How to Fix your Broken Metabolism by doing the Exact Opposite

We saw last week with the Biggest Loser study that basal metabolism plummets when you lose weight with calorie reduction. As contestants lose weight, they burn a lot less energy – up to 800 calories per day less than before. Some of that is expected, since there is less body tissue to maintain, but nevertheless, these contestants burn far less than expected even taking this into account. Even 6 years later, their basal metabolic rate (BMR) remains depressed, as do the contestants themselves. The story got a lot of coverage, but one thing was consistently missing. How to fix it.That’s what I’ll show you today, and it’s the opposite of what most people expect.2CompartModel

So, let’s think about this problem in the context of the 2 compartment model of obesity that we have used before. There are two compartments for body energy. We take calories in as food. This gets stored in the short term as glycogen, or long term as body fat. Glycogen is easily converted to energy (calories out), but body fat, not so much. So we can consider the analogous situation where short term energy is stored in a refrigerator and long term in the basement freezer.NewHOT12

Insulin’s role is to direct food into the basement freezer. When there is excess food that can’t be kept in the fridge, insulin directs it to the freezer. This is body fat and manufactured in the liver by the process of de novo lipogenesis. What causes insulin levels to be elevated depends partly on the foods we eat, but also by insulin resistance.

Fructose, for example, plays a key role in elevating insulin resistance which will, in turn raise insulin levels. Insulin resistance leads to high insulin levels, which leads to higher resistance in a vicious cycle. That is, it can be self sustaining.

So during weight loss, if we don’t address the long term issue of insulin resistance, then some of the incoming energy is directed toward storage of fat. At the very least, we won’t be burning fat. Our basal metabolism gets energy from two sources – food, and stored food (fat). If high insulin levels blocks our access to fat stores, then all of our energy must come from food. If we have reduced food intake from 2000 calories per day to 1200, but basal metabolism must also fall from 2000 calories to 1200.

This is the logical response of the body. Where would it get energy from? Fat stores are locked away since high insulin will block fat burning (lipolysis). So, as ‘Calories In’ goes down, so does ‘Calories Out’. This is why the Biggest Loser contestants metabolisms plunged so heavily. This is the fallacy of the Caloric Reduction as Primary crowd. They only care about reducing calories in, and don’t realize that the game is all about ‘Calories Out’.

Consider the analogy of soccer. Soccer’s First Law of Thermodynamics says that to win, you must have more ‘Goals In’ than ‘Goals Allowed’. Goals can’t be created out of thin air. So, therefore if we increase the numbers of ‘Goals In’, we will win every game. So, we move our goalie and position players all to forward and ask them to stay in the attacking zone. Of course, we lose every single game. By trying to increase ‘Goals In’, we’ve increased ‘Goals Allowed’. The mistake is to assume that increasing ‘Goals In’ will not affect ‘Goals Allowed’. Then we blame players for not trying hard enough. But, in truth the strategy was bad.

Same goes for ‘Calories In’ and ‘Calories Out’. Reducing ‘Calories In’ will result in reduction of ‘Calories Out’. You’ll lose every single time, as the Biggest Loser proves. The mistake is to assume that reducing ‘Calories In’ will not reduce ‘Calories Out’. But it does. Every single time. Then we blame patients for not trying hard enough, but in reality, the strategy of ignoring insulin is bad.

How to Fix your Broken Metabolism

So, are we doomed to a life of ever growing waistlines? Hardly. Remember, the key to weight loss is to maintain energy expenditure (calories out). If you simply increase food intake again, you’ll simply increase weight. So, what to do?2CompartFasting

There are two compartments here. The body will get energy from food, or stored food (fat). So the answer is to unlock the door which is preventing us from accessing out fat stores. It is the high insulin levels that is keeping all the energy locked away in fat. Insulin is blocking the door so that we can’t get to that basement freezer. Once we understand that, the solution is simple. We need to lower insulin. The key is to release all the pent-up energy stored in the body fat. The crucial junction in weight gain/loss is not the calories, it’s the insulin because that is what opens up the door to release the fat for burning.

Lowering insulin will allow fat burning (lipolysis). This provides our body with lots of energy. If we have lots of energy coming in, the body has no reason to shut down its basal metabolism. The quickest, most efficient way to lower insulin? Fasting. Ketogenic diets will work, too. But remember that insulin has many inputs and is not simply carbohydrates. Cortisol, protein, fructose, insulin resistance, fibre, vinegar and countless other things play a role in determining insulin levels. Generally, though, cortisol and insulin resistance are the things least likely to be treated.

Once the doors to the ‘fat’ freezers are open, the body says, “Whoa, there’s lots of energy here. Let’s burn a little extra”. Studies of fasting show that basal metabolism doesn’t shut down during fasting, it revvs itself up. Four consecutive days of fasting increases basal metabolism by 13%.Heilbronn5

Studies of alternate daily fasting (ADF) shows the same thing. Basal metabolism is maintained, even over 22 days of ADF. Even with weight steadily decreasing, the resting metabolic rate is statistically identical at the end of 22 days. You can see from the table below, that carbohydrate oxidation plummets as fat oxidation rises, just as seen previously.

This is an important point. In standard caloric reduction strategies, the body reduces its caloric expenditure to adjust to the reduced caloric intake. Stores of energy locked away as body fat are not available. If your reduce your calories from 2000 to 1200 per day, then your body is forced to reduce calorie expenditure to 1200 per day since it cannot get any from the stored food (fat). Where’s the extra energy going to come from?

However, by lowering insulin drastically during fasting or alternate daily fasting, the body does not shut down. Instead, it switches fuel sources. No food in coming in. Insulin falls. Your body has a choice. It can reduce calorie expenditure to zero, also known technically as ‘dropping dead’. Or, it can force open the reserves and power itself from fat.TEE

Lowering insulin makes it much easier to open up these stores of fat. That it’s normal job. When you eat, insulin goes up, fat goes into storage. When you don’t eat (fast), insulin goes down and fat comes out of storage. Dr. David Ludwig showed a similar result when comparing diets. In his study, he compared the total energy expenditure after weight loss with three different types of diets – low fat (standard advice), low glycemic index and very low carbohydrate.

