there's not too much

significant difference between groups

but both groups actually improved their

health so the bottom line is the Swiss

nutritional advice that he was giving

Which is the standard of care there it

achieved the same amount of weight loss

as just giving people this advice that

eat within 12 hours so one way to look

at it look at the result is like this

and

then he went to more extent and actually

looked at every single meal these people

consumed so they're close to I think

close to 60 or 70 000 meal records and

pictures he went through and then

classified them to say whether these are

good quality food so they call it the

Nova classification one two three four

one is the food that you can almost eat

raw fruits vegetables

um yogurt and dairy products that you

can almost without any preparation

and then second Nova 2 is kind of home

home cooked food that most people will

prepare in few minutes and then three

and then fourth one is the food that you

can never prepare at home

so for example

biscuit or cookies that we usually

purchase and few other things

and usually the Nova 4 are unhealthy

Ultra processed food so which we should

not be eating so the advice is to reduce

Novak for

and what I found was people who got all

this advice

um to improve their nutrition quality

they actually improve their nutrition

quality they reduce their Nova for food

and people who were in time frustrating

the eight within 12 hours they did not

change the nutrition quality

but what is interesting is they both got

the same modest weight loss so that begs

the question that in the maybe tin high

will do this experiment again to combine

nutrition advice with time restriction

and maybe reduce the time to 10 hours

and that might help

um so

12 hours is something that I say

anyone from five-year-old to 100 year

old can do and if you are trying to

maintain weight that might be a good way

and combine that with exercise it'll be

great and and people can more easily

avoid Reds in that way women and for

non-athletes or recreational exercises

sounds like women

if they distribute their calories across

12 hours are less likely to lose their

menstrual cycle yeah so again this is

something that we have to look carefully

they have to be because

we do have the my security and clock app

that many people download and

self-monitor and they share the data for

researchers we won't provide a link to

that by the way it's a great it's a

great tool yeah but once in a while we

do get this input from some women saying

oh I started doing your Timeless routing

and I I'm seeing all these problems and

then I ask them okay so what else are

you doing they're typically improve the

nutrition quality so they're eating only

salad and few and they're trying to

increase the fiber intake and it's

really hard to eat so much of uncooked

food because cooking helps to absorb

more nutrient and then at the same time

they're running five miles every day and

of course all of this combinedly can

lead to Reds like symptom so that's why

12 I think is a good point if you're

combining physical exercise and better

nutrition quality because in mice also

we have seen that if mice are eating

healthy food and they're eating within

10 to 12 hours then they also live

longer than mice that writing healthy

food but Distributing that calorie over

a long period of time and this is um

Rafa di cabbage

finding from NIH he has systematically

done this study with two different types

of diet and in mice and he finds the

same thing that even mice that are

eating within 12 hours they do live

longer than mice that eat randomly even

healthy food

I I recall a recent study I think it was

either published in cell reports or cell

reports medicine forgive me for not

remembering which we'll both of course

cell press journals excellent journals

which explored time-restricted feeding

in the context of low carbohydrate or

non-low carbohydrate diet so it was low

carbohydrate versus low carbohydrate and

time restricted yeah so these all

caloric matched right between groups and

then non low carbohydrate diets those

are more standard uh I think it was

somewhere in the neighborhood of 60 of

calories from complex carbohydrates and

and as I recall the um the greatest

weight loss

remember same calories across groups

folks

um was achieved with low carbohydrate

plus caloric restriction yeah

um and I wondered why all the popular

news venues didn't cover that study um

but that's why I'm bringing it up now I

thought this is really interesting and

um and I'm somebody who's cycled low

carbohydrate diet

um before I find it hard to sleep after

about three or four days of being on a

low starch yeah diet just personally I

so I like to eat some starches yeah

especially if exercising intensely or

working intensely that's just a little

editorial there that

um but look I know many people who do

