The Fed and the Fasted State

In order to understand how the body gains and loses weight, you must understand how it uses energy. The body really only exists in one of two states – the fed and the fasted state. When we eat, the hormone insulin goes up and insulin is released. Now all foods stimulate different amounts of insulin release but few foods except for pure fat cause no insulin release at all. Insulin is really a type of nutrient sensor. It senses the ingestion of both carbohydrate and protein containing foods. Refined foods, particularly carbohydrates cause the highest release of insulin.

Our bodies need a continual source of energy for basic metabolic housekeeping – keeping the heart pumping blood, the liver and kidney detoxifying, the lungs sucking air, brain function etc. Obviously we need a source of energy for all that work and it must be continuously available. Since we do not eat food all the time, we have a system of storing food energy (in the liver and as body fat) for times where we are not eating.

The main mistake people make is believing that weight loss is a simple one compartment problem. That is, people think that all calories go into a single compartment and taken out of that same one.

Consider the energy balance equation: Fat = (Calories In) – (Calories Out). This is always true. Suppose that your weight is stable and you eat 2000 calories and burn 2000. What if you want to lose weight? You hope that you reduce dietary calories to 1500, and body fat will provide the other 500. Over time you lose body fat. That’s exactly what does not happen.

There are really two different places where our body can obtain energy

  1. food
  2. Stored food energy (glycogen in liver, or body fat)

But here’s the CRITICAL point. You can only get energy from one or the other, but not both at the same time.

Imagine a railroad track. Suppose you need 2000 calories to keep basic metabolic function normal. There are two different tracks where energy can come from – either food or stored food. You may only obtain energy from one source at a time. If you take energy from the first track, you cannot get any from the second and vice versa.

In the fed state, when you are eating, insulin levels are high. During that time, it makes sense to derive your energy from the food that you are eating. So what happens is that we shut down burning of stored food energy in the form of fat and glycogen. For all you technically inclined people, we say that insulin inhibits lipolysis and gluconeogenesis. This is a well known physiologic fact.

Throughout most of the day, assuming you eat 3 meals a day, this is the normal state of affairs. But what happens when you go to sleep? Because you are not eating, you are fasting. Insulin levels fall. You now need to pull some of the food energy you’ve stored away to keep your vital organs running. This is the reason you do not die in your sleep every single night.

As you fast, insulin levels fall. This is the signal to switch energy sources from food to stored food. You pull stored energy out from the liver (glycogen) and if that is not enough, body fat. Technically speaking, we say that we start glycogenolysis, gluconeogenesis and lipolysis when insulin levels fall.

If you fast for 24 hours, for example, what happens is that your body wants 2000 calories for that day’s energy bill. Since you are carrying around plenty of body fat, it’s no problem to supply that 2000 calories. Approximately 1/2 pound of fat will supply that easily and the body says “Whoa, I have tons of fat, take all you want’.  It is important to realize that this is a completely natural process. Humans have evolved this mechanism of food storage, and there is nothing inherently unhealthy about fasting. It’s all part of a natural balance of being in the fed state and the fasted state.

Another way to put it is that this. You either burn fat or store it. You can’t do both at the same time. The body is just not that stupid. If food is plentiful, you store food energy. If food is scarce, you burn food energy (body fat). The key hormonal regulator here is insulin. The change in insulin levels is what signals our body to go into fat storing mode or fat burning mode.

So what happens now if you are trying to lose weight by adopting conventional advice to reduce the dietary fat and calories, and eat 6 times a day. By doing so, you keep insulin levels high because you are eating lots of low fat bread, pasta and rice and eating all the time. This also happens in type 2 diabetes, where insulin resistance causes insulin levels to stay elevated.

Since insulin is high, you must get your energy from food, and cannot get any from your body fat stores. You reduce your calorie intake from 2000 calories to 1500 and hope against hope that you will lose weight. You do, at first, but then your body must adjust. Since you cannot get at your fat stores, if you are only getting 1500 calories in, you must reduce you calorie expenditure to 1500 as well.

So, you feel tired, hungry, cold because your body’s metabolism is starting to shut down. But the worst part? You don’t lose any more weight! Your weight loss starts to plateau, but you feel like crap. Over time, you start to regain some of that weight. So you decide that you’ve had enough and increase your caloric intake to 1700 – still lower than when you started. But, because you are taking in 1700 calories but only burning 1500 calories, your weight quickly goes back to what it was before you started the diet. Sound familiar to anybody?

The key to successful long term weight loss is not reducing calories. It’s reducing insulin. Because insulin is the switch that decides whether your body is burning food energy or stored food energy (body fat). If you are burning food, then you are not burning fat. It’s as simple as that. The key to accessing your body fat stores is to reduce insulin. You must let your body go into the ‘fasted’ state.

2017-10-12T20:15:34+00:00 118 Comments

About the Author:

Dr. Fung is a Toronto based kidney specialist, having graduated from the University of Toronto and finishing his medical specialty at the University of California, Los Angeles in 2001. He is the author of the bestsellers ‘The Obesity Code’ and ‘The Complete Guide to Fasting’. He has pioneered the use of therapeutic fasting for weight loss and type 2 diabetes reversal in his IDM clinic.

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JohnD
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Excellent post! It keeps getting clearer and clearer in my head : ) Soo possibly stating the obvious: First eating lots of fat keeps insulin low. Then, can the body tell the difference between ingested fat and body fat? Meaning that eating a high fat diet isn’t really that much different from fasting. The only thing to deal with in this scenario is ingested protein. but maybe as long as glucogenosis is low you’re still OK to burn body fat. Then there’s that last bit to make sure you don’t eat too much fat to enable taping into the reserves.… Read more »
Tommy None
Guest

Brilliant breakdown!

Sascha
Guest

Eating lots of fat will not keep your insulin low, it will at most turn a short high spike into a long medium spike, which arguably might be even worse. You have to cut carbs to get into ketosis, but to then burn your body fat you also have to cut fats. Dont fall into the high-fat low protein trap, nobody there has any abs to show.