The low fat diet does nothing to reduce insulin levels. So fat stores are blocked from being used for energy. Basal metabolism drops almost 400 calories per day. But on the other extreme, very low carbohydrate diets would be the diet that lowers insulin the most. This allows access to the basement fat ‘freezer’. Now our body has the energy it needs to start revving up its metabolism.

It works with surgically enforced fasting such as seen with bariatric surgery, too. The one contestant, Rudy Pauls, who got bariatric surgery fixed his wrecked metabolism. So, is it possible? Definitely. Rudy Paul’s metabolism had slowed more than any other contestant. That’s why his weight regain was so dramatic. By forcing himself to fast, he has partially repaired his broken metabolism.biggest loser clip 3

In order to fix our broken metabolism, we need to allow free access to the energy contained within our fat stores. We need to allow fat burning (lipolysis) to proceed normally. We need to lower insulin. The answer is low carbohydrate diets, or even better – intermittent or extended fasting.il_570xN.380160499_gd9j

Fasting maximally lowers insulin and ignite the flames of fat burning. Caloric reduction wrecked our metabolism by causing it to shut down. How to fix it? Do the exact opposite of what you expect. Push your caloric intake towards zero! This is the George Costanza method. If everything you do makes things worse, do the exact opposite. It does not matter if you think it doesn’t make sense. Do it anyway and see what happens.

The standard nutritional advice given – to Eat Less and Move More is so bad, that doing anything, even the exact opposite beat it.

129 Responses

  1. Dr.Garry Lee

    I think the best thing is LCHF plus fasting if needed, and as much as is needed. I hardly ever do it other than by accident. You do feel really sharp when you do it, though.


      I think this is a good choice, I use it to control my diabetes. This article is right on, it is all about insulin. When insulin is high you can not use stored fat. There was a fat rat experiment where rats insulin was kept high, they starved to death, fat. The fat could not be used because of high insulin levels.

    • For me Low carb barely made a difference. I really noticed a difference when I started the fasting.

      • For some one who is new to this, what fast recommendations are there? Looking for recommendation of frequency and duration. Also do you continue taking your Diabetes medication during this process or do you stop?

  2. Thank you, once again, Jason, for a fantastic post!

    Love your sense of humour…….

  3. Joaquim

    I’ve been in LCHF diet plus fasting every day (alternating 16h/24h) and the results are outstanding. Lab and life style reflect the good results I achieve. Took almost a year of preparation for that, but it worth every effort.

    • Hi Joaquim,

      Do you eat lunch and dinner one day and only dinner the next day? Or lunch and dinner one day and nothing the next? I’ve been using longer fasts (say 2+ days) but am thinking of eating lunch and dinner twice a week and only dinner three days a week, for the workweek. Then probably eating lunch and dinner Saturday and Sunder, although I might eat breakfast every once in a while.

  4. Samantha

    I appreciate these concepts, because like you, the bottom line is to help patients, not to subscribe to “correct dogma.” Understanding various theories can help a clinician when successful weight loss or health improvements are not occurring with a given strategy. We must all be willing to change a failing strategy. It is good to have a voice for fasting simply because our society has nearly erased all traces of the practice. It’s the antithesis of consumerism, no shopping, no prep, no expensive kitchen gadgets, no clean up, and no food. Vitamin or electrolyte supplement companies may perhaps be the only ones that can make bank on people who frequently fast. In any case, this is information that I frequently share with other healthcare providers and patients with a goal to help them understand that fasting is a legitimate, evidence-based and time-tested strategy to improve heath. Truly it is so odd to me that we ever believed we must eat all the time…or else!

    • I think the idea of eating all the time came from stabilizing blood sugar…for diabetics. They then assumed that this would apply to everyone. This is of course incorrect and has caused major damage (as has the whole low fat debacle). But I think they meant well.

    • spot on Samantha

    • I wish I had a health care provider like you in my life, Samantha!

  5. Thank you Dr. fung, I too love your sense of humor and always look forward to your new blog postings. Thank you for taking the time to keep us all inspired and on the right track. Your book was also great!

  6. I met with my endocrinologist yesterday and they said, “Fasting in the long term will make insulin resistance worse”. But when I wasn’t fasting my numbers hardly improved, but yesterday my results showed improvement after I started fasting. I feel so bad because so many people get bad information from doctors who don’t know any better.

    • johnnyv

      Very concerning that an endocrinologist doesn’t seem to understand the very large difference between pathological IR as seen in T2DM vs physiological IR as seen in LCHF/fasting.
      Did you ask them to explain how this actually occurs?
      Also how fasting doesn’t result in very high blood glucose if that was the case?

    • Josette Eral

      Isn’t that sad. I don’t trust most doctors and really never have. I guess I just follow my gut and what feels right.

  7. But if we fast aren’t we really Eat Less (zero/very little food coming in) and Move More (more energetic that makes us move more)?

    • tony my understanding of the article is when low calorie diet the body wont go to fat store and use food ingested all the while insulin levels remain high further blocking the burning of fat. In fasting insulin levels leading to fat burning.

      • I meant to say insulin levels drop leading to fat burning when fasting.

    • All foods induce an insulin spike, putting the body into a fed state – lipogenesis. When you are constantly snacking and constantly eating, you are keeping the body in a Fed state with high insulin, where your body is not pulling energy from fat stores.

      This is different than bringing your insulin levels low enough to enter a fasted state lipolysis in order to oxidize and free up fatty acids from fat stores for energy.