just feel better on a low carbohydrate

diet but what do you think of those data

because it speaks to the idea that okay

it's not just the total number of

calories it's not just the quality of

those calories

it's the timing of those calories and

maybe carbohydrate restriction in

conjunction with

time restricted feeding might be the

best path for people who are looking to

lose weight

no I I totally agree that when it comes

to nutrition quality quantity and timing

all these three matter nearly 40 percent

of people who maintain healthy body

weight because sixty percent are

overweight and rupees 40 percent of

maintaining healthy body weight and out

of those 40 I would say nearly majority

of them

are very aware about how much dieting

and what quality of food they're eating

so you're really an optimist you're

looking at the 40 of the glass that's uh

or should we say not full

there was a pun intended but the um no

it's a very interesting way of looking

at rather than saying you know why or 60

of Americans obese uh saying why are 40

not obese that's a very interesting way

to look at it yeah I mean um

subconsciously we're always making the

decision inside no means I'm sure that

you are not going and eating um

cheeseburger every day because

um you want to improve yeah right no

yeah exactly I wouldn't feel good yeah I

enjoy a cheeseburger now and again but I

um no not certainly not this stage or

any stage of my life I think that

um

I think people

actually you think the pandemic had a

lot to do with this I think that people

started to take a look at what they were

doing to support or not support their

health generally yeah I know people

gained a lot of weight during the

pandemic other people got really into

fitness I've seen some colleagues but

you've always maintained

um you've always been in good shape

actually the first time I've seen you in

a while you've seem to have aged

backwards so you are a poster uh for

your own um ideas and hypotheses about

time restricted feeding but but I um I

noticed that during the pandemic a

number of people emerged from the

pandemic in better shape other people in

much worse shape it seemed like it was a

it was like a bimodal distribution there

yeah

um

so yeah I get the sense that starting

and stopping eating at more or less the

same time each day even if caloric

restriction is not the main focus yeah

has additional benefits

um

can we talk about some of those benefits

as they relate to the other things that

impact health so for instance if you're

starting and stopping eating at more or

less the same times each day are you

sleeping better are you getting more

predictable

uh shifts in alertness and sleepiness

like can you predict when you'll feel

good enough to exercise yeah maybe we

could talk about that because you of

course

um are well known for time restricted

feeding and the science around that but

also other things as well

um not the least of which is circadian

biology generally so I always think of

the main timekeepers for our system

being feeding light

activity and social connection did I

miss maybe temp and temperature yeah

yeah so how do these combine with one

another and using timing that we begin

and stop feeding is kind of an anchor

Point can we explore that a little bit

yeah so you know we got into this

um beginning and end and then we

you asked for the calorie how much

calorie will break the fast

um

one thing that I want the listeners and

viewers to

bring back to this timing of when wait

when you're breaking the fast because we

equate Health with weight body weight

and

that's when you know we are talking

about nutrition quality and quantity

because both of them have impact

so now let's think about mental health

because a lot of people

do struggle with mental health they have

anxiety or depression

and also

um it's a gut health because there are a

lot of people who also have acid reflux

or heartburn

and we know that acid reflux or

heartburn can be exacerbated by caffeine

intake in empty stomach

those who have acid reflux of heartburn

they're prone to that then having black

coffee in the morning

before any food

um Can upset their stomach so that's why

in those cases it's very clearly that

caffeine for them becomes the trigger

and that's something the food is

supposed to come and then the stomach is

not seeing the food so it's overreacting

producing excess acid and that comes up

to the esophagus and that's what they're

experiencing

so if people have that kind of condition

then maybe they should consider when

they drink their first coffee is

breaking their

overall fast or kind of putting them

putting their health at risk for acid

reflux

the other thing is people who have

anxiety panic attack we know that

caffeine can judge you up especially on

an empty stomach especially on an empty

stomach so for them again

