The 5 Physiological Stages of Fasting: Explained by Dr. Jason Fung

Dr Jason Fung ,nephrologist and best-selling

author shares his experiences utilizing an

individualized approach to fasting

to successfully treat thousands of

overweight metabolically ill and

diabetic patients

and why being a doctor who specializes

in kidney disease

gives him a unique insight into early

indications of metabolic disease

let’s listen to Dr Jason Fung.

Dr. Jason Fung’s Eating/Fasting Schedule

I don’t eat breakfast a lot of the days

of the week so

when i have something at lunchtime then

i’ll often just kind of just keep

working and

once you get used to it it’s really not

very difficult because your body will


take the calories it needs from your

stores of energy which is your body fat

and the glycogen which is stored away

so it’s a completely natural process and

when there’s time then i go and eat and

it makes it so much easier you don’t

have to obsess all the time about

oh i don’t have time what can i eat and

then you wind up going to

the local donut store and then oh

there’s just muffins so then you

reference and you know that that’s not

good for you but then you feel this


to eat there’s all this pressure on

people oh you’re not

hungry but you must eat it’s like well

eating when you’re not hungry is not a great

weight loss strategy if you look at the

what happens when you wake up it’s very

interesting because there is a counter regulatory surge which happens

just before you wake up so somewhere

around 4.30 a.m your body releases

certain hormones which are counter

regulatory hormones

that is they run counter to insulin so

these are the sympathetic nervous system

gets activated growth hormone

noradrenaline for example so these all

spike just before you wake up and the whole

point of it is that they are actually activating your body

for the day ahead and one of the things that these counter

regular hormone counter regulatory hormones do

is they stimulate your liver to pump out some glucose so in fact

you don’t have to eat to get ready for the day

your body’s already done that for you. If

you start to eat well that’s fine if you

like to eat breakfast it’s fine but you


have to, then you don’t. 

Lots of different cultures have

done all kinds of different eating

regimens throughout history

and people have done well on all

different ones so early. Simply

if you look at for example circadian

rhythm of hunger i actually think that’s

very interesting because if you

take people and simply measure their

hunger over 24 hours there is a

tendency to go in certain patterns and

the rhythm is that your hunger is

actually lowest at somewhere around 7 30 8

at 8 o’clock in the morning so again and

that’s because of the

counter regulatory surge and the fact is


the hormones is what determines your

hunger because 8 a.m

is usually the longest period before

you’ve eaten because you’ve often

not eaten all night so it may be 12 14

hours since you’ve eaten yet

your hunger is actually the lowest that

it is through the day

so again that’s why a lot of children

don’t feel like eating breakfast

and so on and the only reason they start

eating breakfast is that we force them

and we tell them

that you got to eat breakfast you got

eat breakfast garbage breakfast and it’s

okay if you want to eat breakfast but

what you want to avoid is eating all

this processed sort of highly refined foods

that are so convenient and have taken

over the breakfast aisle so to speak

because they’re so easy we can grab them

and go muffins and donuts and all these

pop-tarts all these sort of things that

are super unhealthy for us

because we don’t want to cook bacon and

eggs in the morning it’s like who’s got

time for that you gotta cook clean eat

all this sort of stuff

right so even if you look at the

circadian rhythm

if you’re again if you’re the least

hungry at 8am

why would you force yourself to eat it

doesn’t make any sense

it’s based on people who have

said that oh it’s going to keep you full

throughout the day it’s going to both

boost your metabolism

the data behind those claims is very

very sketchy. People get brow beaten into oh 

you must eat it, you must eat. It’s like, no

there’s lots of different options- you

can eat if you want and you can make it

work for you and 

if you’re really not hungry at breakfast

then you don’t want to eat and you’re

way too busy, you want to rush out the door to get to

work and get to school, yes you can

just skip it and go to lunch time, it’s


What’s interesting is the very word


“breakfast”- it’s the meal that breaks your

fast. It’s not the “oh you must eat as soon as

you wake up before your feet hit the

ground” sort of thing.