      • Hmmm, I don’t quite follow this explanation. It is well documented that people following a low calorie diet DO in fact lose weight. Their fat stores are obviously accessed. I myself have experienced this throughout my lifetime. There is lipolysis going on. If there were not, then how else do contestants in the Biggest Loser manage to lose weight? I am not defending their approach by any means. They do of course gain the weight right back and their metabolisms do slow down.

        I wholeheartedly agree that Fasting is obviously a better choice and works much better for weight loss and long term weight maintenance. I have used it successfully for over a year now. But to say that the body cannot EVER access fat stores while insulin is high does not ring true to me. Or maybe i’m just misunderstanding.

        Detoxes have become popular in the last several years. I know of some that require a regime of nothing but honey or maple syrup mixed in water taken throughout the day. These people lose body fat, even after constantly spiking their insulin several times a day.

        I have the utmost respect for Dr. Fung and his work. I do not mean this as an attack. I am just asking for some clarification.

        • You are right Tony low calorie diets do use fat when they are severely restricted. Somewhere on this site is post comparing diets reduced by 25% of calories to fasting. In that blog post Dr Fung talked about insulin levels staying high and blocking fat loss.

        • I think you have to consider short term fat loss compared to long term. Low calorie intake may force your weight down in the short term, but your body will keep fighting you every step of the way, and eventually ‘win’. By lowering your insulin and cortisol levels and reducing resistance, you are lowering your set point, and thus your body will not fight to maintain the higher weight.

        • That’s a really good point. Plus intermittent fasting hasn’t come into vogue until the past five years, but there were many people before that who lost weight and stayed thin on a healthy diet with regular exercise. I’ve been doing intermittent fasting off and on for the past three years. I’m on it now doing one meal a day with about a 22-hour fast and exercise about five times per week, and I’ve lost 13 pounds and I feel great with very few food cravings. But when I stop my daily fasting, my weight increases relatively quickly. I think the evidence is pretty overwhelming that fasting has some real health benefits, but I don’t think its conclusively been proven that intermittent fasting creates changes in the body that prevent yo-yo dieting.

    • I agree. It is misleading to claim that eat less, move more is that off the mark. If fasting isn’t eating less, I don’t know what is. Doeesn’t the body have to have a caloric deficit to even want to get the fat out of storage? Are people eating 2500 or 3000 LCHF calories a day or more and still losing weight? Because I’d guess that most overweight people are eating that much, so of course if they go LCHF and end up eating 1800 calories a day, they will lose. I can accept that when they do lose, their bodies’ metabolisms don’t drop, and that is a definite advantage. But show me overweight people who are eating MORE calories after, say, a 20 lb. loss, and maintaining or losing more. If calorie deficit plays no role, then they should be able to eat even more and still somehow take fat out of storage. I make the loss small so that there theoretically isn’t that great a mass loss necessitating a drop in intake.

      Has anyone every proved that more people maintain weight loss after LCHF? Because a 2007 metastudy of weight loss by any method found that the norm was weight GAIN two years after going on any “diet.” It’s possible those with true health issues may have better compliance later, but maybe not. It’s quite likely that a majority of those in degenerative disease condition in “rich” countries could reverse it with much more modest changes than Fung recommends, but they don’t do it.

      I lost 40 lbs. over time just with “fasting” between three meals most days of the week, but I had good blood readings and wasn’t in a hurry so it took a few years. I believe MOST overweight people don’t need much more rigor than that. I think in one of his blogs, Fung even recommends it. Unless someone shows signs of disease, that seems like the first step to take.

  8. leavemealonegoaway

    Agree w Dr Garry Lee. There is that dreaded keto flu that I experienced week one of VLCHF… and I was still eating!

    I can’t imagine going through that transition AND enduring my first 24 hour fast. Once that ‘hangover’ feeling kicked in, I’d probably never try it again. I suspect people who try 16:8/short regimens and feel ok aren’t really tapping their fat stores too much.

    I tell my friends who want to try to do a 2 week or longer VLCD (eg, get the flu out of the way, and THEN introduce different IF regimens. Virtually effortless.

    • Brendan F

      The “keto flu” is usually a result of electrolyte(salts) deficiency, by the way (too little sodium, magnesium and/or potassium). On a ketogenic diet, you release more electrolytes, and early on you release a lot of the stores along with the water. On top of that, most ketogenic foods are not as high in various electrolytes as many high carb foods (and especially processed foods), so you need to do some extra planning to make sure you get enough salts, and that will help completely avoid the keto flu. First few weeks may still show weaker performance otherwise while adapting, but you shouldn’t get headaches, cramps, etc (that’s a sign something is missing).

    • When I eat myself out of ketosis, and drop back into keto, my keto flu lasts about 10 mins. I have on occasion dropped back into ketosis while still eating. of course in the last 6 months I must have spent less than 3 hours out of ketosis.

  9. The opposite of “Eat Less, Move More” would be “Eat More, Move Less.” Those who are already familiar with your writing may get what you’re trying to say but the analogy/semantics fell apart somewhere. (In a way, one is “eating” more by fasting because one is accessing the thousands of calories in stored fat.)
    Vinegar & fiber are mentioned but thee is really no explanation of what they do. If you’ve written about them before, could you please link to the articles?

    • leavemealonegoaway

      Hi Sloan

      My take was that “Reducing calories wrecks metabolism”, so what’s the fix? The ‘obvious’ answer would be “Stop reducing calories!”; the opposite of this ‘obvious’ answer is “Drop calories to ZERO!!” (intermittently).

      Agree that hyperlinks to the alluded factors would be nice. However, taking a weekend to read every single post from day one is even better..and it’s worth it! 🙂

    • Hi Sloan, there is a search box near the top, just type in and the appropriate articles will appear.

    • honeycomb

      Go to the search function and type them in .. they’re there .. it worked for me when I tried it.