caffeine can be a trigger so that's why

I want to kind of differentiate that

there is this mental health and other

aspects of health and these are two

clear examples where anxiety panic

attack related to brain health

or acid reflux related to our gut health

in those cases

when we consume that caffeine in the

morning can affect so do you avoid

caffeine in the morning no actually here

is the interesting history about

caffeine and this is something I did not

know and I was once invited to this

history of nighttime activity and maybe

we can take a little bit of detour and

talk about night time activity because

that fascinates me as a circadian

biologist

because over the last 200 000 years

means we assume that humans Homo sapiens

evolved 200 000 years ago so we have

been as a species we have been living on

this planet for 200 000 years

and only in the last

you can say a couple of thousand or five

thousand years when we came to control

fire or maybe you can even go back to

100 000 years there is some debate

um so then the question is well

when you control fire and we light it up

the fire

and we could light up whenever we wanted

we can add Fuel and we can stop the fire

when we don't want it

that's the key

ability in humans that differentiates

them from all the other spaces

no other species we can always say yes

there are signs of this intelligent

decision making for example we know many

crows can make decisions many many

animals they kind of figure out

strategize how to get food but

controlled use of fire is something very

specific to Human

and when we started

um controlling fire fire did not

essentially extend the day

because fire created a evening that is

very different from what people did

during the day

and what people used to do during day

they worked a lot means Gathering food

was almost everything that we did

and so in the evening after the after

the after we brought food mostly tubers

or maybe lentils to cook or once in a

while animals so that we can we could

barbecue

um all of these things happen around

Fire and Fire was so expensive that it

was mostly communal fire so if you go

back to for example Maasai and all this

and such sorry

populations that have no access to

electricity and are still living kind of

that historical life

fire is a communal event and they sat

around the cooked food and then what

happened

they did not talk about work they talked

about

um culture they told the sang the danced

they strategize

um that's how politics started

philosophy started science started all

of this things that are very unique to

human civilization started around

fireside chat

so

um in that way if we think about it we

are still doing fireside chat the only

thing is we have the microwave and the

television or social media so now we

chat with our thumbs right so it's still

so we are hooked to that evening

activity because that's when

we are completely free from the pressure

of the work and we want to express

ourselves that's our independent kind so

that's why

most people find it very difficult to do

time resulting and stop eating at six

o'clock because it's in Grand in our in

our even DNA that we want to eat and

socialize in the evening

so now let's fast forward and see what

is the roll of coffee in this and if you

look at Coffee consumption particularly

Cafe where people can come and have

little bit of coffee and socialize it

also started as an evening activity and

this is an

um now we can go back to Istanbul

because that's one place where Coffee

Cafe is started in mid 16th century so

we are talking about 15 40 to 1570

um and that's when uh

I'm sorry I'm forgetting the name of

historians who actually invited me and

uh okay his name is

I must be butchering the name but I'll

try to provide the spelling and the

wonderful thing about social media is

somebody will tell us on YouTube the

proper pronunciation so it's a great

opportunity if you know the proper

pronunciation please put it in the

comments on YouTube I'm actually I'm

even checking right now in my endnote

library it's not picking up that that's

right we'll provide a link yeah so what

happened was

um so coffee was introduced and

um people came and drank coffee and

talked about politics at night at night

at evening and it actually started with

with Sufi branch of Islam because they

are the ones who uh consumed coffee in

the evening and this is the branch of

Islam where they actually sing and dance

and all that happened in the evening

so singing dancing

by the stupid and then here in Istanbul

people started congregating and having

um talk about politics

but then around the same time

um some you know

in Turkey there was a good sizable

number of Muslims who have to do five

prayers a day number of prayers at set

time the first prayer is very early in

the morning

and then they figured out that if they

