What Happens If You Don't Eat For 5 Days?

Hello Health Champions. How is it possible, that  even though food is the thing that keeps us alive,  

millions of people get healthier when they don't  eat for a few days? What are the mechanisms for  

that? How does the body change and cope and adapt  when we don't eat? A lot of people have heard that  

fasting is good for weight loss, but they're still  concerned because there's so much conflicting  

information out there. So today I wanted to  explore these mechanisms of fasting in a little  

bit more detail to really help you understand what  happens when you miss a few meals and how it can  

have such a profound impact on health. In the  first 12 hours, not a lot of changes take place.  

You're going to be using up some of the stored  carbohydrates in your body called glycogen your  

blood glucose will probably drop a little bit  unless the 12 hours is at the end of sleep and  

you're slightly insulin resistant then because  of something called dawn phenomenon you might  

actually see the opposite your body temporarily  makes some hormones in the early morning to get  

you ready for the day and you might see a little  bit of an increase instead as you're using  

up some of the stored glycogen your body will  gradually start shifting its energy metabolism  

into using more fat and a byproduct of that fat  is called ketones now this is barely detectable  

at this point but it's a process that's starting  and what we want to understand about ketones is  

that this is completely normal everyone is going  to gradually shift into this the problem is that  

oftentimes this is confused with keto acidosis  which is a very dangerous condition that's  

completely different that's if you have type 1  diabetes and absolutely no insulin in your body  

your blood sugar shoots up your ketones shoot up  and that's not going to happen unless you have  

no insulin instead what this indicates is actually  metabolic flexibility that as one fuel starts to  

run lower your body starts looking for another one  when you're metabolically flexible your body makes  

use of whatever fuel there is the most of most of  the changes that take place during fasting have to  

do with energy because we're not eating anything  that can turn into energy so energy becomes super  

important the only form of energy your body can  use is something called ATP everything that you  

eat all the food whether it's carbohydrate or  fat or protein it eventually turns into ATP which  

is a very specific molecule and here's how you  can think about this there's an adenosine group  

and we hook on three phosphates and these  are high energy bonds so think of these as  

springs that you take a little package and you  push it onto a spring and it snaps in place  

and now we have energy stored in that spring and  then later if we undo the snap then it shoots  

off and the spring releases its energy and that's  exactly how this works so when the body needs more  

energy for anything or every process that requires  energy this is what happens it pops off one of  

these phosphates the spring releases that energy  and we're left with ATP adenosine diphosphate so  

how does that relate to the stuff we eat well if  you eat a calorie we call it a calorie which is  

often written as a calorie I'm just mentioning  that if you see it written don't get confused  

it's basically the same thing so in one mole  which is a huge number of these ATP molecules  

we have seven calories so that means that one  calorie you eat basically has 10 to the 23rd  

of these molecules it's like a one with 23 zeros  it's a hundred million trillion trillion molecules  

in one calorie and if we break that down to how  much you need per second then you need about 2 300  

trillion trillion of these molecules per  second so these are such astronomical numbers  

but if you think about the fact that you have  somewhere on the order of 40 trillion cells  

that means that every cell makes trillions of  these molecules per second to keep you alive  

so that means we have a lot of these molecules  but it also means that we have to recycle it  

in a hurry so as soon as we pop one of these off  the body is busy putting it back on so the body  

uses energy from food to create a type of energy  that you can put one of these back on and that  

process is called oxidative phosphorylation  that's why we breathe oxygen and that oxygen  

goes to the mitochondria so that we can keep this  process going so the goal of the body is to keep  

almost all of these loaded all the time but  when energy starts running really really low  

now we can even have a few of these become amp  adenosine monophosphate so this is a high energy  

state this is like a resting in between but this  is a really low energy state this really signals  

that we have a lack of energy we're  really running out at this point  

and then there's an enzyme so when this starts  building up then it strongly signals to something  

called AMPK which is basically amp kinase it's an  enzyme that tells the body hey we got to get busy  

finding other energy we got to up regulate  something and the first thing that they  

up regulate is fat burning because when  you're not eating basically all your energy  

or the vast majority of your energy is stored as  fat do you recognize this guy his name is Usain  