Jacki
Guest

Thank you. This is where I may have been going wrong should the protein be high then ?

Kena
Guest
look, hight fat diet doesn’t mean adding fat to everything. simply eat high fat foods , vegan or not, like avocado, meat (grassfed if you can) , coconut/almond milk instead of normal milk, non starchy veggies, and, like dr. jason explained in his book The obesity code, yes you can live without carbs but there are proof and he wrote it for us, that eating whole carbs and fasting provides an amazing healthy life. stick to a no carb diet and enjoy life if you can, unless you’re an expert in making keto desserts with coconut/almond flour, and their milks,… Read more »
lass lassiter
Guest

Don’t over complicate this…Eat meat!

Dan
Guest

If you eat a fat-rich meal, and hence produce little insulin, then you will presumably still utilise the digested dietary fat as a direct energy source. That’s the fed state but in the absence of insulin. So the key to successful long term weight loss is not reducing calories … it’s a combination of remaining in the fasted state for longer while also reducing insulin levels while int he fed state. Correct?

Rese Plante
Guest

This is what I also understand, very well said, thank you.

Sascha
Guest

When you are in ketosis, cutting calories and lengthening the fasted state are the same.

Woot
Guest

Not exactly. Even after eating a ketogenic diet for some time, when I ate at a large calorie deficit for a prolonged time, my weight loss tapered off and I had symptoms of metabolism falling. It’s what brought me to Dr Fung. I did experience keto assisted fasting by keeping my blood sugar more stable into the fast and helping me feel less hungry – my body didn’t have to keep making that painful switch in and out of ketosis. But cutting calories in keto like a regular diet doesn’t work well – at least, it didn’t for me.

Orvan Taurus
Guest

The other thing from this is, “If not hungry, don’t eat.” thus extending the fast and maximizing use or stored reserves. Eat by the stomach, not the clock.

Mike
Guest
Well then, I would probably never eat cause I fasted without food ( only water ) for 9 days and didnt feel hunger at all during those days. Before that fast I used overeat because of strong food cravings (not hunger), but now I am still not hungry and have lost all food cravings. That fast changed my life to the better in so many ways. Now I basically dont eat for 16-18 hours and then eat during the 6-8 hours left. I must have reached balance and I am really losing fat now too, very quickly. I also try… Read more »
Achhantei
Guest

Hi Mile, I have just started the switch to intermittent fasting after coming across Dr. Fung’s talks. Still doing my R&D and wanted to ask what you ate (broadly) in those 6-8 hours? Did you fast for weight loss or other reasons? Would really appreciate your help. Thanks

New to fasting
Guest

No where in the whole website does it mention how often should a person undertake fasting.

Is it once a week?
Is it 4 times a month?
or Continue twice a week fasting till you hit the desired weight loss number??

I guess it be very beneficial if Dr.Fung could answer this.

Maya Aggani
Guest

Dr Jason Fung has two books, i.e., the Obesity Code and the Complete Guide to Fasting. I strongly recommend these books if you are new to fasting. Regards

Patrick
Guest

He wrote a book about fasting. He only reccommends long fasts (7-14 days) every 6 weeks I think. It could be longer, he recommends to be under medical supervision while attempting one of these longer fasts. You could simply do alternate day fasting. You eat every other day. There’s no set rules for fasting. Main thing is when you fast, fast. When you eat, eat! Don’t restrict calories on eating days, that could cause drop in metabolism.

JohnM
Guest
“Don’t restrict calories on eating days, that could cause drop in metabolism.” Metabolism will drop only if your body can’t readily access its fat reserves. Consider the two track metaphor above. When the fat track is blocked by insulin due to frequent/constant eating, the body’s only other alternative during a diet where you are using more calories that you are taking in, is to reduce energy expenditure – lower your metabolism. Feeling tired and cold are common symptoms. However, if the fat track is not blocked by insulin – even during a diet, you’ll easily switch to fat as an… Read more »
RahulPolX
Guest
Re: “Metabolism will drop only if your body can’t readily access its fat reserves.” @johnM There is this FastingTalk episode 20 “20: Problem With One Meal A Day, Nursing, Marathon, True Hunger, Pain Relief, Black Coffee” at 15m30s where Megan Ramos says that eating one meal a day WILL result in drop in metabolism, similar to Calorie Reduction As Primary. Apparently OTHER Fasting Regimens (such as 16/8, or EVEN multiday fasts) CAN also have this problem. I dont understand her explanation. Her explanation left even the other host Jimmy Moore in confusion. In the “Fasting Regimens” blogpost, Dr Fung says… Read more »
JohnM
Guest
Her explanation is that constant variation – unpredictability – is critical to preventing the body from establishing an automatic response to a given stimulus. This makes sense for example when considering that muscles strengthen and increase endurance to meet a particular demand. Once there they don’t change further. They will however continue to adapt if the sequence or timing of a given set of exercises is changed. With OMAD as an example, the implication is that one’s metabolism learns to expect and reduce energy output during the unfed part of the day and to expect a single meal at a… Read more »
Srinath
Guest

I believe Meagan Ramos meant that with OMAD you shouldn’t eat just 800 calories. Go the whole hog. Max out your daily need. Or get close to it.

Walt
Guest

Further, Dr Fung has a whole series of YouTube vids. There is a six part series that, pretty much, mirrors Obesity Code, if saving $12 is a consideration. I think it’s called “The Etiology of Obesity”…something like that.