wake up and immediately have coffee then

they can stay awake for the first prayer

and in that way they felt pretty good

and they woke up I said that's how it

started as a morning drink to stay awake

and kind of get get on with the day

but what happened was I don't know

whether you have ever tried Turkish

coffee it's very thick

yeah a few years ago right before the

pandemic 2019 I traveled to Turkey is

first of all the food is amazing the

coffee is indeed very very thick yeah

and

I have a pretty high caffeine tolerance

yeah

um from drinking so much coffee in yerba

mate over the years and still do I

really enjoy it but um yeah it's it's

very intense and so what you're saying

is that

um

coffee intake started as a way to extend

into the night the ability to extend

into the night at all was because of the

ability to harness fire and then coffee

stimulatory properties were

leverage toward morning

which is essentially like the way I

think about it we did an episode on

caffeine and some uh someone else

Michael Paul and not I described it this

way that you're sort of taking a loan

out on your energy bank account with

coffee you're suppressing the adenosine

system the density makes you sleepy but

that adenosine system will kick in later

so you're you're it's a credit card of

sorts with an interest right right and

the interest being

um an energetic lag that you're going to

experience in the afternoon yeah but

what happened was with the strong coffee

um that gave heartburn and acid reflux

to a lot of people

so then

they started eating something with

coffee and that's how the culture of

breakfast started in Turkey ah so coffee

actually led to the development of

breakfast not the other way around and

that uh yeah so that's very heartening

uh no again no pun intended uh for the

uh the caffeine lovers Among Us uh which

I count myself one of those so

essentially the food before coffee

became breakfast so you kind of

give something to your to your stomach

so it's busy digesting that and then

when the coffee comes in it's not

reacting to coffee and creating

um acid reflux so it wasn't this

fascinating so it wasn't that breakfast

is necessary on its own it was

essentially a buffer against the gastric

distress caused by caffeine at least in

that culture when in that context

um we cannot say that whether the same

thing happened in all over the world

where coffee is not consumed but still

people eat something in the morning you

said you start your um first meal uh of

the day at around eight what time do you

wake up I wake up around six if I

started to six what time do you have

your first caffeine no actually I have

so that's why I brought up this story

because I have coffee after my breakfast

fantastic I'm a big proponent of

delaying caffeine intake for a few hours

after waking for other reasons that my

listeners have heard me talk about

endlessly so I won't bother with that

now but I think um

allowing the suffice to say that

allowing some of the natural waking up

signals to occur and using light to kind

of clear away and adenosine to further

extend an activity is better than using

a stimulant but until a few hours later

this is fascinating because I've never

thought about the link between extension

into the night socialization or

socializing rather feeding and caffeine

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I'm kind of

um speaking what many other researchers

have found and this this particularly

this fireside chat I'm forgetting again

the name of the scientist I think is

from University of Washington Seattle

she went to Africa and kind of recorded

what people are talking of course you

could not understand what they were

talking Twitter and whether or not

Tesla's stock is going up of course no

no just just kidding folks and then came

back and tried to translate and then

figured out that what they're talking

during daytime and in the evening were

very different so

um so so

uh what are they talking about at night

so exactly so this is like they're

talking about matchmaking and talking

about politics and strategizing to

gather food or or

even singing and dancing uh so this is

um if you think if we think about it how

we manage

sunset

to our bedtime

what we do between Sunset and bedtime

affects most of our health

I'm going to think about that for a

moment I totally agree

um and by the way I'm a huge

believer and and I'm in living in great

hope for the idea that

right now I do think that scientists

understand a lot more about the

different stages of sleep slow wave

sleep REM sleep Etc then we do active

waking States like we talk about being

focused or being alert but that's not

those aren't scientific terms as we know

but I do

believe and I've noticed a distinct

difference between the first

eight hours of the day in terms of

cognition and we know that the

catecholamines are at much higher levels