You can break your fast at any point, you

can break it at 8am, you could break it

at 11am, it makes no difference

and the other thing that’s very

interesting- a word is that

what it implies is that you actually

have to fast in order to be able to

break your fast

so what this tells us is that

it’s part of the natural cycle of life

you have to eat

but you have to fast fasting is merely

the absence of eating

so if you have a period of time that’s

when you eat and you have a period of

time where you should fast

right you don’t eat all the time that’s

not a good weight loss strategy either


we get told again and again oh

before your feet hit the hit the hit the

ground you got to start shoving food in

your mouth

and then oh you can’t you can’t you have

to eat all the way up until you go to


you know six or seven eight nine ten

meals in the day

oh that’s gonna make you healthy where

is your period of fat

so this was described by a lot of the

physiologists and

many of these studies are very old and

it basically

is a process of moving from

storage of food energy to burning food

energy so

what happens is that when you eat

insulin goes up and insulin is a hormone

it’s essentially a nutrient sensor so a

lot of things other than just

carbohydrates a lot of proteins for

example will also stimulate insulin

when you eat the insulin goes up and it

tells your body that you need to store

food energy because you’re eating and

you’ve got more food energy

than you actually need so some of it

goes to open up the cells to glucose for

example and that’s what we tend to think

about for insulin is that

it lets the cells use the glucose but

the other thing it does is it stops

lipolysis which is the burning of fat

and glycogenolysis which is the

storage so you store sugar

in the form of glycogen in the liver so

glycogen is long chains of glucose the


packages them all together and stores it

in the liver

and this is why you don’t die when you

go to sleep every single night is

because your body can store some of this

food energy

so when you’re not eating it will bring

it back out

plants for example will link all these

chains of glucose together is starches

so amylopectin for example there’s

amylopectin a b

and c so there’s different forms of

starches so for example

white bread white flour uses amylopectin

a and this is the wheat

that puts all this glucose together

so that’s what plants do they use starch

and humans use glycogen and lots of

mammals use glycogen as well

but essentially you can think of it as

stored sugar because that’s what it is


the body has two storage forms of energy

it can store glycogen

and when that’s full you can’t store any

more because the liver

simply can’t hold it so your body then

turns to storing fat and this is the

process of de novo lipogenesis

so de novo is a word from latin means

from new lipogenesis lipo means fat

genesis means the creation of so it’s


creation of new fat but it’s the

creation of new fat from carbohydrates

dietary fat doesn’t actually do this it

actually just gets absorbed directly and

goes into your fat cells

the excess carbohydrates if you take a

lot of carbohydrates

it gets turned into glycogen it gets


and then body fat so there are two


storage systems because they fulfill

different roles in the body

the glycogen is easily accessible that

is the body can kind of move in and out

of glycogen very easily

but there’s a limited amount body fat is


harder to get at but it has unlimited

storage so

the analogy i sometimes use is it’s kind

of like a refrigerator

and a basement freezer like a chest

freezer the refrigerator it’s right

there it’s easy to put food

in it’s easy to take food out but

once you’re full you’re full the freezer

in the basement

has unlimited capacity that is you can

put several freezers downstairs but it’s

harder to get to

and that’s how the body stores energy as

you stop to eat so

the process of fasting goes through

several phases so

when you eat insulin goes up you store

food energy in those various forms

you’ll notice of course that protein is

not stored as energy

if you eat a lot of protein then your

body uses some of that protein for

building building protein but the excess

actually just gets turned into glucose

because it can’t store

that excess protein so people who are

pounding back

it’s very hard from a dietary standpoint

to eat a high protein diet it tends to

be very unpalatable

yeah natural foods of course are good

but it tends to

when when you’re just eating there’s a

lot of fat in there as well

you just have those shakes and stuff

which is kind of pure protein it’s

it’s it’s not that it’s not that

effective it’s not as effective

as you think it would be but you got to

realize that the bodybuilders are

actually breaking down a lot of muscle

all the time because they’re working out

they’re breaking down the protein so

they they may require

more protein so the first phase the

first phase is the eating phase then you

start to go into

the fasting phase so from about zero to

sort of 24 hours

what happens is that your insulin starts

to fall

so the food that you eat is gone and now

you need to start pulling out energy so

you need to start pulling energy back

out from the body in order to

keep it working so the first place it