Hansi
Guest
https://www.dietdoctor.com/intermittent-fasting/questions-and-answers Q: I try to combine 24 hours of fasting with longer periods. 3 days fasts every 2 weeks or 7 day fasts every third week or so. It is very flexible. I feel good during fasts as well. I manage to work, go every day by bicycle and even do my exercise 2-3 times/weak at the gym ( not very regularly). Have no medications or problems with my health either. Do you have any contra-indications on how often I should fast? Have read about fasts on your blog and even listened to your wonderful lectures on you tube and… Read more »
Walt
Guest
Every other day, eat a low carb, moderate protein, higher fat diet. On the intervening days either don’t eat at all, just drink water or eat a light supper. Additionally, buy the two books. I should point out a study done a year or so ago found that of all the diets, Atkins was best at initial weight loss and Weight Watchers was best at weight maintenance. Where I appear below to take issue with Dr Fung’s thesis, as it relates to insulin’s culpability, I am perfectly willing to accept that. Perhaps, in my case, I did not have an… Read more »
Jacki
Guest

So Sasha says don’t eat high fat and you seem to be saying do eat high fat. I’m confused a bit. Is there an optimum or minimum/maximum fat that DrFung suggests. I’ve just started fasting and doing 22-24 hr fasts 4 days a week or so.

Andre
Guest
Dr. Fung states that he fasts 3 times a week to maintain his weight. He fasts for 23 hours and then has one single meal. I think he is very reasonable since he is already fit. However, for those who have loads of body fat to burn, I strongly belive he recommends fasting every day. At least that’s what I do. I fast every day for 23 hours, and eat normally during 1 hour windows until I’m fully satisfied. I belive that he prescribes longer fasting periods for some of his patients, but from what he says he normally recommends… Read more »
George
Guest

Just a thought; is it possible to trick the body to burn stored fat by medically reducing insulin?

donny
Guest

Dr. Lustig mentions this in some of his lectures, in obese children that oversecrete insulin, drugs that reduce insulin do result in weight loss.

wang tao
Guest

The theory is seem to make sense, but the truth is that bodybuilders are eat all over the day, there is no fasting, but at their game time is very low body fat levels. Dr. Feng, how to explain it?

Doug
Guest

Hi wang tao. Bodybuilders commonly consume more calories than they burn, as they are trying to increase muscle mass. In preparation for competition, during their “cutting phase,” they reduce their overall caloric intake – while still eating a high proportion of protein (the better to retain muscle tissue) – in order to lose body fat.

Ivan Kerr
Guest

Wang Tao, bodybuilders also consume a lot of human growth hormone and steroids that help them gain muscle and burn calories. All of those drugs are bad for their health.

Patrick
Guest

Can’t you still burn body fat while not in ketosis? Will your body take from both glycogen and body fat? There are people who cut calories and they do lose weight, though in the long term they may gain it back. So are they insulin sensitive?

Walt
Guest
Patrick, I do not believe it is that simple. Ketosis is like 50 shades of gray. You can be slightly into ketosis which means you are burning fat. People who don’t eat at all for a week or two are deeper into ketosis, as would be shown on a keto stik. The whole, “though in the long term they gain it back”. That could be due to many reasons, principal among them is reverting to old diet. Yes, your body wants to restore its prior equilibrium, that doesn’t mean you have to let it. Eventually, it will accept the new… Read more »
John Brown
Guest

I like the fridge and freezer metaphor. And the coal-burning factory one. But I think of all the metaphors you’ve used to this point for explaining insulin’s role in switching between burning food in versus fat, this one is the clearest.

Walt
Guest

I concluded the coal burning factory is a false equivalency. For it to be an accurate analogy a CRaP diet would never work. Clearly that is 100% wrong. The body’s “prime directive” is “do not die”. It will in the absence of carbs, burn fat. In the absence of fat it will convert protein to carbs and burn those carbs.

Walt
Guest
“You hope that you reduce dietary calories to 1500, and body fat will provide the other 500. Over time you lose body fat. That’s exactly what does NOT happen.” Here is where I have a HUGE problem. If Dr Fung is even somewhat wrong on this what else is incorrect. Over the span of a year I lost 125lbs by simply a CRaP diet and going to the gym 6 days/wk. Specifically, dropping 1000cal off the est TEE and, for the most part that 1000 cal/day plus 3600 cal est burned at the gym per wk, I lost roughly 2… Read more »
Ryan
Guest

What kind of Diet are you following though? That also plays a huge role…CRaP is usually paired with the wrong Foods as well (Carbs).

The effect of eatin a High-Carb, Medium-Protein, Low-Fat diet is vastly different than Low-Carb, Medium-Protein, High-Fat.

If you’re otherwise healthy, why don’t you just try it out and see if it works for you or not?

Walt
Guest
Not exactly Ryan. CRaP, which I never like for it’s obvious implication, stands for Calorie Reduction as Primary. Elsewhere I did state my initial diet. A bowl of Raisin Bran w/skim milk for breakfast, a ham (or turkey) sandwich on whole wheat or rye with swiss cheese melted. yum yum, a whatever dinner 1/3 cup of rice perhaps, broccoli or brussel sprouts, steak or hamburg. Calorie count was for the day, depending on whether my TEE was 2800 or 1200 or, at the end, 800.There was no garbage. Now, after I discovered Fung’s videos, I cut out wheat, cut out… Read more »
Lori
Guest
If I may ask, how old are you Walt? If you are young or athletic, then most diets will work. I am in my 50s. When I was in my 20s and early 30s all diets worked for me. None permanently but I do not blame the diet. Now, this IF plus LCHF seems to be working ok. Nothing else was working. Prior to this when I was not out of control, I usually do a moderate carb, whole carbs only, no grains (I am wheat intolerant anyway, will eat bean pasta and so on) high fiber, with protein and… Read more »
Thomas
Guest
Dr Fung is actually 100% correct! If you are insulin resistant, THEN it is VERY difficult for your body to burn fat as the insulin keep the doors to your fat cells tightly closed. So, if you reduce your calorie intake from 2000 calories to 1500, and your body does NOT have access to your fat cells, (due to insulin resistance) your energy expenditure will get lower, your body will adjust and no fat burning will take place. Now add a fast!! Insulin will drop, the doors to your fat cells will open, and there you go:- YOU WILL BURN… Read more »
Walt
Guest
Let me say this again. The body’s prime directive (Star Trek) is “DO NOT DIE”. If Fung was 100% correct the people in concentration camps would all die at normal weight. For primitive man, food supplies didn’t turn off like a light, after harvest they weened down. Sure, by dead of winter perhaps they were exhausted but that’s why man put food up for the winter. Thomas, I don’t know how long you’ve been doing this but, I am telling you what happened. You are telling me what Fung says ought to happen. What you’re doing is called willful denial.… Read more »
R Reif
Guest
First, primitive man, the ones we’re referencing, *didn’t* harvest. Fung is talking about before ‘civilization” when humans were still nomadic. That’s why you don’t eat grains, that’s why fasting isn’t bad for you (primitive man went without for days on end while hunting/gathering) Second, I’m not sure of your point on concentration camps. I think Fung’s point is, those people should have died long before they did, based on static metabolic assumptions and calories/day in. Third, again, on the c-camp prisoners – wtf are you talking about? Those poor people burned through all their carbs, all their fat and most… Read more »
Christian
Guest