    • Sloan,
      That is not a falling apart at all. It is the exact answer. You need to eat more of the correct foods and stop doing hours of useless exercise.

  10. Dr Fung: I gotta say that as a layman who has studied the diet/nutrition/health axis intensely for many, many years, I find that your work has floated to the top of my pile of the incredible Docs and scientists who take the time to post about the science of optimal health.

    Clearly keeping the pancreas as quiet as possible is the critical path for sustained lifespan/healthspan. Thanks for taking the time and making the commitment to do this great work!

  11. Greetings again Dr. Fung….another great post. I hope I’m not being a bother but may I ask again for a post on fasting and CKD/ kidney health? Surprisingly I can find very little on the subject other than a great article by Robb Wolf. Many of the fasting “haters” out there mention potential negative effects on kidneys if fasting. Of course, being a Kidney Doctor, I’m sure fasting has, at the very least, no major negative effects. Robb’s article mentions a case in which three weeks of hclf led to CKD recovery.

    Again…many thanks!

  12. How does vinegar help or derail us? What impact does it have on our diet?

    • leavemealonegoaway

      Typed ‘vinegar’ into the ‘search engine’ at the top of the page. Here’s one of many things that popped up:

    • It lowers insulin. Some IF’ers I know take some every day. Personally, I can’t get the stuff down!

      • leavemealonegoaway

        I have romaine salad almost daily. I toss it with AC vinegar before I make the salad, even if I add a different dressing..tastes great.

        • I have begun taking 450 mg apple cider vinegar capsules with each meal. Not sure if it will react the same way that regular apple cider vinegar does though. Dr. Fung, what is your opinion on this?

          • Hi Leftie,

            My husband started out with regular apple cider vinegar. Then switched to the pills because he hated the taste. But those were not as effective! So then we switched over to organic mother apple cider vinegar. The taste is better and the effectiveness was by far the best! We actually pour ourselves an 8 oz glass of water, add some soluble fiber and the vinegar and drink it down before every meal and 2 T of vinegar at bedtime. Works wonderfully!!

  13. Wenchypoo

    As a housewife, I can readily identify with the “freezer” part of your analogy and diagram.

    The other day, my doctor offered me a cookie from a batch another patient brought in to her. I said, “No thanks–gotta keep the insulin down.” she looked at me and said, “But you aren’t ON insulin!” I replied, “I know–and I want to stay that way.”

  14. Kathryn

    How would you modify this advice for a type 1 Diabetic, producing no insulin, with weight to lose? Modify their insulin dosages as low as possible gradually?

    • Hi Kathryn,
      I have heard of type 1s getting some type of relief from hflc.

    • KarenMarie

      You want to check out Dr Richard Bernstein. He’s a T1 diabetic and engineer and pioneered the use of the type of glucometer you can buy in any drugstore today. He left his engineering career and went to medical school so he would be taken seriously when advocating the tight glucose approach to managing T1 he was using for himself.

      His book is Dr Bernstein’s Diabetes Solution.

  15. Dr. Fung – first, thank you for the work you’re doing. You’re really opening people’s eyes to the true causes of obesity and how to fix things. Thank you!

    I have one question about the bariatric surgery. In this article and others you describe it as a version of fasting – but isn’t it really just forced caloric reduction? How does it give the benefit of not eating when the bariatric patient is still able to eat (albeit smaller amounts) constantly? I have always been confused by this. I would assume insulin would still remain high after this procedure if you are continuing to eat regularly but just less??

    Thanks again!

    • That’s a good question…..

    • Bariatric surgery results were the inspiration behind the Newcastle Diet according to Professor Roy Taylor. My personal experience on 600 calorien a day diet was one of weight loss and blood sugar levels falling to normal. Once you have done that it is easy to transition to full on fasting.

      • This may be your successful N=1 but a 600 calorie diet followed by full on fasting is a fast track way to getting an eating disorder. The starvation response after a 600 calorie diet pounces like a tiger that very few can resist. This is how many women, including myself, end up with bulimia or a binge eating disorder. IF is the buzz word now on the pro-ana sites as it becomes more and more acceptable to fast. A woman’s fitness site promoting purely IF has before/after pics of women and most were not even overweight, just healthy. As a person suffering the consequences of this people need to remember this is a hack for obese facing a diabetes gun barrel or people with diabetes. Anyone else needs to be aware of how they will live after the 600 calorie diet or fast.

        • Hi JW,
          Taking things slowly and seeing how you react to shorter periods of fasting and slowly increasing the length of your fasts should minimize the risk.
          Personally I did not experience a starvation response and it was not my first fast either, I had many shorter fasts of varying lengths under my belt before attempting that one.

    • Dr. Fung, PLEASE…. I would love some clarification on this. You describe Bariatric surgery, AND EveryOtherDay (<500 calorie=25% food reduction type Intermittent Fasting – as "fasting", and refer to Research involving those types of eating, as Proof of Fasting Benefits. But it seems quite CLEAR that Both of these Ways-of-Eating are REALLY simply forced caloric reduction to a very-low-caloric-food intake. … which is the same as Very-Low-Calorie-Restricted Diets. EOD research -Dr. Varady- said that further research had "surprisingly showed that eating small amount throughout the day provided the same intermittent "fasting" benefits as eating only 1 meal throughout the day. How does THIS type of eating (bariatric surgery-EOD type "fasting") give the same benefit of eating zero food when the bariatric patient, and IT person still eats (albeit smaller amounts) constantly? I admire you, Dr. Fung, and agree with most of your statements, but THIS ONE ISSUE really bothers me, as it seems so very Inaccurate and Contradictory. How can the use of research on Bariatric surgery diets & EOD eating 25% of TDEE requirements be considered to be Proof that "fasting" has more benefits than "low-calorie dieting" … when they are actually the same thing? Apparently for a great many people, insulin still drops when they are continuing to eat regularly throughout the day but just less food/calories?? I love your Blog and Book, but THIS is the Great Glaring Big Hole in this argument. I really wish you would clarify exactly what he means… because it is very confusing to me personally. I've read everything on your Blog, watched all your YouTube videos, listened to many of your podcasts, and purchased and read your book. Currently, I am working very hard to maintain a large weight loss. I was formerly morbidly obese.. without any type of diabetes….but have been maintaining a "normal" BMI for more than 10 years AND I had an RNY more than 20 years ago…(which forced me to eat small amounts of food several times a day – every day) , AND I have personally done quite a few years of experimentation with Intermittent Fasting (while eating small amounts of food on "fasting" days).