goes is the glycogen

so what you see is that your body

continues to burn

glucose up to about 24 hours

at about 24 hours the glycogen stores

run out

and there’s a period of gluconeogenesis

so gluconeogenesis

is again from the word gluco meaning

glucose neo which is new genesis

creation of so it’s the creation of new


it gets created from protein

so you will break down some protein

and create glucose in order to feed the


you’re ramping up fat oxidation at the

same time but that takes a little bit of

time because as i said the fat

stores are very large or can be very

large but they’re difficult to get at

so it takes a bit of time so in that 24

to 36 hours

you get this period where you’re

actually breaking down some protein

you’re still living off the rest of your


and then that’s it at after 36 hours

then you get

the kind of fat oxidation starts to take


so protein burning really drops to a

minimal sort of turnover

and then the breakdown and then you

start to see the fat oxidation so

fatty acid levels go up in the blood and

you see fat in the blood and basically

the body lives

off of stored fat from then on says just

physiologically what happens when you

stop eating there are ways to kind of

hack the system so to speak so ketogenic

diets for example

will use very very high fat diets

in order to reduce serum insulin because

insulin is a

one of the sort of master hormones that

controls where your energy

is coming or going so you have to

understand that insulin is essentially a

hormone that tells our body to store our

energy when insulin is low

your body wants to burn energy but you

can’t do both and this is

uh something that’s very interesting is


and it makes sense because if you’re

burning energy you don’t want to start

and vice versa so if insulin is high or

it’s low

the the effects are completely opposite

when you’re it’s and there’s something

called the Randle cycle in physiology as

well which is

that when your body is burning glucose

it’s not burning fat and when it’s

burning fat it doesn’t burn glucose

so they actually and this is a

a system that is designed because you

want to kind of use

one fuel or the other and not both at

the same time it’s not very efficient so

that’s why there’s this kind of

sequential move from

burning glucose at first and then fat

and that’s how you kind of hack the

system because if you have

super super super low carbohydrate


you essentially are just providing fat

to the body

obviously there’s some protein there but

mostly fat so

ketogenic diets for example are very

very high fat diets

and because it’s mostly fat your body

turns into burning fat which is why you


ketone production so ketones actually

the body does most of the body doesn’t

use ketones

the most of the body directly uses fatty


so the triglycerides so fat body fat is


it’s a glycerol backbone with three

fatty acid chains as you break those

fatty acid chains off

muscles will use fat directly the

glycerol gets turned into glucose

because certain tissues need glucose the

brain is one

but the brain uses way too much glucose

so in order to get

the fuel into the brain your body

produces ketones which can cross the

blood-brain barrier and

feed the brain and that reduces the

reliance on glucose

so that’s where ketosis is that’s where

ketogenic diets are

and that’s how people kind of uh kind of

gain the system to get where they’re


now there’s something called the glucose

ketone ratio

so different people actually are quite

different it’s interesting that as your

glucose falls

you expect your ketones to go up but

that’s not what happens in everybody so

some people actually don’t bring up

their ketones and that’s why some people

get this sort of keto flu or they don’t

feel so good when they’re not adapted to

that because their ketones don’t respond


most people will go back to it very

quickly but yeah

if you don’t eat that’s a very fast way

to get into ketosis

if you want for the for the large

majority of people the period

from kind of 24 to 36 hours roughly

where people

are burning protein that’s where people

get the misconception that oh you’re

going to lose muscle you’re going to

burn muscle you’re going to burn muscle

and that’s if you’re just to look at

that you might think that makes sense


what they miss is that when you start

refeeding when you

start eating again growth hormone levels

have gone way up so again remember that

growth hormone is one of the

counter-regulatory hormones

right so norepinephrine growth hormone

the sympathetic nervous system all go

up as your insulin goes down so growth

hormone is going up so when you actually

start to eat again

you are starting to rebuild all that


protein but it’s actually better because

what you’ve done

is when you break down those protein

your body actually identifies the kind

of old

junky sort of proteins that it doesn’t

need the cells that it doesn’t need and

gets rid of them

and then rebuilds new ones so it’s

actually a complete renovation

cycle as opposed to leaving that old

protein where it is because if you

continually eat all the time you don’t

have that breakdown that breakdown is

very important

in in medicine for example for new bone

you don’t simply have the bone just

sticking around there’s actually a