Why do you keep saying this, like we’re supposed to take your comments to heart? Haha. You’re not the doctor, Walt. Stay in your lane.

Doug
Guest
Hi Walt. Good discussion. One thing that makes sense to me is that with calorie restriction, the body may think that “lean times” are here, that starvation is a risk, and so it damps down the metabolism. With fasting, the body thinks, “Hey, we better go out and hunt, so we need to keep the metabolism and energy levels up.” Dr. Fung may have said this or the like – I don’t remember. That may be a rather romantic way to view things, especially if one if predisposed to think that total fasting is good. However, if the described mechanics… Read more »
Walt
Guest
“then it would explain why cutting out 500 calories, for example, won’t necessarily result in the 1 lb. per week weight loss that one might expect”. I must have read OC 4 times. I’d get towards the end and say, ‘wait a minute, he just contradicted himself or I missed something”. So next full read. So what I did Doug is got MyFitnessPal on my iPhone and tablet. Entered my weight, goal, activity level, and 2lbs/week. That dropped my estimated TEE by 1,000 cals/day. In addition to that I worked up to burning, allegedly, 600cal/trip to gym 6 days per… Read more »
Walt
Guest

As a quick addendum. In both books he clearly states, “All diets work and all diets fail”. That includes fasting protocols as well as he does say on fasting, you will reach plateaus. Again, I encourage everyone who hasn’t read the books to read the books.

Dr.Rob
Guest
You raise some good points Walt. I think main criticism to CrAP diet by Fung or me is that they imply, that all the foods are the same by that view point. It’s just calories! While on low carb, you definitely consume less calories, but it’s because you have no insulin and there is no hunger – calorie restriction happens naturally. But if you eat 1500 calories of sugar and high carb – then it’s scenario designed to fail, because there is still high insulin. You probably did reduce those things? Also increased protein and vegetables/salads? Insulin resistance also happens… Read more »
Martin Williams
Guest
Hello Walt. You quote some research into VLCD: Google Roy Taylor Newcastle magnetic imaging centre “Reversing the Irreversible”. His clinical trial subjects had an 8 wk, essentially, Slim fast diet plus a small salad, around 700cals/day. In 8 weeks they went from diabetic to fat free liver and pancreas and normal FBG and A1C. The science seems to be showing that if you reduce your calories to, say 1000-1800 per day you will cause your body to reduce its metabolism to compensate. But that going further, taking the daily calories to around 600-800 or less, produces a turnaround wherein meatabolism… Read more »
Walt
Guest
Hi Martin, I believe I’ve been mentioning Dr Taylor over the last several blog entries of Dr Fung. I, actually, discovered him and his research almost a year before I even knew who Dr Fung was. My dietitian told me at our first meeting I had a chronic incurable, progressive disease. I proved her wrong as I wanted to do my own research. Ironically, she wasn’t interested. I haven’t seen that evidence you mention on 600-800. I am not saying I question it, merely I haven’t seen it. This is why I think my hypothesis is so important. Get into… Read more »
Doug
Guest
Walt, I do agree that sometimes we see some overly-general comments, even from Dr. Fung. On the daily 500 calorie deficit and the presumption that this will result in a 1 lb. per week weight loss, perhaps it would be better said that “This does not happen for many people” (because of a slowing metabolism). The unqualified statement that it “does not happen” will indeed not be true for every given individual. Whether or not your metabolism slowed by a lesser calorie intake, I think your going to the gym 6 days a week took care of that and more.… Read more »
KML
Guest
Walt congratulations on your weight loss first of all. The biggest loser story that it tells perhaps brings up the biggest area of concern for you. All of these people gained the weight back. All of them. Once they stopped exercising excessively and went to the gym a normal amount their bodies just stopped. The gains they had were often even worse than their starting weights. Gaining weight is pretty demoralizing but I’ve have to say gaining, losing and gaining it back would the worst feeling of all. What you are doing may have some results over time but is… Read more »
R Reif
Guest

You said it yourself – you should have lost 154 pounds, not 125.

Obviously 125 is still terrific (Congratulations) but the point is you didn’t lose what you should have lost based on calories in and calories out.

Why?

I think Fung would say because your metabolism slowed down.