plus court is also dopamine cortisol

epinephrine all of that is really at

much higher levels than in the later

evening

and so this evening time it all it's

certainly in the context of mental

health we know that morning and evening

we are basically different creatures

yeah yeah

so that's why I think in the evening if

you think about it um

again this is uh again another set of

research from

um my good friend Horacio who the

Iglesias yeah oh yeah yeah I'm a big fan

of horacio's another he's a fellow

Argentine so occasionally we riff about

things related to that but he's a

wonderful biologist are you guys

collaborating yeah his kind of uh I say

he's very humble and it's a low profile

but he does amazing amazing research

totally agree he does research that um

we want to know but nobody is ready to

do it because field research is very

difficult to go to the Wilderness or go

to the places where there is no

electricity and then record

um when these people are eating sleeping

or in this case activity exposure to

light that's what Horacio has done and

uh it was this active watch which is

kind of a modern

activity tracker

um but it's a little bit more refined

because it also collects light

information

what I found was most of these

Argentinian Towers who have no access to

electricity

they consistently go to bed somewhere

between three to three and a half hours

after Sunset so this is very important

because we always think that

um our ancestors when they didn't have

electricity as soon as the sun went down

they just went to sleep no

the fire extended the evening so they

were staying awake for three to four

hours

kind of

um you know

decompressing themselves that we say and

then doing all these activities cooking

sharing meals and then they would go to

sleep

and if you look at the slip onset

variability it was very small like

they're going to bed almost within 15 to

30 minutes standard deviation so no

night owls versus morning people exactly

so we'll get to that none of this this

uh I get attacked by for many reasons it

just goes with the business I'm in of

being public facing these days but every

time I talk about viewing sunrise or low

angle sunlight you know getting some

sunlight earlier someone says well I'm a

night owl and they just it's almost like

a a protest of trying to protect

identity it's become this ideological I

I identity related thing I'm a night owl

I'm a morning person and I'm not but

you're telling me that in these cultures

where there is intellectricity but there

is fire people are going to sleep within

all of them within about 15 minutes of

one another yeah so there is no such

thing as a night owl or a morning person

in the context I still actually I asked

him pointedly because uh uh and then he

said no he has not sinned and says

dragged hundreds of people and if we ask

there are many many sleep researchers or

at least the public facing sleep

Physicians or experts they will say yeah

we can say one third of people a night

hour one third of morning and then one

third are in between but yeah they call

them like Bears wolves and you know and

I'm not being disparaging of that idea I

think people really do feel as it as if

they Orient towards one pattern or

another when I was an undergrad student

I never went to bed before midnight and

actually midnight was my going to

bedtime exactly like 11 45 I'll try to

get ready to hit build and then by 12

I'm in bed and I used to get up at six

six fifteen that's a pretty short sleep

with an alarm of course and but then day

time I used to take 45 minutes to one

hour nap and that was regular

like even if uh whenever I got time of

course in college you know you don't

have the whole debt unlike in high

school you don't have opportunity to nap

but in college you can I might have been

one of those kids with this hoodie on

napping on the desk but they come around

and they wake you up yeah but in this

case just come back to the dorm and

um after lunch usually I used to take a

nap

so

um then in grad school

I remember I rarely went to bed before 2

am and I could have clearly said that

I'm a night owl and actually I was a

night owl

it was very comfortable staying up so

late I was very productive doing

experiments writing all this um

manuscripts mostly and

but then afterwards when I looked back

in postdoc when I had when we had our

daughter

um then things started changing because

you have to

put the baby to sleep

and then after the baby sleeps it's

almost when you have a baby your life

revolves around the baby so then we have

to dim down the light

there is no caffeine and alcohol

drinking or any other things after the

baby sleeps because we cannot do too

much noise and others so then I realized

that no I'm actually not a night owl and

I became kind of more normal because I

could go to sleep between 10 and 11.