continual cycle of renewal of breakdown

and regeneration breakdown and

regeneration and this is

what the fasting does it gives you that

period of breakdown

and regeneration so if you look at


of alternate daily fasting for example

they’ve done studies where they’ve

compared calorie restriction with

alternate daily fasting

over a period of 32 weeks they’ve

measured lean mass at the end of it

in fact the calorie restriction

people their lean mass percentage went

up by 0.5 percent

because they had lost some weight but

the alternate daily fasting room went up

by 2.2

so in other words the fasting group was

four times

better at preserving lean mass which is


contrary absolutely and it’s directly

contrary this is what’s very interesting

because you have studies of

people who are growth hormone deficient

for example older men some people when


measure growth hormone and they’re

deficient then when they replace them

they see this

increase in lean mass increase in bone

mass and all these sort of

really beneficial uh things so

i think that that’s what people miss

when they just look at that

period of gluconeogenesis when it’s

breaking down that they miss that

that period where you’re rebuilding just

like if you’re to do a renovation

you have to tear stuff down first you

have to take down uh all the old

cabinets before you put up new cabinets

so if you just look at the teardown you

say oh you’re

that’s terrible but you haven’t looked

at the full cycle of

feast and fast is much more powerful

growth hormone is a

counter regulator hormone so as you eat

insulin goes up so growth hormone goes


nothing shuts down growth hormone

secretion like eating

it’s fascinating when they do these long

fast five days and so on

the growth hormone levels just go way

way up

when you see the pattern of

growth hormone secretion get this big

spike in the

beginning of the day that during that

period of

longer fasting that most people have

that 12 to 14 hours where you don’t eat

once you start to fast where you just

don’t eat anything at all

you start to see little spikes of growth

hormone all

all throughout the day so your body’s

actually trying to build and repair and

so on

obviously if you fast forever you’ll die


assuming that you eventually eat again

and provide the nutrients that are

needed your body

actually goes into that an anabolic mode


it is fascinating and i wouldn’t have

i wouldn’t have thought of it logically

either but this is this is physiology

this is what happens we know

that nothing turns off growth hormone

like eating fasting provides

sort of a lot of different hormonal


there’s changes in obviously insulin and

norepinephrine and growth hormone

sympathetic nervous activation this is

one of the other things that people

don’t necessarily understand is that

if you think about what these hormones


they actually activate the body so


nervous system is the so-called

fight-or-flight response

so the body’s actually getting activated

during this period of not eating

norepinephrine or adrenaline which is


is is pumping up your body it’s not it’s

not shutting it down and this is what

they say oh you don’t eat you’re going

to go into starvation mode your

basal metabolic rate will go down it’s

the complete opposite

when they say you’ll go into starvation

mode they’re actually not just wrong

they’re like 100

wrong because it actually activates so

people come back from

fast and they go whoa i cannot believe

how much energy i

had so yeah because your body is pumping

you full of energy

and if you think about it from an

evolutionary standpoint for example it

makes total sense if you are a hunter

and a caveman

and you don’t eat for a couple of days

and your body starts to shut down

you will never eat again you have no

energy to go out and hunt you have no

energy to catch those rabbits whatever

so your body is simply not that stupid

what it does is it switches energy

sources so it says okay

there’s no more sugar i can’t burn any

sugar i’ve run through my glycogen

i need to switch to body fat not only am

i going to switch to body fat but i need


pump you up so that you can go out and

hunt some woolly mammoth

otherwise i’m going to die so that’s

what it does so it it actually burns fat

pumps you up gives you more energy and

it’s like wow that’s

exactly what you want to do because

the the alternative is is is not viable


these are physiologic responses these

are is not just kind of hocus pocus you

can measure these hormones and

you know what noradrenaline does it

pumps you up when you measure people

after prolonged fasting their basal

metabolic rate goes

up so for example a study i

i cited which measured metabolic rate

after four days of fasting

shows that when you measure the resting


expenditure at the beginning and the end

of the fast

it’s about 10 higher at the end of those

four days

so your body’s not shutting down it’s

actually being pumped

up so all this stuff about oh you should

never skip

this meal because you’re gonna go into

starvation mode

they’re completely wrong because your

body is pumping

up not not shutting down in fact if you

do calorie restriction we know from

study after study all those studies on

the biggest loser for example

that if you simply try to reduce a few

calories per day so if you say oh i’m