Woot
Guest
Hi Walt – I have also lost weight doing a terrible diet with calorie restriction + exercise. What happened is that I burned out on doing exhausted exercise all the time and having to count every single thing I ate. As soon as I slacked off, the weight rebounded hard. I didn’t even try for nearly 10 years because it seemed like such a battle for every ounce, and would so quickly come back. After keto + fasting, even when I recently stopped trying to lose weight for several months because of life events, my weight remained completely stable. That… Read more »
Walt
Guest
Woot, I believe people are reading into what Dr Fung says. I believe many people on here have never read his books so they just are true believers not based on facts but rather faith. I am not saying fasting doesn’t work, in fact Fung himself states and shows a 3 meal / day std diet, from up until late 70’s included 2 small and 1 large fasting period. People assume this is a zero sum thing that, for fasting to work, calorie reduction cannot. All I am saying, with examples, is that is untrue. Fung does not help matters… Read more »
Christopher Hamilton
Guest
Hi Walt, I have been in your position several times before. The first time I lost 100lbs through a crap diet I championed it too. But the benefit of hindsight is that I can speak from the “post loss” phase that you have yet to experience. What I experienced was a stubborn refusal of my body to burn that last few pounds, which I eventually resigned to live with. I threw out those old clothes and bought a new wardrobe two sizes smaller vowing to never go back. Problem was that my body had other ideas. It took some time… Read more »
Walt
Guest
“You must let your body go into the ‘fasted’ state.” Per graphic depictions in Obesity Code, Complete Guide to Fasting, and Dr Fung’s YouTube vids, you go into fasted state even when you sleep and between meals. He makes the point that the obesity and diabetes epidemic we’re in started late 70’s when we went from mom’s saying to snack it will ruin your dinner (3 meals/day) to breakfast-snack-lunch-snack-dinner-snack such that you essentially spent the day in a high insulin state storing more and more body fat, that the sleep cycle could not burn off so the net calories was… Read more »
Doug
Guest
Walt, you’re right that it’s a relative deal – that when sleeping or between meals we are “fasting.” I totally agree that for weight loss or weight stability we want the net calories to be less than zero or at zero. If a person feels good doing it that way – just eating less, then I’d say no problem. An otherwise healthy person at a desirable weight operates that way anyway – over time their caloric balance is right about zero, regardless of what they are eating, exactly. What I think makes the difference for some of us is that… Read more »
Walt
Guest
I don’t disagree with that Doug. However. With fasting, and he points this out in his books. They took 2 groups one on IDF of 2,000 one day and 500 the next, as I recall, and the other group 1500/day. The total cals/week worked out pretty much the same. and the results after a year were pretty much the same. I think the difference was in blood chemistry. I’ll leave researching that to the reader. ;-). Up until the end of last week I was in a perpetual 21/3 fast..that is 21 hrs of fasting 3 hours of feasting every… Read more »
Woot
Guest

I replied to you above but can’t edit it to add… I don’t lose weight eating this way, either. I have to do 24+ hour fasts to see weight loss.

I think it depends on how insulin sensitive you are. My insulin is a bit messed up. What really worked great for me was switching it up a lot, being irregular about length of fasts. This suits my personality & lifestyle anyway. Anything I do very regularly, my body will adjust to.

Walt
Guest
I hear ya, they should allow, if not edit, delete such that one can copy into clipboard, delete, add another comment, paste, and edit, like on tweeter. For the longest time that’s effectively what I was doing a 21 (or 22 or 23) hour fast every day. I lost a few pounds then stopped losing. On fasting talk Megan poo poo’d that as there is no fasting that is reduced calorie and reduced calorie doesn’t work. WAIT… that is fasting for 20+ hours and feasting for 1-4 hrs. Even in CGF, if not OC, Fung writes that will provide slow,… Read more »
Doug
Guest
Walt, you said: “They took 2 groups one on IDF of 2,000 one day and 500 the next, as I recall, and the other group 1500/day. The total cals/week worked out pretty much the same. and the results after a year were pretty much the same.” Makes sense to me. I think the important differences will be in what works best for a given individual. A steady 1500 calories per day would not work well for me, whereas repeating 3000/0 would be better. In reality, I’m very disorganized about it, but persistent. Some days start as total fasts, but end… Read more »
Walt
Guest

Yep, I agree. They did not mention blood chemistry at all so they were just focusing on weight.

Laurie
Guest

I am new to IF and have struggled with understanding the concept, until now. Thank you for explaining it in simple terms that are easy to understand!

Svavar
Guest

One guestion. How would one increase his metabolism back to prior levels, assuming he has CR for a while and f.x. lowered his metabolism from 2000cal to 1500cal?
Would fasting here help or hurt in the effort to increase metabolism back to prior levels?

Walt
Guest

An essential question Svavar. I looked long and hard for the answer and just recently got it.
Longer fasts, eat lots of fat.

MikeT
Guest

If you have lost weight, your resting metabolism will be lower. Even if you change your muscle/fat ratio, it will not make much difference. Smaller body = less calories. You have to get used to exercising more if you want raise your overall TEE.

Svavar
Guest

Thank you for you comments Walt and MikeT.

Tina
Guest
Is intermittent fasting (18 hours no eating just coffee and water) enough to lower insulin? I enjoy my meal time with my family at night, so the 24+ hour fasts are difficult. I have 10-15 pounds to lose to get where I want to be. I’m a size 4 but super flabby and very small boned. I lost my baby weight after my first two kids by cutting carbs and running. After my third child I’ve struggled with the last 10-15 pounds. Also how bad is it to drink wine as fas as causing or leading to insulin resistance. I’ve… Read more »
Stephen T
Guest
Tina, 18 hour fasts are easily long enough to take you into fat burning mode, assuming you’re not adding milk to the coffee or consuming large amounts of carbs before you fast. Our body uses the carbs first before going to the stored fat. When we eat we generate insulin, then it comes down. Once our insulin level drops, we can access our fat stores for fuel. I exercise regularly, and it’s beneficial in many ways, but nearly irrelevant for weight loss, unless you do ridiculous amounts. Exercise is good for our health and keeping the body firm, but essentially… Read more »
Paul
Guest

Hello people, I want to share this study with you:

“Insulin Resistance as a Predictor of Gains in Body Fat, Weight, and Abdominal Fat in Nondiabetic Women: A Prospective Study”

http://onlinelibrary.wiley.com/doi/10.1038/oby.2012.44/epdf

Do you think that there are factors that have been overlooked? I want to hear your thoughts, this really confuses me…

Woot
Guest

There is something interesting that happened in this study. The women who didn’t complete their food logs and dropped out? When they followed up with these women later, there was NO difference in the high-low insulin groups. Only the women who kept their food logs the whole time had a different outcome!