and

um that's how I thought well maybe this

was very unique to me

but what is interesting is

I have another colleague good friend Ken

Wright Jr Colorado at Colorado and he

also had grad students and

um and postdocs like me who strongly

believed that there were night owls

um just like everybody else

and he took Ken took the whole Lab for

camping and when they were camping of

course there is less light and a lot of

physical activity hiking during the day

and they all went to bed between 9 and

10 30 p.m I love that study yeah what

Sachin just described was a study I

think there were two studies uh there

were two yeah and um what's interesting

as I recall is that after going camping

for a weekend where people awake with

this more or less with the sunrise yeah

and go to sleep a few hours after Sunset

yeah their melatonin rhythms and

cortisol rhythms and sleep wake rhythms

persisted on that schedule for several

weeks despite returning to environments

where there was a lot of artificial

lighting which I find amazing that just

a weekend of consistent rising and um

going to bed with the sunrise and sunset

yeah more or less

allowed a reset that was very long

lasting yeah

so

um actually even in Horatio study he

found that almost all the tobas they

wake up around sunrise time and it's

amazing when I look at the standard

deviation it's like so tight

so take that night owl so-called night

owls I also in graduate school I would

work until 2 A.M I loved it I'd blast

music in the lab everyone was at home

pretty much not everyone but there were

the the night crew and then I'd get in

sometime around

get up or sometime around 9 30 10 and

then get in around 11 and it was no

problem because I was going to stay so

very late and then over time I noticed

I've become more locked to a standard

schedule so I think what we're saying is

that the clock can our internal clocks

can shift yeah but this idea that we are

genetically

biased towards one schedule or another

may need revisiting that's what that's

the conclusion I'm taking from this a

couple of aspects one is um you know

some people are genetically so

pre-programmed because the other flip

side is what is called technically

familial Urban sleep Fest syndrome so

these people

um you can give them caffeine or

whatever but they will fall asleep say

at eight o'clock they cannot stay awake

till nine or ten

and since it's a very strong phenotype

in sleep and circadian rhythm field they

are very well studied so in fact Louis

potashek and ingwifu they were the first

one to track one family like this and

then they figured out there was a

mutation in one of the clock genes

period two that clocked in and that

mutation

um allowed the clock to run in a way

that these people went to bed very early

I guess historically

given these Fireside Chats those people

were probably not contributing much to

their political discussion whatever that

was decided after they went to sleep is

what they woke up into that reminds me

because as you were describing the

difference between nighttime discussions

versus morning discussions is there any

theme to what is discussed in the

morning versus in the nighttime where

people just sipping their eating and

sipping their caffeine and just waking

up

um but is there are there any ideas

about what morning discussions really

consistent morning discussions or

daytime discussions are mostly about

um work and like hunting Gathering or

farming all that stuff and even these

days that's what we do we you know you

go to I go to work and it's mostly one

meeting after another and we're talking

about how means if you're in different

communities and we're solving problems

or your students come with questions you

have your TA or the office hours all

these things work related we're not

talking I mean serious philosophy of

unless you are in a philosophy

department and you are talking about

political science

and also we are not singing and dancing

so that's why the evening activity even

these days are very different and

typically the evening activities uh

where we express ourselves

we express who we are we feel like we

are free and

um you know you and I we have this

academic intellectual Freedom we can

talk about our work just like we are

talking now there are a lot of people

who work for even in tech industry they

may be working for Google and all these

big tech companies

they cannot talk about their work to

anybody else it's all secret it's all

secret so just imagine that staying so

they're spending

more than half of the wake-up time at

work

thinking and doing work but they cannot

talk about that work even sometimes to

their own family members

so then what happens for them

a lot of people also do the same thing

like um the person who is going and

baking in a restaurant or cooking or the

person who is taking trust and driving

or nurses and doctors can't talk about

their patients reality yeah yeah and

some people just don't want to talk

about it it's so stressful they don't

want to bring that stress home

so that's why I always say that from

Sunset until we go to bed during that

time we try to find time for ourselves

people say this is me time the me time

is essentially we want to truly Express

who we are or we want to entertain

ourselves because on the Fireside chart

it's not that everybody was a performer

there are also some audience so we

always switch our roles sometimes we are

performing and sometimes we are

observing so that's what happens with me

time I love this so um maybe social

media time should be restricted to just

maybe a small portion of that evening

time because I would hope that people

would also interact socially within in

the room maybe in a constructive way or

maybe you use that for connect with your

family members whom you love or you can

have some productive discussion or