gonna go from 2000 calories to

1600 calories per day we know that your

energy expenditure is going to go from

2000 down to 1600

you will for sure go into so-called

starvation mode by but

it’s the calorie restriction that does

that why because your body

remember has two sources of energy it

has food and it has stored food

or body fat so if you keep eating

insulin is high your body says i need to

store energy

but you only have sixteen hundred

calories your body wants to burn two

thousand but it’s only getting sixteen


your insulin is high so you can’t store

energy and burn energy so you can’t

so insulin is high so your your fat

stores are locked away

you can’t access those because you’re

still eating all the time

right and what it does is simply i’m

getting 600 calories in

i’m gonna reduce my expenditure to

sixteen hundred so you’ve gone down

the difference when you go down to zero

when you’re it’s it’s about moving that

insulin way down

is that all of a sudden you’ve unlocked

all those stores of fat

the studies show is that almost all

these attempts to

simply restrict your calories now

insulin will go down because

insulin goes down whenever you eat

anything assuming your diet doesn’t

change much but you eat a little less

your insulin will go down slightly

but it’s not going down to like zero low

carbohydrate ketogenic diets do a pretty

good job

also of bringing that insulin level down

and actually you can lower the insulin


even with a high carbohydrate diet it’s

just that it’s not

sugar and refined grains gotcha there’s

lots of ways

beans for there’s a huge difference

between beans for example and white


so they may be the same number of grams

of carbohydrate

but the insulin effect the glucose

effect is

hugely different and you see that on the

glycemic index

so therefore if you look at some

traditional societies for example they

ate a very high carbohydrate diet but

their insulin levels were not bad. The

key, of course, is that they’re not eating

sugar they’re not eating

refined grains and they’re not eating

all the time so

when you do that you can tolerate these

carbohydrate foods

so natural carbohydrate containing foods


sort of things don’t have nearly the

insulin effect as

our sort of refined highly processed

foods that we kind of eat in

modern day North America

so the biggest loser diet is really the


standard sort of eat less move more

advice that

physicians and dietitians have given

but it’s sort of that eat less move more

on steroids it’s

eat a lot less and move a lot more so


calorie restriction goes down to about

say 1200 calories something like that

they don’t want to be accused of

starving their patients which i think is

ironic because i think if they went to

zero they have done a lot better

and their exercise goes way up because

on the show you see them

exercising and throwing up and all this

kind of stuff

so it’s essentially the same advice that


give eat less move more but kind of

jumbo size and what they show is that

their metabolic rate just plummets

so they go from as they lose weight

which they do in the short term their

metabolic rate also drops

and because their metabolic rate drops

they’re feeling

more tired and cold more hungry

and the worst part is that because

they’re burning less calories

even as they’re eating less calories

their weight loss slows eventually


so now your weight is not dropping but

you’re burning 1200 calories instead of

two thousand so

your liver doesn’t get enough uh energy

or your heart gets less energy you’re

you’re not um you’re not generating body

heat you

feel really crappy and your weight is

still down so

as you relax that you start eating say

1400 calories

yeah but you’re only burning 1200 so

that weight comes right back so you see

on that

on that six-year study that some people

wound up like 50 pounds heavier than

I think it’s about controlling insulin

not about controlling calories so you

can do it many different

ways there’s uh paleo diets and so on

intermittent fasting just happens to be

one of the

better studied ways to maintain

your basal metabolic rate so we know

from our studies from

physiology studies that this is what

happens so why don’t we

use our knowledge to to

tweak it i mean i don’t say that

everybody needs to fast or should fast

it’s not easy it’s not

fun but why don’t we let people

use it as an option it’s it’s if you

don’t eat you’re gonna lose weight

that’s not that hard to understand what

you have to understand

too is that this is completely natural

and as physicians

physique when i talk to physicians

physicians always understand this point

because i say to them well we tell

people that they should never

ever miss a meal if you miss a meal

you’re gonna die

but we tell people to miss meals all the


when they have surgery you have to fast

when you do a colonoscopy you have to


when you do fasting blood work you have

to fast when you do an ultrasound you

have to fast so there’s all these


where we actually tell people too fast

and guess what nothing bad happens

everybody’s normal they might be hungry

they may be a little cranky but that’s

about it

nothing bad happens so why can’t we

simply use that as a therapeutic tool

to make people lose weight because these