It makes me wonder if the fact of keeping a food log and being followed made some of those with high IR (bad eating habits) a bit more aware of what they were doing – so they saw the best outcome.

Paul
Guest
Thanks for your comments, your supposition about the high IR group is exactly what the researchers thought too: “Although there was no intentional treatment or intervention associated with the present study, women with the highest body at levels initially, and therefore the highest levels of IR, may have been more motivated to lose weight following the baseline assessments than the leanest women, who were more insulin sensitive. Differences in motivation may account for differential behavior change, which could explain why those with the highest levels of IR (and therefore the highest initial weights) tended to gain less weight over time… Read more »
monica
Guest

I didn’t find that that there were any (biological) differences in weight changes between the three groups; in 18 months, gaining 1 kg or losing 0.5 kg is about the same to me, even weight fluctuations from day to day would explain them.
As far as insulin resistance being helpful in weight loss/ maintenance, that might be the reason fro the HFLC advantage, if there is one: when the body ignores insulin signaling, fat is being released from fat stores…

Parth
Guest

What happens if I eat say 50-100 calories worth of carb in form of a biscuit or a bread while being on fast? Do I immediately go to burning carb but it won’t be enough for more than an hour so what happens after an hour because insulin will not immediately go down if I understand correctly ? would I suddenly start feeling tired after a while?

deirdra
Guest

It depends on the individual. 50-100 calories worth of carbs in a biscuit or a bread would make me feel exhausted and wanting a nap within an hour, make me hungry & obsessed with food and stop my bodyfat-burning for 2-3 days. But others would have no problem eating 12-25 g of junk carbs.

Lori
Guest

A spoon of nuts or other fat would be a better option

Stephen T
Guest

Parth, the biscuit or bread ends your fast because it will generate an insulin response and turn off fat burning. It may well make you feel hungry when the insulin brings your blood-glucose back down.

Mathieu
Guest

A good diet, even with moderate carb (adapted to the activity), with whole foods (and thus low on insulin response), is also effective at losing fat.
Although ketosis/fasting is the “optimal” approach (I still find it a bit to extreme if you’re not obese or with a medical condition requiring it), it doesn’t mean it is the ONLY solution to lose fat.

Dr.Rob
Guest

Technically it’s true. But emotionally this is not what we want to achieve. Right now, we don’t recognise and even ignore or despise the most powerful tool which is fasting followed by lowcarb/keto. We must talk about it and bend public attention. Of course you can loose weight on plant only diet – it’s low on insulin. But you see, the thing is the insulin response and we want to maximise it. It happens by doing fasting. Nobody denied other ways of loosing what, they are just not interesting for us.

Mathieu
Guest

Why plant only diet ? Why Dr. Fung compares his approach to 6 meals a day of white bread ? As if there is nothing in between, healthy and with low insulin response, without having to go keto or extended fasts.

William Brady
Guest

When you fast you enter ketosis, which is the result of your body making ketones to fuel the brain from fat. How is it that I remain in ketosis, as measured by keto sticks, after having eaten low carbohydrate meal of salad, nuts, seeds and dressing? I think this suggests a special case of a dual track, doesn’t it?

Walt
Guest
All foods, carbs, proteins, fats, add calories. Your body has a set caloric requirement. If you are in a keto adopted state and you add 200 cals or more it is stored in the liver as glycogen. At that level it is converted to glucose and used very quickly if it wasn’t used upon digestion. That is way under your body’s requirement so it would resume converting fat for kidneys, heart, the 25% of brain that cannot use ketones. If you ingest enough to derail ketosis then you body would have to reestablish that state. I was told having a… Read more »
William Brady
Guest

Thank you Walt. Sounds like we are from the same age group.

How accurate is the Ketonix breath analyzer and what is it measuring?

Walt
Guest
It measures breath acetate that is a byproduct of ketosis. Here is a link to some charts https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4737348/figure/oby21242-fig-0001/ used in the following really good answer to your question: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4737348/ With the use of these and the following conversion chart http://www.ucdenver.edu/academics/colleges/medicalschool/centers/BarbaraDavis/Documents/book-understandingdiabetes/ud29.pdf It’s actually pretty good. I used to use keto stiks but, well, it’s a little messier than I prefer. The figure 1 chart shows the range in PPM for ketogenic diet in an adult. I am routinely on there originally in the middle, now at the top. In figure 2 you can see towards the top right the variance between… Read more »
William Brady
Guest

Thanks so much fun all of this information. ?