Bolt and he has a bunch of world records in sprint  and i was never as fast as this guy but i did make  

it to the top 10 in the world in decathlon which  is another track event and because of that i  

had a very inquisitive mind when i went through  school i would constantly just ask questions to  

try to understand my body and what was happening  so here are some of the questions that i would ask  

i would ask how many times in a day does  this ATP discharge and get recharged by ADP  

so that turns out to be about a thousand to  1500 times per day your entire stock load of  

ATP of adenosine gets reloaded a thousand to  1500 times per day and if we just take the  

number of seconds per day and we divide  that out we find that if you completely  

stopped reloading the ATP if you stopped that  process then you would have somewhere between  

60 to 90 seconds to live before you completely ran  out of ATP so we picked the mid-range of that and  

we call it 75 seconds so the next question i asked  was well what about athletes what about sprinters  

because the 100 meter sprint is the highest  intensity that a human can come up with  

you're moving basically all of your muscles  at the same time at the maximum intensity  

and a baseline energy output for a person is  about 90 watts that's your basal metabolic  

rate but it turns out someone did a full study  on this phenomenon called Usain Bolt and they  

found that he uses up he puts out a maximum  power output of 2619.5 watts don't ask me how  

they came up with that but it was a huge project  apparently but what this means is he uses up 29.1  

times more ATP than the base rate so what that  means the gun goes off and he starts sprinting  

and he makes no more ATP than what he had at  the beginning he has 2.5 seconds left to live  

so that should give you some appreciation  for how incredibly flexible and adaptable  

the body is that you think he's busy  sprinting but every one of his cells  

just up regulated their ATP production by many  many many times basically what this means is  

if he didn't make any more ATP after the gun goes  off he wouldn't even make it to the 20-yard line  

and by that time he'd be dead when you've gone 18  hours without food something we also often call  

skip breakfast now you're much more into the fat  burning mode your body is starting to make ketones  

at a measurable level and we want to understand  that ketones are not just fuel but they're also  

signaling molecules and we'll talk more about some  other signaling molecules here but these signal  

reduced inflammation and improved DNA repair  especially in brain and nervous tissue what we're  

also seeing in the brain is human growth hormone  increases it's starting to go up significantly  

along with something called BDNF brain derived  neurotrophic factor and these two together is  

basically what you want to think of as miracle  growth for the brain they are responsible for  

your body repairing and also making more elaborate  neural networks every time you learn something  

you're making new connections new synapses process  called neurogenesis and this is only possible  

if you have enough human growth hormone and BDNF  another thing to keep in mind is that exercise  

will accelerate this process basically everything  that we're talking about happening with fasting  

will happen more if you exercise as well also  at 18 hours we start seeing just the beginnings  

of something called autophagy which is a very  interesting rejuvenation process in the body we'll  

come back to in a minute does it still sound like  breakfast is the most important meal of the day  

i certainly hope that you'll start to rethink  that idea what's sort of sad is that breakfast  

in bed in many cultures we think of it as the  ultimate in caring the ultimate in pampering and  

what are we getting we're getting sugar and sugar  and sugar and sugar and sugar there's basically  

not a single item here that is not going to drive  your blood sugar and your insulin crazy 24 hours  

without eating now let's talk a little bit more  about this autophagy thing so it barely started  

probably around 18 hours and now it's picking up  speed autophagy means self eating that's literally  

what the word means it does not mean that you have  to do like this guy and start chewing on your arm  

this is happening at the cellular level because  you're not eating because you're not putting any  

resources into the body all the existing resources  become more precious and the body has to learn to  

become less wasteful so think of autophagy as  recycling that you always have a certain amount  

of cleanup going on in the body you have a cleanup  crew but the longer you go without food the more  

the body up regulates it starts recruiting  resources into this cleanup crew so after a  

while you have much much much more resources  going toward recycling and it's cleaning up  

old debris and when you don't have so much now you  have to start being more careful like if you're a  

carpenter and you don't have a whole lot of wood  left now you have to pay more attention to detail  

you can't afford to waste anything and if you have  to pay more attention and be careful now you're  

also increasing the quality of work so that's how  you can think about autophagy the things we talked  

about earlier like ketones and growth hormone and  BDNF they keep increasing at this point and we're  

also going to start talking about a couple of more  of these nutrient sensors and signaling molecules  

called AMPK m-Tor and NAD i often say that the  body is not stupid it is supremely intelligent  