something so it's it's kind of

interesting I think it's extremely

interesting because I think again this

this conversation about time restricted

feeding is really conversation about

circadian rhythm and sleep wake activity

and human evolution right

um so that's why let's go back to this

um uh Night Owl because uh we we kind of

made a comment that maybe it's not

genetic but this is where I'm still

wrapping my head around because you know

these days

there's some J-1 studies where they're

trying to look at night owls to see

whether there are some genetic Lincolns

and you know sometimes we always think

yeah if you take half a million people

of course you'll find some low side

but going back to this idea that are

some people more sensitive to light

so that it's likely that the same level

of light even in the same household

may make some people stay awake late

into the night whereas other people are

more resistant to light so that they can

go to bed early and since light has

become so prevalent these days and this

tobus story that we are talking about or

people going on camping that is we have

removed that light

um so there is some

um evidence that People's Light

sensitivity particularly the iprgc or

this intrinsically photosensitive

retinal ganglion cell or the simple

speakers the blue light sensors in our

eyes

um there seems to be even one log unit

change in sensitivity as measured by

pupil constriction so for some people a

small amount of artificial light at

night could really shift their circadian

clock yeah wake them up essentially and

then for some it manner yeah I'm very

sensitive to light at night yeah

exquisitely sensitive to it oh so then

you are like a teenager yes in many ways

um I've been told this thank you

um yeah I think

um I have actually switched to using a

red night light but I should be clear

not a fancy high cost red light for sake

of any kind of infrared simulation but a

red party light type light and I find

that was based on reading one study that

we covered in an episode on jet lag and

shift work which was that it seems to

reduce the cortisol

releasing properties of light at night

to use redshifted light yeah so I just

use a red light bulb I actually travel

with one if I go to an Airbnb or a hotel

and I switch to red light and I find

that I fall asleep and stay asleep

throughout the night much more

consistently especially in when I'm in

New environments which always makes it

disruptive to sleep

um it's made an enormous difference in

the depth and duration of my sleep and

um because oftentimes Hotel lights you

know in the bathroom you'll turn them on

you're just you're just getting beam and

you're right some people don't seem to

to be bothered by that I I really

struggle with that yeah and in fact in

Tina's uh right after puberty

um there seems to be a I think that's

when the teenagers become more sensitive

sensitive to light uh and it's very it's

well known that the teenage boys and

girls they tend to stay awake late into

the night and they can stay up to 12 mid

past midnight

although they can stay of that lid that

doesn't mean that their sleep schedule

is reduced their body still needs the

same amount of sleep as other teenagers

so that's why they are more likely not

to wake up at 6 30 or 7 when we expect

them to wake up and go to school

um I have a question and I ask every

circadian related biologists that can

come into contact with this and no one

has been able to give me an answer one

way or the other but I grew up hearing

that every hour of sleep before midnight

was of more value or potency than the

hours after midnight and indeed I find

that if I go to sleep at 9 30 or 10 P.M

I can wake up at three or four a.m

feeling pretty fantastic and ready to

lean into the day but if I get the

equivalent number of hours of sleep

starting at midnight I feel like

complete garbage when I wake up after

five six hours so um is there any truth

to the idea that going to sleep Within

three hours of sunset is somehow better

for our circadian timing mechanisms

well um there are a few things one you

said that you are very sensitive to

light so I assume that you also avoid

bright light in the evening as best I

can yeah as best as you could can and

then what is happening is with a sense

of that bright light your melatonin

levels begin to rise so you are prepared

for Sleep

um of course this is something that we

cannot measure because measuring

melatonin in every one hour or 30

minutes

um is very difficult and there is no

consumer fishing product yet

so it's likely that your your body is

preparing very well under this dim light

to fall asleep and when he was trying to

stay awake and go

sleep at midnight then maybe from

Midnight for the first three or four

hours you are sleeping well but then

after that your melatonin level might be

beginning to fall and it's not only

melatonin in your core body temperature

and then your heart rate and everything

is changing to make you awake but the

Sleep debt that you have accumulated is

pushing you to be in bed so there is

this

tension between the Circadian aspect and

your sleep depth and unfortunately you

cannot have good night of restorative

sleep for the second half of the sleep

because of the tension that makes good

sense yeah so that's why

um you know you are not the only one

means there are many people who who

experience that and in fact a lot of

people think that well this may be the

way I sleep maybe I'm not um I am not

designed to sleep restoratively until

you know I sleep one day just like the

camping trip

and then they realize what it feels like

what you're missing yeah absolutely

um I want to make sure that we talk

about the other aspect of fire which is

uh you had a paper that came out

recently very interesting paper studying