Brian
Guest
I used to be fit and fat. I have weight trained regularly for the last forty years. At one point, as I went through a power lifting stage, my weight went up to 290 lb. Although I was extremely strong, I also developed metabolic syndrome, so I needed to change my ways. As Dr. Fung points out, losing the first 10% of body weight is relatively easy. It only takes a few months and can be done with a variety of dietary internventions. Usually, however, a weight loss plateau ensues, and in my case it was extremely difficult to get… Read more »
Walt
Guest
Slightly different topic. I have long wondered about ‘damaged’ metabolism. I know of the medical way to test, involved and expensive. I believe I have devised a pretty good substitute. It involves fasting for, ideally, at least a week. Once in a fasted state, ketone at 40mg/dl or better or maybe 80mg/dl. higher is better 1) weigh yourself 2) do not ingest food for 1 week 3) weigh yourself again 4) multiple (end weight – start weight) by 3,500 and divide that by 7. 5) that number should be your TEE 6) if you did not workout or go to… Read more »
Doug
Guest
Walt, on “damaged metabolism” – I’m assuming this means lowered…? I think your 1.2 multiple for resting energy expenditure (normal living, not working out) versus the basal metabolism is right on, i.e. our heart, lungs, brain, liver, and kidneys use up around 75% or 80% of the calories, with muscle tissue burning the rest. With that as a given, there doesn’t seem to be much room for much decline, unless the body really thinks it’s starving and drastically slowing things. I know some people don’t take well to fasting, but – anecdotally, to be sure – I think more people… Read more »
Walt
Guest
Doug, 500 may be something of an exaggeration. However, in the Ken Hall research on season 14 of Biggest Loser some of the dropped metabolism of the contestants was upwards of 600cals below what Mifflin St Jeor would have predicted. If the body did that in the attempt to for it gain weight on the food you were consuming. What Dr Fung has said and Megan Ramos has said is, as I answered up top, fast for longer periods of time and eat more fat. What neither has said is whether that is a permanent condition or temporary. For those… Read more »
Doug
Guest
Walt, wow, man – such a drastically lowered metabolism must make the person feel like absolute heck. While I don’t know, my gut feeling is that the body will continue to adapt to whatever the current conditions are, after getting the boost in HGH and adrenaline, so likely going back to a relative more “normal” state when the fast ends. Fasting 3 days per week = very restricted indeed, and I would certainly hope that such is not required to maintain one’s desired weight. However, being mindful of calories and the whole ‘permanent lifestyle changes’ deal no doubt applies, for… Read more »
Walt
Guest
Fascinating stuff indeed! Fung and Ramos are conspicuously absent on what return to normal life is. That may be because they assume so long as you reduce sugar, reduce refined carbs, fix your problem and return to the new normal, reduced carbs. That would work for me. However, following my thread, and this is insufficient sample size my TEE has been approx 1200cal/day. That is with, perhaps, 325cal burned 5 days / week. The interesting thing is, Fung, as best I can tell, doesn’t actually push ketogenic, rather fasting, neither does Mosley, he favors Mediterranean diets and 5-2 fasting. Even… Read more »
NicoleS
Guest
They left the podcast because Jimmy Moore and Megan and Jason had different views on how the show was conducted. My understanding was they wanted it more professional (less goofy) than Jimmy Moore. This caused a rift and they went their separate ways. The hope is they start their own podcast. Walt – I am an engineer as well but I think you are focusing too much on a “one-fits all model”. Although questioning everything is never a bad thing. The thing is – your puzzle is for you to solve, as my puzzle is for me to solve. Each… Read more »
Walt
Guest
Nicole, thanks for that! Yes indeed, I also complained about the giggles and yucks…very unprofessional. It does seem like it broke all of a sudden, As of June 2nd Dr Fung and Jimmy were planning their July joint podcast. What you said makes perfect sense as I was getting to the point where I was seriously questioning the utility. It did strike me the three of them routinely contradicted what they had previously said. I don’t see the value of turning over Megan’s old role at IDM to her husband. Who’s going to pay money to talk to someone who… Read more »
Roger Bird
Guest
There is no mystery about when your metabolism takes a dive. Put your hands on your kidney area (best) or just your tummy, and if they are really cold, then your metabolism is down, unless your hands are cold for some other reason. For me putting my cold hands on my kidney area can be shocking. If you are lethargic and have cold feet and/or hands, then your body is trying to track your reduced calories in. This is not the end of the world. Just keep on track with the no calories and Mr. or Mrs. Body will grasp… Read more »
Walt
Guest
That’s interesting Roger, thanks! However, another question I have is this. Given the ‘magic’ of fasting comes at day 5+ with phase 5, Protein Protection, which is where there is a surge of HGH and adrenaline. Presumably once you break the fast the adrenaline and HGH stops thereby lowering metabolism . The prologue to my above post was this. I’ve been dieting, either formally, Atkins, weight watchers, etc for some time and had pretty good luck short term. By that I mean 36lbs or so. 2 years ago this summer I was diagnosed w/T2D and went full bore on the… Read more »
James
Guest

Could somebody in Walt’s real life intervene and help him with the manic episode he is clearly having?

Walt
Guest

Absolutely Jimmy, if you don’t have anything constructive to add, troll. So dignified, so adult.

Kayleen
Guest

When fasting what can be done about getting a bad taste in your mouth? After a week. Thank you;)

Walt
Guest

Kayleen, by “bad taste” is it maybe fruity or a little bit like nail polish remover? When in ketosis acetate is exhaled and that, depending on what you mean by bad taste, could be what you are sensing. Try mouth wash or brush your teeth more regularly to act like mouth wash. A week would be about the right amt of time.

Charlene
Guest

Perfect analogy & the visual–made it crystal clear.
Thank you

bcarney
Guest

hypothetical:

-eat 2000 throughout the day, staying in “fed” mode” – body uses those calories and doesn’t burn fat, stores excess
-eat 2000 at one time, body uses some, stores the rest, then uses those stores during the rest of the day as needed

What’s the difference, doesn’t it still come down to calories in vs calories out? A slight calorie burn increase from not slowing metabolism is the only one I see.

Doug
Guest
Hi bcarney. I agree – many times there won’t be much if any difference, there. If insulin resistance is a problem/concern, then eating many times versus once would usually result in higher insulin levels, on average, but one’s weight would not be much affected, I think. If one doesn’t have a problem with insulin levels and one maintains a constant weight at 2000 calories per day, then things are balanced and it’s as you say. Where I can see a possible difference is in cases where the person is burning less or more than 2000 calories a day – persistent… Read more »
Doug
Guest
On “returning to normal life” after we reach a desired weight, things are not adding up for me. During 30 years of often horrendous excess, I “only” gained an average of 5 lbs. per year. At 3500 calories per pound of body weight, that would total 17,500 calories. *Or* – an average of 335 calories per week. Wow – that seems so little to me. As in would I have actually stayed the same weight had I merely consumed 335 less calories per week? “Excess” – a big day for me would be something like having 4 bacon, egg and… Read more »
Walt
Guest
Doug, I think the key is knowing what your body is doing. By that I mean, Mifflin-St Jeor is a recognized and standard measure for one’s estimated REE. There’s another equation added to that REE, it’s a hyphenated last name, that adds the factor for activity level. It’s an average which means for all those outside of, say, mean +/- 1 std deviation, it simply doesn’t work. I think it comes down to this, what is one’s actual REE and from that factor activity to determine TEE. The next thing is how sensitive are one’s cells to insulin? That can… Read more »
bcarney
Guest
Doug
Guest
Walt, that sounds very sensible. Seems to me that the “all bets are off” also applies when eating a vary large amount of calories, often – that we won’t gain as much weight as we should, just going by caloric calculations. Not that that’s a bad thing. At another end of the spectrum, the Mifflin-St. Jeor equation paints a fairly strict picture for those who are at a desired weight, i.e. there won’t be many calories to play with, before one gains weight. So, and no surprise – looks like we also need some persistent and high effort to stay… Read more »
Walt
Guest
Mifflin-St Jeor is based upon a normal metabolism. Perhaps a statistically avg metabolism. You throw in Biggest Loser contestants or someone feverishly working out at the gym to drop and they don’t have normal metabolisms. The reason I mentioned that is from an earlier post of your about where the starting line is. What I was attempting to get at with Nicole, I honestly don’t care if one does caloric reduction or intermittent fasting or CICO. What I care about is how is it that fasting 21 hrs/day and eating 3 hrs …well that is just wrong and will lead… Read more »
r41nier
Guest