everything it does is for a reason so i want  to guide you through some of the mechanics  

of what happens when we're in a well-fed versus  a starving state and I'll introduce a few terms  

don't try to memorize them or get confused or  worry about it I'll talk you through it I'll  

keep it simple and I just want you to focus on  the overall picture so when we're well fed we're  

in a state of anabolism which means to build  up and if we have fuel from carbs then we're  

triggering a nutrient sensor called insulin  because insulin helps that blood sugar to get  

out of the bloodstream and into the cell where  we can use it so insulin is a message to grow  

and divide and synthesize and store so if we need  to make more cells then they start dividing we  

make proteins and hormones and all sorts of new  good tissues and if we have some energy left over  

then we store the excess as fat for a rainy day  but there are more nutrient sensors and one of  

the main ones is called m-Tor mammalian target of  rapamycin and this one sends the same message but  

it's more specific into the building insulin  is more about the energy metabolism the energy  

dynamics and mtor does respond to carbs as well  but more so to the protein that's going to become  

the building blocks both of these are resources  and when we have resources now we can put those  

into energy production so there's a couple of  more signaling molecules that are called nad plus  

and nadh that feed in to the krebs cycle  or the cycle that produces energy in the  

body in the mitochondria and if we have a lot  of resources then we can make a lot of nadh  

and we can feed a lot of substrate into this  energy production and if we're good at converting  

into nadh then we're not going to find so much  nad plus and this becomes important so remember  

that that nad plus is also a signaling molecule  the opposite of well-fed is starving and if we're  

doing it on purpose it's called fasting now we're  talking catabolism which means breakdown and we  

talked about ampk we mentioned that earlier that  ATP turns into adp and the lowest energy state is  

amp so when we have any amount of amp build up  that's a strong strong signal for ampk which is  

an enzyme that stimulates fat burning and another  thing that ampk signals is this autophagy that  

we were talking about the recycling so again  resources are becoming more precious and ampk  

is one of the strongest signaling molecules  for that and all of these signaling molecules  

relate to each other because it's a smart body  so when we're low energy the ampk turns off the  

mtor which is supposed to build things up and  mtor turns off autophagy so it's just another  

reinforcement we said that ampk stimulates  autophagy well it does it two ways because it  

turns off something that turns it off so it's just  another way of stimulating it and then what about  

exercise well exercise also stimulates ampk so  you really want to think about exercise as almost  

synonymous with fasting virtually everything  that happens with fasting you'll do the same  

effect with exercise or you reinforce the effects  of fasting of course i would never suggest that  

you do only one instead of the other because they  have tremendous complementary benefits for example  

exercise is the primary stimulation for your brain  which you will not get the same stimulation from  

fasting only exercise will also turn off mtor so  this again is another stimulator for autophagy  

remember this other thing we talked about the  nad plus is also a signaling molecule how does  

that work when we have plenty of resources then  they feed into this energy production system  

but when resources are low now we cannot convert  very much into nadh and if we can't convert into  

nadh now nad plus starts building up it's like  a bottleneck this is supposed to turn into that  

but if it doesn't then it starts to stockpile  and this is a very potent signaling molecule  

for certain genetic mechanisms there are certain  genes called sirtuins which have been studied  

extensively and they are basically life prolonging  they are longevity they are survival genes what  

about the safety does everybody need to fast can  everyone fast well we want to understand that it's  

all about balance that we always need to have  a balance between feast and famine we need to  

have certain periods where we load up and store  some things and we need to have other periods  

where we unload and burn some of those things  that we stored the problem is for most people  

they have lived most of their lives in the feast  region there's an imbalance here so can everyone  

fast well you got to figure out where you are on  the spectrum if you have more body weight or more  

insulin resistance than you would like then you  are more on the feast side and you have to start  

moving over more to the famine side you have to  eat fewer meals you could eat less at the same  

number of meals but that's very difficult because  you're not addressing the insulin resistance and  

you're not breaking the pattern of frequent meals  if you are under nourished if you're extremely  

thin there can still be some benefits to fasting  but you can't do very much of it or any at all so  

figure out where you are and start creating some  balance so true starvation is never a good thing  

and it's unfortunate when people are forced  into that but when you say that you're starving  