      • Please excuse typos in post above – no edit ability. A couple of the obvious errors were: “IT” meant “IF”, “he” meant “you”….etc. etc. etc.

      • ChicagoDoc

        Very reasonable questions and I don’t know that any one truly knows, but some possibilities:

        1. Bariatric surgery likely leads to major changes in the GI endocrine milieu (ghrelin, nutrient sensing in the small bowel, etc) in addition to the mechanical and caloric mechanisms which leads to weight loss and anorexia. How else could a patient endure daily starvation level calories , note that a significant amount of patients fail surgical efforts. In this sense it is not the same as fasting.
        2. It simply may not all be about insulin, if it was then LCHF diets would be expected to work far more frequently then they do, randomized trials show a very minimal advantage to low carb diets and experience shows that most will plateau prior to reaching goals.
        3. The concept of a weight set point is increasingly suggested and it may be that additional mechanisms are at work here to reduce the TDEE—microbiome, hypothalamic inflammation, food reward, genetics which operate outside insulin.
        4. All the described theories should be seen as a gestalt to understanding the remarkably complex physiology of energy partitioning and management rather than in a strict quantitative manner.

        I agree that the crux of the problem remains how to avoid reducing TDEE while also reducing calories. Fasting and exercise provide a useful framework in which to try do this in a manner which is different than the failed approach of moderate calorie restriction, I’m afraid we are just not at a point where strict, detailed explanations exist which can clarify the mechanisms involved. It sound like you are doing great and just realize that there are a whole lot more blanks to be filled in as regards this subject.

  16. Dr. Fung,
    I know that you say that extended fasts work quicker to reduce weight and insulin resistance, and that you have said that it is really up to each individual’s preference to decide what their fasting regimen will be, but as someone with a little weight to lose, and undoubtedly some insulin resistance I’d like to reverse, but no diabetes diagnosis, I am wondering what regimen I should aim for. I have been doing 23 hour fasts regularly, and I have tried a few 42 hour fasts (which have turned out to be rather effortless). Should I try to fast longer for any reason?

    Thank you for sharing all your wonderful knowledge!

  17. My metabolic nightmare started in the ICU. Steroids saved my life. But while in the hospital, they started giving me insulin. I started as an athlete and became gooey. Gained just under 100 pounds in 8 months. I did exactly what they told me. HCLF and mild cardio. Before I found Dr.Fung, I went back to my athletic routine. I am now intermittent fasting and LCHF eating. I have lost 30 pounds since January and have gone from 48%BF to 38% BF. I am off insulin and several other medications. I can not thank you enough.

  18. HeyPete

    Very informative post, as always. So on the subject of alternate day fasting being as effective as long fasts, 500-600 calorie on “fast” day does NOT “shut down” or slow our metabolism, is this why it still effective?

    • Yeah, what if we “fasted” by eating only 500 calories a day for several days?

      • HeyPete

        @Pam well that’s not very sustainable way to go about it, I know that much.

  19. Lastenia

    I am wondering how an HCG diet affects the metabolic rate? I really hope I haven’t messed it up for good. Do the hormones you take during HCG keep your Metabolism from dropping as it does with normal restricted calorie diets? I am starting IF and LCHF diet hoping to keep the weight off and increase metabolic rate. Does anyone know the answer??

  20. J. Emery

    Something bothers me, Dr.
    It’s confusing, because the Biggest Loser contestants also built substantially, increased muscle mass, the presence of which I associate with increased metabolism?
    Fasting vs 1200 calories.
    1200 calories is not enough for the body.
    Fasting is not enough calories for the body.
    The body recognizes that it needs to acquire energy from somewhere, because it isn’t enough, so we need energy to go kill an antelope.
    Fasting, it draws from fat stores more easily, and maintains or elevates metabolic rate.
    1200 calories, it does NOT draw from fat stores as easily, and it does NOT maintain or elevate metabolic rate.

    • High insulin levels vs low insulin levels while fasting, according to Dr Fung that’s the difference J. Emery.

  21. I am reading an article published by UHN News about an Epilepsy diet clinic at Toronto Western. Dr. E.D Bercovici advises patients to consume high-fat, low carb food options at Canada’s first adult epilepsy diet clinic. The clinic is designed to provide an alternative treatment path for htose with difficult to control epilepsy. “If what your doing now isn’t working try the opposite” that’s a quote from memory Doc.

  22. Soooo, does fasting work if I only consume say 500-600 calories a day from Coconut Milk in my Coffee in the AM? Or do we really need to get Calorie IN down to ZERO for the day?

    • Although true fasting is zero calories Professor Roy Taylor successfully treated patients with type 2 diabetes on a 800 calorie per day diet for 8 weeks, Called the Newcastle Diet. Six hundred of the calories were from sugary shake called optifast I think.
      In a recent post Dr Michael Moseley’s book shows you how to reverse diabetes on 800 calories per day using normal food. If you can go to zero calories it should speed up the process.

    • RCDAD,
      I was wondering the exact same thing.

  23. Hello Dr Fung,

    fellow Canadian here working in the middle east. I’ve been following your blog for several months and I’ve read I believe everything here. Curiously enough I find this to be very interesting. On top of that I’ve purchased your book for my kindle.