people have type 2 diabetes they’re

obese they’re

having heart attacks they’re having

strokes this is a serious problem to

leave them at that level

the standard advice to eat less and move

more doesn’t work we all know it and the

studies all show

that it doesn’t work so why shouldn’t we

use this

tool that we have which is honestly the

most powerful weight loss tool because

you cannot go lower than zero calories

you can’t get

negative calories yeah so therefore this

is the most powerful tool

and we’ve decided to not use it like are

you kidding

me that’s got to be the craziest thing

i’ve ever heard everybody assumes that

you can’t do it because hunger will just

build and build and build and then it’ll

be intolerable

but that’s not actually what happened so

you can look at

the so-called hunger hormone ghrelin and

if you take somebody and you fast them

you can measure their ghrelin levels and

see what happens

so they’re in normal people you get this

three sort of spikes at breakfast lunch

and dinner so clearly there’s some

element of learning involved because we

expect to eat it’s 12 o’clock we expect

to eat so

our body kind of preempts us and expects

it and

puts out ghrelin but what happens when

you don’t eat when you skip that meal

is that the ghrelin does not continue to

go up it just falls back towards


so that’s really interesting because

again when i speak to physicians

they all know this because we all during

a residency medical student days we

miss meals all the time we’re just way

too busy

and you don’t have 45 minutes to sit

down at the cafeteria so you skip lunch

and that’s it so you’re a bit hungry

during that hour

and then once it’s faded so at 12

o’clock to 1 o’clock you’re a little bit


but you’re so busy you just keep working

by two or three o’clock you’ve forgotten

that you didn’t eat

and then sometimes you go huh i wonder

if i ate today and you didn’t

because the ghrelin has gone completely

back to baseline

so over the day these hunger actually

comes in waves and when people know that

they can plan for that so i say well

you know it’s going to come prepare for

it keep yourself busy

have some tea have some coffee drink


and let that wave just ride over you let

it pass and then by two or three it’s


and basically what you’ve done is you’ve

let your body

eat lunch or dinner or whatever of your

own body fat

and that’s perfect that’s exactly what

we wanted to do

and when you look at multiple days of

fasting it’s even more interesting


after about day one day two the hunger

actually the ghrelin which is

the hunger hormone peaks and then starts

to go

down so this is exactly what we see in

our clinic so when we have people doing

longer fast five days seven days 14 days

everybody says wow how can you do that

and the secret is that after day two

the hunger slowly fades on day two

you’re like wow i will never get

through this seven day fast on day five

you’re like oh i can go on forever

the hunger has completely disappeared it

is because now your body

is just feeding you body fat constantly

the levels of body fat

the fatty acid levels are high so your

body’s like why do i need to eat i have

tons of fuel here

because you’ve shifted fuel sources so

again people always get the wrong idea

they think it’s a one compartment

problem where all the calories

goes in one box and all comes out of one

box it’s a two compartment problem

there’s the food

and there’s a stored food and what

you’ve done is you’ve shifted your

your your fuel to come out of the body


and now there’s just so much of it that

and it’s interesting because my

day five day six and not everybody but

some people go wow

i cannot believe how good i feel it’s

like their energy level is way up

because of the

adrenaline, the sympathetic nervous

system. I have no hunger at all

and a lot of people also note this sort

of mental clarity

which has been remarked over and over

again how they they think that they’re

much sharper more clear

and it’s like wow i feel amazing it’s

like well you know not everybody’s going

to be like that but if people

have this natural physiologic

response and they do well why don’t we

let them do it

and then they’ll lose weight because if

you don’t eat for seven days you will

lose weight

one other thing that’s that i would warn

people about though is

with about weight loss is that there’s a

lot of water loss

this is what people will tell you the

amount of weight loss the amount of fat


on a fasting is only average as

half a pound of fat per day because a

pound of fat is roughly 3 500 calories

so if you’re eating normally 1800 2 000


it’ll take two days to burn one pound of


so on a seven day fast which sounds

really extreme

you can expect to lose three and a half

pounds of fat

that’s it so if you have a hundred

pounds to lose and you say wow i’m

expecting the seven day fast to do a lot

you will

you know you have a hundred pounds to

lose and you lost three and a half

that’s it

you will lose more because the rest of

that is water so you’ll probably lose

seven pounds 10 pounds even but if you

lose 10 pounds

six and a half of that will come back so

that you’re only three and a half down

at the end of the seven days

and that’s where people say oh you

failed because look you lost all that