and it's three hours since you had breakfast  and you say oh god I'm starving I can't wait  

to have lunch that's not really starving that  means you have an imbalance that you have  

taught your body to expect frequent meals and that  you have taught it to depend on carbohydrates so  

it doesn't really know what to do if you don't  feed it all the time another thing I've heard  

is that fasting and keto is a way of promoting  eating disorder that they think that low  

fat and six meals a day that's the way to eat  and anything else is an eating disorder and it  

will lead to anorexia and bulimia well these have  nothing to do with each other because anorexia is  

a mental problem it's an emotional problem based  on a distorted self-image they see themselves in  

the mirror and they're skinny as a rail and they  see a fat person that has nothing to do that's  

not a metabolic problem that's a mental problem  what we're trying to correct is the metabolic  

problems and in the process we're also actually  helping people become more mentally balanced and  

not so dependent on food i would actually turn it  around and say that if you need six meals a day  

if you get light-headed and irritable and cranky  if you miss a meal if you can't focus then that  

is actually what an eating disorder is short  of having a mental problem with the distorted  

self-image if you're needing six meals that's  probably more of an eating disorder so why don't  

you if you have followed my recommendations my  principles for a few months why don't you put  

in the comments if you feel like that has made you  have more or less of an eating disorder and don't  

do it for me do it for the people who are still  concerned and confused at 48 hours your growth  

hormone has increased fivefold 500 percent more  and along with that we're also seeing increases  

in BDNF and ketones and your rate of autophagy  of cleanup is also increasing steadily we want to  

remember that ketones are not just fuel they're  also signaling molecules so they contribute to  

this increase in growth hormone and BDNF we have  one more hormone called ghrelin that also helps  

increase growth hormone and BDNF and that makes  sense ghrelin is your hunger hormone so when you  

haven't eaten for a while your body releases  the hormone that signals hunger it says hey  

you know maybe you just forgot but we haven't been  fed for a while so why don't you go eat something  

and the beauty of that is that it's more of a  reminder so whereas ketones are steady and keep  

increasing the ghrelin is temporary it's more  of a reminder and if you just have a cup of tea  

or you go for a walk that ghrelin is not going  to keep nagging you it's going to go away it's  

going to say oh well i guess there wasn't  any food around we'll try again in a few  

hours or maybe tomorrow so ghrelin is more of a  temporary stimulation but the ketones are going  

to be steadily increasing some more benefits  we see at this time is brain repair increased  

longevity wound healing and cardiovascular  health and these are all things that  

the growth hormone and the BDNF contribute to also  at 48 hours we're going to see some of the lowest  

insulin levels we have seen since we started  and when we lower insulin we lower inflammation  

and if we keep this up if we gradually lower  insulin and reduce insulin resistance now  

we're also reversing all of the aspects of  metabolic syndrome the high blood pressure  

the belly fat the cardiovascular risk etc at 72  hours things really start kicking in and we see  

deeper levels of autophagy which means more  cleanup of these things we talked about the debris  

and the waste the misfolded proteins and other  low-quality parts so the body gets really really  

picky because it says you know i really need some  resources i need to build this thing over here  

and this thing wasn't perfect so let's disassemble  that and and rebuild it but here's what  

really starts to kick in that's interesting  at 72 hours and big words hematopoietic  

stem cell regeneration and rejuvenation so heme  has to do with blood and poisons poetic has to  

do with building with making and stem cells  are the cells that are the originator cells  

the cells that become other things so it's like  the baby cells that we use to make other cells  

and therefore this process in other words  is a form of rejuvenation it's rejuvenation  

of the tissues and when we're building the new  tissues it's like a younger quality to it so  

this is pretty profound this is about the white  blood cells which is our immune cells and they  

have found that if you do repeated fasting not all  the time but at certain intervals of 72 hours now  

you get some protection against chemotherapy  so chemotherapy is like an evil fight to fight  

an evil it's a poison and you're giving it  to the body in the hope that it will poison  

the cancer cells more then it will poison the  body cells but it is a burden it's a severe burden  

and therefore it has a tendency to suppress the  body's stem cells and the body's immune system and  

the generation of these white blood cells but what  they have found is that if you do this fasting you  

can offset the damaging effects of chemotherapy so  the people who fast while they're doing chemo they  