firefighters and time restricted feeding

and firefighters would you share with us

the the general contour and maybe even

some of the specifics of that study

because I think it's very interesting

for for sake of shift workers but for

everybody really to understand these

results yeah so let's go back to shift

workers because

um this also relates to all of us

because

I always say that each of us is a

shipped worker or has lived the life of

a shift worker

um and we have experienced how terrible

difficult it is

um and now let's start with what is the

definition of a shift worker or

um shipped work like lifestyle there is

no Universal definition unfortunately

but there are many European countries

and particularly if you go to

International level organization

um then you'll find some references

different European countries have

slightly different definition which

essentially points to

if you stay awake for two or more hours

during your habitual sleep time and when

they say habitual sleep time they assume

that we are just like you said we are

kind of programmed to slave somewhere

between say 10

pm and then stay in bed and kind of wake

up after 5am

so the idea is if you stay if you're

staying awake for two or more hours

between 10 pm and 5 am

and you are engaged in some activity

whether it's physical activity or

intellectual activity you are not lying

in bed and wondering worrying about

something but actually working so that

defines that's defined as shift work and

you don't have to do it every single day

even if you do it once a week

for 50 weeks

then that itself is enough to disrupt

your physiology and Metabolism Behavior

brain function like a shift worker the

reason is as you discussed

when you change

our external timing queue so in this

case when you travel jet lag or or

traveling across three days

three hours of jet lag will take three

days to reset

similarly if you're staying awake for

two hours extra or if you're waking up

two hours before your habitual wake-up

time then we just don't get wake up and

then be engaged in some activity in the

dark most of us unmends unless you are

wearing a infrared goggles

we turn on light and light resets our

clock so in that way

every time we stay up for two or more

hours even for one night then for the

next two nights our clock is kind of

trying to catch up

so in that way for three days

the day of the disruption and then two

days following the disruption

um a clock is trying to catch up with

the outside time so clock our body is

not on time without clock

so that means almost for half of the

week or half of the Year our clock is

trying to catch up so that's the

definition of shift work so now let's

come back to

Department of Labor Statistics um U.S

government

um they have not been tracking what

percentage of people are doing shift

work accurately because there are many

difficulties in tracking too

but it's generally accepted that one in

five working adults is a card carrying

shift worker card carrying shift workers

means they are nurses

doctors

firefighters

um

and Bakers

um truck drivers

and many in the service industry

so that's one in five so twenty percent

of working adults

then if we think about

all the college students just like I was

doing and you must have done

um they're also deadlines grants granted

lines then we are also experiencing

experiencing the lifestyle of a shift

worker because we are delaying sleep

even if you're delaying sleep by two

hours for most of the college students

for five days and then the weekend you

are trying to catch up that's kind of a

security and disruption going on

then you take 1.5 or 1.6 million new

months

um in the US every year so when the

child is born and that mother is a shift

worker and actually that mother is worse

than a shift worker because

um you know you don't know what time of

the night the baby will wake up and how

many times and there is no weekend

in motherhood

so they're also living the life of a

ship worker

um we don't count many food delivery and

Uber drivers Lyft drivers are shift

workers but they many of them we know

that they live so in that way

we think the actual number of people who

are experiencing the life of a shift

worker is somewhere around 50 percent of

the adults population at any given time

so that's why it's also another point

that you might have heard from people

that will say oh I cannot do time

restricting

because my schedule is messed up or I

work in a different way and

um that comes into play

so that's why we thought

um okay so we should try something on

shift worker

another point is although one in five

people are shipped workers they carry

disproportionately heavier burden of

disease because almost all age-related

disease that we can think of whether

it's high blood pressure usually high

blood pressure starts in 40s or 50s

high cholesterol

um gastrointestinal problem in digestion

um chronic

inflammation of the colon and then even

colon cancer in many cases

and then of course diabetes all of these

are disproportionately more prevalent

among ship workers

but then when you think about clinical

trials whether it's a drug

or a lifestyle

often one of the top 10 exclusion Factor

criteria is shift work so people who are

doing shift work we exclude them from

many of these trials one thing is

most Physicians and most scientists even

people who do shift work they know that

they are their body and mind is so

messed up

that often time even medications may not

help them

and so that's why we don't try new

medication why to take the risk when we

know it may not help them

and then when it comes to Lifestyle

intervention whether it's sleep

extension for example we cannot do

because they are supposed to stay awake

and do their job we cannot ask them to

stay asleep at night

and then physical activity and exercise