    I’m not overweight nor do I have diabetes. I work out consistently plus eat well.I’m within my ideal body, bmi and fat percentage is around 15 to 18.

    My issue is the tiny stubborn belly fat! How can I finally rid myself of that? I can fast 48 hours and 24 hours without a problem. Well, 48 hour fast is tough but doable.

    Which is better a 24 hour alternate day fast or a 48 hour fast once a week?


    • Try to do a very-low-carb, moderate-protein, high-fat diet… also check your circadian rhythm, have plenty of sleep and get your Vitamin D from sunlight – best time in ME is around 10am to 12noon, when your shadow is shorter than you.

  24. I have a question; If I’m able to reverse diabetes type 2 by fasting, eating less carbs etc. Will I have to keep doing this for the rest of my life, or could I re-introduce certain foods like rice and bread eventually BUT in small amounts and not too often?

    • Once you get into the habit of fasting then the occasional feast should be well tolerated indeed IMO necessary. When you eat those old foods you craved they will not taste as good as they tasted in your imagination and their hold on you will be broken.
      Your old cravings will be replaced by cravings for healthy food.

      If you deny yourself too much psychologically those old forbidden foods will eventually turn into overwhelming urges. Best to look forward to having them on occasion.

    • leavemealonegoaway

      William Banting discussed this in his 3rd Edition of ‘Letter on Corpulence’. He said he allowed himself some liberties, but kept an eye on things. If he noticed a drift in the wrong direction, he would get ‘strict’ again and pull things back. Sounds like a reasonable strategy.

    • N, I think it depends on what your tolerance for that stuff is. I’ve allowed myself high carb at times, even making my own sourdough bread with Einkorn wheat every month or so. Sometimes, like when traveling, it can be very difficult to eat a low carb diet, too. And I still like good pizza every once in a while. But I just fast after this, and then transition back to low carb.

      Personally, I’ve been low carbing for about 2.5 years and adding IF to that for about one year. It used to be that if I ate high carb for a few days, then for DAYS afterwards, I’d overeat, even eating low carb. However, this is getting better over time, especially if I add in fasting.

  25. As a person who has been overweight or obese for over 40 years, has dieted and lost — regained of course — I have a broken metabolism and insulin resistance. A few years ago I very strictly reduced my carbs to under 20 and was in strong ketosis for months, yet my weight loss was still stalled. I pretty much gave up because of the frustration of being so strict and not losing weight.

    This time, however, I’m still on the very low carb woe of eating, but I fast every other day for 22-23 hours. And it works! I am losing weight. I think this is a revelation for people like me who have been unable to access their own fat stores, no matter how few carbs. Assuming I get down to a normal weight (you just can’t believe it until it happens), I will have the tool of fasting available for maintenance. The hunger is much more manageable while in ketosis, and just drinking lots of water or broth actually works.

    This is a game-changer for those of us with chronic insulin resistance.

    • Kat, I totally agree with you.

    • Ahmad Luqman Alias Firdaus Bin Ab Patah

      Can we fix insulin resistant?

      How aboug your a1c?

      • At the very least you will get improvement but yes people have fixed insulin resistance and brought their a1c back to normal.

    • Kat,

      You are describing me exactly. It was a revelation to read Dr. Fung’s book. I too have dieted many times and regained. Eight or nine months ago I tried the LCHF diet. At first it was great, big initial weight loss and I actually enjoyed eating that way. But then….nothing for weeks and I got super frustrated figuring that LCHF might work for some people but obviously not for me. Reading Dr. Fung’s book has really opened my eyes and explained so much. I too would say that I have a broken metabolism and insulin resistance. I’m excited to hear that this is working for you as I just started IF about a week ago in combination with LCHF and I’m hoping that this is the answer for me. I’m doing alternate day fasting and have really not found it difficult at all. I know I could keep it up for as long as it takes as long as I’m seeing progress.

    • Good for you Kat. This gives us all more hope.

    • Can you give me an example of what you eat in one day please? I’m having some similar struggles.

    • Lisa Carroll

      Could you give an update and elaborate more; I have insulin resistance and tried everything. Just like you have become very frustrated and looking for SOMETHING….ANYTHING….that will work. LC

  26. Dear Dr Fung – thanks for this post which answers the questions I asked after reading your last post. I am a 54 year old man who has had weight problems on and off throughout my life, which I have gone to extreme lengths to overcome, but only with short term success. These recurrent weight loss efforts have no doubt left me with a low metabolic rate. I am now beginning to see great results by combining a lchf diet with 4 consecutive days fasting a week. This fasting regime, which will no doubt seem extreme to some, is only temporary, while I’m losing weight, after which I will probably go to 2 X 36 hours per week. However I should say that while not exactly effortless the 4 day fasts are doable, on top of working full time, albeit in a sedan try office job.

    I think the work you are doing in making sense of the scientific literature and translating it into effective programs and clear advice is amongst the most important work being done in the world today. Everybody else has only been offering partial advice, that ultimately has contributed to exacerbating the growing obesity crisis. If followed, your advice could literally save the world – and you aren’t even making any money out of it! You are literally a hero.

  27. Richard S Stone

    I want to add my comment to those many who happily point out that fasting is do-able, and it works. And not extreme multiple day fasts, but easy and manageable IF.

    My experience of what works is alternating days of not eating breakfast in the morning, which means waiting until noon or 1PM to have a breakfast (Why not have eggs and bacon then?), and then on the other days, skipping both breakfast and lunch and having any dinner you want. Hopefully, generally, a lchf dinner.

    Have coffee in the morning, but just black. Or tea without sugar. And without honey. Without anything… I know a lot of people seem to think they could not live unless they have sugar or some such thing with their coffee or tea in the morning, but no, you won’t die. You will live without the sugar etc. and be just fine. As far as I am concerned, fasting means not consuming any calories. It doesn’t mean only 400, or only 600.