maintain their immune system at much higher  levels if we keep going to 120 hours or five days  

then there is nothing dramatically new that's  happening but we are increasing the degree of  

everything that we talked about before it either  stabilizes or builds to higher levels and more  

than that it gives us more time and we have more  time for fat burning if your goal is weight loss  

we have more time for clean up and repair if you  are interested in autophagy and reversing disease  

and we have more time to turn around momentum  so think about all of these disease processes  

and all your metabolic pathways as having  momentum and if you go a little bit longer  

now you have higher degrees of turn around  but you also allow more time so it's sort of  

like a super tanker you can't turn it right away  but if you're patient it will happen over time  

and with this you're also allowing the cells to  forget their old set points so again with these  

tendencies we have in the body the body develops  set points there are set points for all sorts of  

different things including your body weight so if  you have a tendency to bounce back then this can  

help in setting a new set point forgetting the  old set point and finally creating a new one i  

often get asked when does it start and people want  a specific timeline like yes but just tell me the  

answer tell me when it begins and it doesn't work  like that so i created this to sort of try to give  

you an idea that everything is always there to  some degree but it either increases or decreases  

so glucose for example is going to slowly decrease  over several days until it stabilizes because  

glucose is something we have to have blood glucose  it will never go away same thing with insulin  

it will always be needed when you don't eat  you're allowing more time for it to decrease  

but we are going to have a baseline level  that's going to be necessary at all times  

growth hormone is going to have a low baseline  level but it's going to increase so by time we  

hit 48 hours we'll have 500 percent more growth  hormone and then it will probably slowly increase  

but not in definitely it'll hit a plateau and sort  of stabilize at that level ketones and autophagy  

these are things that they're not absolute zeros  but they're virtually zero they're virtually  

non-existent before 12 hours and then they barely  start and then they get some momentum around the  

18 hour mark now take a look at this a lot of  people most people who eat three or more meals  

are never going to get past 12 hours of fasting  so they never will change their baseline markers  

they'll never experience autophagy or any  significant ketones but if you just get to  

18 hours something as simple as skipping  breakfast and having an earlier dinner now  

you're seeing more growth hormone you're seeing  some ketones and you're even seeing some autophagy  

kick in at 24 hours we're doing the same thing  we're seeing increases in all of those and if we  

can keep going until 48 hours now we're seeing  dramatic increases in these like we said with  

growth hormone we're up five-fold then if we can  go one more day to 72 hours now we're seeing most  

of the changes that we're looking for if we're  trying to reverse a disease or start affecting  

stem cells and things like that now here are  the ranges i think would apply to most people  

it is from 18 to 48 hours and then the 72 hours so  if you have reached most of your weight and health  

goals you can absolutely make 18 hour fasting  a lifestyle that's what i do most of the time  

not because I'm trying to control anything but  because it is just so convenient i eat twice a  

day six to eight hours apart usually and a two  big rich satisfying meals and outside of that i  

have no hunger no cravings no unstable blood sugar  nothing like that a lot of people can do that and  

lose the weight but if you're not losing weight  or not reducing insulin with that then you can do  

one meal a day if you have really stubborn  weight you can go to one meal every other day  

and that is actually quite sustainable that  you can do that for as long as you need to  

to reach your weight goals you could not  eat on Monday Wednesday Friday for example  

and if you need to do that for six months or 12  months or 18 months to get where you want to go  

then that's absolutely sustainable and then  once you have reached your goals you're  

off your diabetes medication you're at a more  normal weight now you can move back in and  

start experimenting with 24 or 18 or 16 hour  fasts the 72 hour where does that come in well  

that's a great tool to do once in a while even  if you're healthy if you've reached your goals  

it's a great tool for maintenance for disease  prevention now you do a three four five day fast  

once a year twice a year or maybe even three or  four times if you feel up to it but you don't  

have to do it that often however if you have again  trying to work on something pretty intensely like  

severe insulin resistance or stubborn weight you  could do a 72-hour fast every couple of weeks  

that wouldn't be a problem and where it really  comes into play is if you're trying to reverse  

a severe condition if you have a cancer or if  you're working like we said on chemotherapy now  

you do that as often as you need to as often  as you can but again you have to balance it  

against getting enough nutrients if you enjoy  this video you're going to love that one and if  

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