weight but seven pounds came back well

you should have expected that that seven


was going to come back so you should

never have expected that loss of

water as it comes back it’s not a

failure it’s basically to what to expect


having having the experience when people

understand this and expect it then they

don’t feel so bad when

this weight starts to go back up because

you know that that’s what’s supposed to


i’ve never done a very extended fast

because it simply doesn’t fit into my


very easily i have dinner with my family

most of the time so i do a lot of

shorter fast the 24 hour fast i have

done a few

i’ll tell you the reason i did them was

that i went on a cruise i gained a lot

of weight

because i wasn’t watching what i was

eating and i made a decision that i

wasn’t gonna watch what i eat so i ate

all kinds of crap like

ice cream and desserts and all that and

everybody knows so i gained a ton of

weight my rings weren’t fitting and it’s

not like okay this is not good

so then i went on a kind of longer fast

about i think

is about three days and i’ll tell you at

the end of the

it did three days then i went kind of

alternate daily fast and by the the the

next week

my weight was down to where it normally

was but i had a great time for that week


ate a lot of food that i don’t normally

eat and i think that

was probably the longest i did because i

was starting to get a little worried

with you know when the rings weren’t

fitting and my pants weren’t fitting

properly and so on

it was all the carbohydrates right i’m

not used to that high a carbohydrate

intake but

again that’s that’s as long as i’m gone

how long you have to go is unknown so

there isn’t

very much research into it if you talk

to some of the people who

have done these longer ones they’ll

often say

five days seven days i’m not sure i i

really don’t know

you can get a lot of the autophagy

cellular kind of what you want to do is

get into that kind of 24 36 hours where

you’re breaking down

protein because that’s where you’re kind

of getting that renewal cycle

pro the breakdown of the protein and

then the regrowth

you can get a lot of those benefits by

24,36 hours so i tend to do quite a few

of those

almost every day i come in and i see

somebody who’s completely off of their

diabetic medications and so on

one of the reasons we push some of the

longer fasts is that

these people are very sick that is we

can do this in a controlled manner that

is i can monitor them

as a doctor we have blood work we have

somebody that they can call

if they have problems we tell them to

stop so it’s a controlled situation

but the thing is that these are very

very high risk people

if you don’t do anything they will

develop a lot of different diseases

heart attacks strokes kidney disease eye

disease amputations all kinds of things


the rewards are much higher so we will

push the envelope a little bit more for


patients now you can also do very well

with shorter

intermittent fasting but it takes longer

it’s simply not as powerful as doing an

extended fast

yeah but again i would warn people that

it is something that

you have to adjust the medications

because you can’t take the same

dose of insulin for example and not eat

your blood sugar will

plummet and you have to do it in a safe

manner which we

try to do but yes you have to understand

that type 2 diabetes which is

sort of very near and dear to my heart

because that’s

the majority of patients that i treat

are type 2 diabetes

and what we see is that when you put

people on very low carbohydrate diets

when you use intermittent fasting you

can actually reverse the disease because

their blood sugars will come down you’ll

take them off all their medications

and that’s completely opposite to the

message that comes out from

the american diabetes association most

doctors which is that oh hey

type 2 diabetes is chronic and

progressive you’ve got it

you got it for life buddy that’s the

message that comes out

but it’s not true because we all know


as you lose weight that diabetes goes

away so you have to be able to make them

lose weight but instead of that the

doctors such as

what i used to do instead of really

working hard

to make them lose weight so that their

disease gets better

we would simply pump them full of

medications and i was guilty of that as

much as anybody else

but i understood eventually that these

people were not getting healthier

they were getting heart attacks they’re

getting strokes or getting kidney

disease which is where i come in

and they weren’t getting better yeah now

i see their diabetes kind of melting


again it’s it’s it’s not everybody not

everybody’s going to

do well with a fasting diet we’re all

individuals some people do very well


low carb diets some people sort of wild

diet or paleo diets

you got gotta find out what works for

you but what i what

my main message is is that these are

options for people don’t take away those

options of fasting intermittent fasting

extended fasting

because some people will do extremely

well on those other peoples will

they’ll do terribly and they’ll hate it

and i say well if you if it’s

not working and you hate it don’t do it

do something else

but for those people who do very well

well hey this is beautiful

yeah refeeding syndrome is actually