    Part of this whole program is weaning yourself off of a child-like love of sugar, and becoming an adult, with adult tastes in food: I mean really, are we adults or five year olds?

    What does seem to be the case is that fat does not generate an insulin response. So insulin will not be triggered by fat in your coffee…. But why do that? Why even be in the kitchen dealing with food? Fat has the calories you do not want to consume if one objective of the program is weight loss, and your body will get those same fat calories from stored fat when you fast. Drink your coffee or tea, or plain water, and move on with life.

    • Actually, in Obesity Code, Dr Fung states having a little cream with coffee is acceptable. I was concerned over that issue as well. Certainly nothing wrong with drinking black coffee though. Just, if you hadn’t gotten Obesity Code, you might not realize coffee with a little cream is OK. For myself, I use 1 mini moo (10cal) and maybe a half oz of fat free. If we had 2% or whole milk, I’d bag the mini-moo but even at that I think the entire cost of coffee and creamer is like 20cal, not 400 or 600.

  28. Jennifer

    Hi there,
    How would you incorporate a vegan diet into this program?

    • Hi Jennifer,
      This is fasting Jennifer, when fasting all food intake stops, that’s it, does not matter what diet you are on, when breaking the fast just resume whatever diet you normally eat.

  29. “also known technically as ‘dropping dead’.” I’m still laughing!

  30. usually Dr. Fung has links to the articles he is discussing. does anybody know what article is mentioned above. i am referring to the table 2 graph and the jama 2012 mention. i usually look it up by author but neither is mentioned.

  31. I just read about scientists in norway finding a potential cure for type 2 diabetes using “appetite surpressing hormones” in diabetes medication. Does this therefore confirm that fasting also cures diabetes?

  32. Thank you Dr Fung. I viewed your six part series right before the NYT article came out. Hopefully you got a bump in OC sales and views of your 6 part series as I routinely gave shout-outs to both in the comments section of that NYT article. I have a problem now though.
    Jan2015 I retired from work after climbing to in excess of 300lbs, from 230 when I started 4 years earlier.Up to this point my fbs was fine always sub 100, ~85. In June2015 I was diagnosed NIDDM with an A1C of 8.5. With MFP in hand and a gym membership I sought to replicate the 2 month New Castle study. My subsequent A1C was 5.8 (yay!) My initial CER diet MFP set to -2lb/wk plus -3600/wk from gym seemed to pretty predictably float between 2.5 and 3lbs/wk, right up until it started to falter. Realizing MFP stopped dropping cal budget at 1500 I, armed with the BMR and Harris-Benedict, rode it down to 1250, when I decided to try to drop no lower than 1500 as I stopped dropping for no apparent reason (hadn’t seen vids or read book yet). While I always thought BMR was immutable, clearly it had become untethered from height, weight, age, sex. You vids and book also answered why. While I have not hit the rapid weight gain portion of the show my question is this. I understand CER (as Biggest Loser) will lower bmr and it will stay low even as weight regain occurs. Between Feb2015 and June2015 I had dropped 20lbs, I believe largely from a reduction in Cortizol generation so, perhaps, my BMR was lower than my, then, current weight and my body fought to lower my too high weight. However, between my reduced calorie budget and -3600/wk(gym) I lost, to date, about 80lbs. I think that represents a much greater than expected weight loss barring BL style regiment.

    Will starting the fasting regiment permanently return my bmr to match my weight or will that only occur while actively fasting? I still have another 30-40lbs I’d like to lose and I haven’t started the uncontrolled weight gain segment of the program. I’d also prefer my A1C go to the ‘never was diabetic’ range.
    thanks! And I continue to evangelize your book and 6part series.

  33. Just wondered how the “potato hack” as proposed by Tim Steele fits into the LCHF paradigm. As a matter of disclosure, I have no connection to the author and/or publisher. It is a 3-5 day very low fat fast of just eating potatoes. I try to do the “hack” once a month. I have found two results. 1. I lose weight. 2. It appears to “reset” my metabolism at the lower weight. After the “hack” I then go back to eating a no sugar-no grain Mediterranean diet, which ends up being fairly low carb. Obviously, the sample size is n=1. I know it works. I do not understand why. Thought this community might have some thoughts.

    • Thomas,

      Do you ever check your blood sugar when you do this? Just curious.

      • No. But your suggestion is good. Next time I try the potato hack, I will check blood sugar. Recent fbs around 80-85.

    • I have red somewhere that some fitness enthusiasts have one day a week with very high carbs and calories intake. This so called feeding day they say is for maintaining their leptin by tricking the body that there is more than enough energy (food) comming and the baby shouldn’t be “worried” and going into a “saving mode”.

    • I’m going to try the potato hack starting tomorrow. Thank you for posting this information or else I would not have known about it. Thank you again!

  34. Dr. Fung why do people such as Mark Sisson at Marks Daily Apple keep saying that women shouldn’t fast? Its confusing and getting really super annoying. I don’t know what to believe or who to believe anymore. The article I read was annoying. Made it sound like women are so much more delicate than men, which is annoying in of itself. I actually trust you more but I still feel confused about it. What the hell?

  35. Dr. Fung: I’ve been wondering about the evolutionary side of this for a while. I get that it doesn’t make sense for the body to reduce BMR when fasted, to enable hunting/food gathering. I also get that BMR is reduced when CI are reduced and insulin is high because the body can’t get to the fat stores. BUT: in the paleolithic setting, insulin was never high and Grok (to borrow Mark’s term) was always burning fat. Why then does it make evolutionary sense for the body to reduce calories when food was scarce but not non-existent? The need to be able to hunt/gather was there just the same.
    Or to put it differently: your argument is that BMR reduces because the body can’t get to the downstairs freezer. But when you are in ketosis, the downstairs freezer is always accessible, yet BMR still reduces on reduced CI. Why?