Well maybe when your fasting Calorie Reduction becomes Secondary or just a side effect of the Intermittent Fasting. I think it’s just a matter of semantics. So maybe Dr Fung is right in that CRaP will not work if you use it as the primary basis of your diet.

Erik
Guest
These illustrations are a little too simple. I get that the BMR drops to support the reduced calories in, but caloric restriction obviously doesn’t STOP people from burning fat for energy. The whole issue with The Biggest Loser diet is they lose the fat, but their BMR is so jacked it all comes back when they can’t keep up the diet. These posts don’t illustrate that mechanic and instead describe an on/off switch for fat burning. How are people on conventional diets losing fat in the beginning and at what rate does the BMR slow to match input energy? I… Read more »
Sean Raymond
Guest
It is very important that people appreciate that lipolysis does NOT = lipid oxidation. Even if insulin is low, and lipolysis is activated as in the fasted state the fuel mix is NOT 100% fatty acids liberated from the fat stores whilst the body will only burn what it needs to. Numerous metabolic ward studies have now shown that reducing insulin does not = enhanced fat loss despite the anticipated increase in lipolysis. I repeat – the body will only burn what it needs to. Sad to say but the weight loss in any study, be it low CHO or… Read more »
Olga
Guest
Hi there! I have been almost professionally involved in sports (working out even 8-9 times a week) and tried really tons of different eating plans/patterns. I always had a great problem with hunger (especially hunger for sweets) and the more often I eat the worse it got. Despite a really huge amount of workouts (I am a long-distance runner and a crossfitter) I have never fully met my fitness and weight goals. No matter how much I exercised (and how intense workouts I did) I just couldn’t get below 22/23 BMI. In the case of running, it’s extremely important to… Read more »
Chris
Guest
So I have just started intermittent fasting. During my fast I drink coffee and “Diet” cranberry juice. It has 5 calories per serving and 2 carbs. I also water it down at a 50/50 ratio so you can cut those numbers in half. I probably drink 64oz of this %50 mix per fasting day which means 32oz is the juice. That means I get 20 calories and 8 carboydrates. Is that enough to take me out of ketosis? Should I switch to straight water and coffee which have zero calories? Also I take medicine that requires food so I usually… Read more »
Sebastian perez
Guest

Dr. Fung, please answer me this one question… If fat has virtually no effect on insulin and without an insulin spike there is no fat storage then in theory, I could ingest unlimited fat and lose body fat? Please explain this relations between low insulin calories and body fat reduction/increase.

Thank you kindly for all you provide us.

Audrey
Guest

Dr. Fung.
Speaking as a desperate post-menopausal woman who has been “dieting” for decades, and proving everything you’ve said, I just want to thank you for giving me this exciting lifestyle change. I have only been fasting for 2 weeks but I already see results and I am loving my 18/6 fasting routine.

Thank you. Thank you.
Audrey

pattyloo
Guest
After listening to hours of Dr. Fung’s free youtube lectures, I just finished 1 week of OMAD (1 meal/day). I lost 2.5 lbs in that week, which is great. I’ve been listening to a lot of keto info on youtube, and that food looks really good! I’ve decided to combine keto with my fasting. I do have questions about exactly how much I can eat of the keto food, and how many hours of fasting, etc. But, I plan to just try the OMAD for a week on keto and see how it goes. I do plan to try longer… Read more »
Hunter
Guest
Hello! I’m a very curious individual who has a lot of questions about what the best ways to do things for your body are, specifically losing weight and have been looking at a lot of anecdotal evidence for years. > The key to successful long term weight loss is not reducing calories. It’s reducing insulin Is it fair to say this line above? What about the doctor that went on his twinkie diet + veggie/protein/vitamin supplements? He had to be spiking the crap out of his insulin constantly while losing over 20 pounds regardless of how unhealthy it was. I… Read more »
BobM
Guest
I fast many different times. I do fasts daily until about 1-2pm, although sometimes I eat breakfast. Sometimes I fast until dinner. Sometimes I fast through dinner until “lunch” the next day. Sometimes I fast 3-5 days. I mix it up. Sometimes I fast a lot, two 40 hours fasts plus a 24 hour fast per week. Sometimes I fast a little. This week, I’m doing 18 hours fasts before I go on vacation, then I won’t fast much when on vacation. When I get back, I’d like to try a 1-week fast. We’ll see – the weekend is the… Read more »
BobM
Guest

I should say that I try to fast every week, with exceptions around vacations and maybe every once in a while to take a break and keep my body guessing. There are no rules for fasting. I personally have a hard time during “reentry”. I basically have water in me, and it takes a while for me to settle down, usually a day or more for fasts of several days. So, I make sure longer fasts are not near days I travel. Others don’t seem to have this problem to the extent I do.

Lori
Guest

BobM

Not sure exactly what you mean but I find psyllium fiber taken a couple of hours before or the morning of the end of the fast and the next day help tremendously. I forgot during a recent fast and it was not pleasant

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