something slightly different so

during extended fast what you can

sometimes happen and this was described


in sort of extreme

prisoners of war in world war ii for


when you start to eat insulin 10 goes up

but because you’re very malnourished at

the beginning

phosphorus levels in the blood actually


so there are all the phosphorus is going

back into the cell due to the high

insulin load of the food and it gets so

low that you can get heart arrhythmias

and people have died for example

so if you look at the risk factors for

refeeding syndrome

it’s sort of more extended fasting five

days and beyond but also a baseline

level of malnutrition that is people who


truly starving holocaust victims

uh prisoners of war that sort of thing

key is to

that people who are not in that sort of

malnourished state or at

fairly low risk of that so again these

are people who would be

for example six feet tall and 90 pounds

like they’re so skinny these prisoners

of war

yeah when you apply it to people on what


applied to they’re 200 200 300 pounds

the risk is very very low but you have

to be aware that that is a potential

risk and it’s out there

the key is to and from when they’ve

treated them in the past

as i said i’ve treated over a thousand

patients i’ve never seen it but then i’m

not treating 90 pound people i’m


390 pound people so the risk is highly

different but

you want to break the fast very slowly

so that insulin doesn’t go up you want

to try to avoid refined grains and sugar

when you’re refeeding you want to go

with more things such as

proteins and so on stuff with phosphorus


meat and so on you want to take it

slowly so that it doesn’t just

shoot up and in terms of the uh

the phenomenon where people say their

stomach shrank

it’s hard to know what that is maybe

it’s the ghrelin which has gone down but

we’ve all done this where we’ve gone

through a sort of extended fast and go

oh i’m gonna eat a lot

and then you eat a lot and you have this

big stomach ache

and everybody’s gotten that and

everybody who does fascinates like

you’ve all gone that and quickly teaches


not to do it because your body is

actually saying no

you don’t need this i’ve been feeding on

my own fat slow down don’t take so much

because i don’t want to switch back so

quickly to all this stuff so it’s very

interesting because a lot of people will

notice like yeah i’m so hungry

after my 36 hour fast but then i eat a

little bit i’m completely when you look

at these people who do hunger strikes

and all this sort of stuff

everybody kind of says wow how can you

do that and again remember once you get

past day two

every day after that gets easier and

easier because you’re actually just

feeding yourself body fat

if you look at 382 days

half a pound per day half a pound of

body fat per day is

somewhere just less than 200 pounds 190

pounds which is approximately what he

lost so if you’re

looking to lose 180 pounds and

unfortunately there are people who need

to lose that much that’s

the magnitude of the sort of caloric

restriction that we’re talking about you

could go down to zero for that amount of


so it’s funny because that’s the world

record it was monitored by physicians

they wrote it up

and so on and it’s like from okay

people can survive for 382 days

and we won’t even let people go 24 hours

without eating

before somebody starts brow beating them


stuffing a muffin into their mouth it’s

hilarious it’s like

are you kidding me one other thing i

would just say in terms of

when you’re getting into it there is a

period of adaptation

where about two weeks three weeks when

you start fasting where there are lots

of issues that come up

it’s kind of like exercise if you have

never run in your life and then you ran

and then your muscles are

all sore you’d be like oh running’s the

stupidest thing i’ve ever done

but you have to give it time you have to

get your body used to it so your body’s

not used to the fasting it’s not used to

shifting over to fat oxidation

so it’s kind of rusty and it’s not

getting there so you may get this kind

of keto flu where you’re just

kind of you’re not you’re quite yourself

you get a bit of brain fog you get a bit

of this get a bit of that

and what you have to understand is that

that happens to a lot of people

and the key is just to kind of keep

doing it keep letting your body get used

to it

and then after about two weeks three

weeks four weeks you’ll find that it’s

like nothing at all yeah

then now for example i can fast 24 or 30

hours without noticing much at all

half the time when i’m really busy like

writing the book for example i’m like oh

i do tons and tons of fasting not

because i really want to lose weight but

because i just want that extra half an


to do my work so then there’s all these

different benefits that come into play

when you’re fasting such as

having extra time and so on and that’s

terrific it’s such a good option for


it’s not a cure-all it’s not a you know

one of these miracle things but at the

same time you’ve got to realize it’s not

like the

latest and greatest fad

oldest dietary intervention in the book

there’s no intervention more like more


don’t eat for a while that’s what uh

that’s what dogs do

they get sick they stop eating.

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