    • Hi mark, I believe the answer lies in the types of foods as well as the timing.. In “groks” time the foods that may have been scarcly consumed were not pumping out insulin like a modern snack food does. On top of that.. Grok was staring from a point of normality with regards to insulin sensitivity and not a damaged feedback system as many of us have developed over years of high PROCESSED food intake.

  36. Darrell

    Hello Dr. Fung. Great blog. As a backdrop, I have seen good success following a 16:8 IF protocol. Improved blood markers, weight loss, higher testosterone levels, etc. You have written about various forms of “metabolic resistance,” on numerous occasions. And that makes a lot of sense to me. Now, if we accept that such “resistance” can develop with consistent and high levels of exposure to certain things, such as insulin, antibiotics, alcohol, cocaine (heck, even the success of carb-refeeds is predicated on the same theory), can/will sustained exposure to a consistent and unchanging fasting protocol (even a successful one) elicit a similar “metabolic resistance?” In other words, would/could adoption of say, a 20:4 IF protocol for someone like me conceivably confer accretive benefits, in spite of my progress with my 16:8 IF protocol? Thanks.

  37. honeycomb

    Even Tom Hanks thinks he can reverse his T2D ..

    I hope he has been reading your work.

  38. […] 9. Fasting combined with a low carb, high fat diet effectively solves all of the above problems.  Studies show that fasting actually increases your metabolism. This is different from a low calorie diet, which decreases your metabolism. Presumably our pre-historic evolution mechanisms tell our bodies to go out and look for food. I mean, seriously, if your body was to shut down when you’re fasting, then you’d die! The ultimate goal of any species, from a scientific point of view, is survival and proliferation so why would mother nature set you up for failure?! Mother Nature is much smarter than we give her credit for. […]

  39. I believe there is something fundamental I am missing. In principal I understand the 2 compartment analogy. However, on the 24 hour fast regiment how does the body ever transition to burning fat? From Obesity Code (p.239), the body does not transition to that mode, ketosis or even Gluconeogenesis, until after 24 hours of fasting. However, one resumes eating at that point. So, wouldn’t that mean the patient oscillates between feeding and the post-absorptive phase? I believe I am correct in assuming the stored glycogen in the liver is exhausted in the time between finishing the evening mean and the start of the evening meal the following day. In that intervening time, insulin levels drop to zero. When does the fat, especially waist and pancreatic fat get consumed in the alternate day fasting?

    Just as an aside, which may or may not be relevant, I have been doing a repeating day 1 of the 24 hour fast cycle. This means I have one meal per day, eating between 5pm and 8pm.
    From p.252, where I am staying on the Monday diet, not transitioning to 3 meals is this considered intermittent fasting as I do have a meal such as, swordfish steak plus large salad w/oil and vinegar dressing. So technically, would I be on a 20hr fast?


    • I believe there is something fundamental I am missing. In principal I understand the 2 compartment analogy. However, on the 24 hour fast regiment how does the body ever transition to burning fat? From Obesity Code (p.239), the body does not transition to that mode, ketosis or even Gluconeogenesis, until after 24 hours of fasting. However, one resumes eating at that point. So, wouldn’t that mean the patient oscillates between feeding and the post-absorptive phase? I believe I am correct in assuming the stored glycogen in the liver is exhausted in the time between finishing the evening mean and the start of the evening meal the following day. In that intervening time, insulin levels drop to zero. When does the fat, especially waist and pancreatic fat get consumed in the alternate day fasting?

      Just as an aside, which may or may not be relevant, I have been doing a repeating day 1 of the 24 hour fast cycle. This means I have one meal per day, eating between 5pm and 8pm.
      From p.252, where I am staying on the Monday diet, not transitioning to 3 meals is this considered intermittent fasting as I do have a meal such as, swordfish steak plus large salad w/oil and vinegar dressing. So technically, would I be on a 20hr fast?


      • I had been using an incorrect email address which this last (repeat) post corrects.

  40. Margaret

    “If your reduce your calories from 2000 to 1200 per day, then your body is forced to reduce calorie expenditure to 1200 per day since it cannot get any from the stored food (fat).”

    Look, I agree with everything about LCHF, ketogenic diet, fasting etc., and I know calories in/calories out is nonsense, but this can not be completely accurate. If the body on a reduced calorie, SAD diet can’t get ANY calories from stored fat, then how does anyone lose weight this way? People DO lose weight at first on biggest loser/weight watchers crap diets and it can’t all be muscle or they would be unable to move after a while!

    • Yes Margaret as you say yourself people DO lose weight at first. My understanding is that the body slowly adapts to “living within its means” When this happens weight loss stalls. As your insulin levels stay high so does your hunger,food is always on your mind. It takes a special sort of sadist to enjoy losing weight this way.

      From personal experience it is a pretty miserable way to try and lose weight. When you do give in eventually you end up heavier than when you started.

      Many more people find it easier to stick to lchf than lfhc.

      However not everybody is the same and a few people have had success with lfhc. Before lchf these few would make everybody else feel bad for not sticking with the program.

  41. This is, by far, the best article I’ve read. Tt explains things in laymen’s terms. Thank God! I’ve been doing Keto for a year & have taken the advice from all the guru’s (Jimmy Moore, Stephanie Person, Jacob Wilson, Dominic D’Agostino) & many others. What I would like to know is what to do when “physiological insulin resistance” resulting from LCHF or Keto & Fasting Blood Glucose rises over 100 (upwards to 115) & post prandial or post meal values are higher than that. Keeping a calorie deficit is what we’ve all been taught as far as we can all remember. It’s such a paradigm shift to believe that if my basal metabolic rate BMR is 1500 calories a day, that if I take in 1500 to 2000 calories a day (80% of it being fat, 15% being protein, & 5% being carbs), that calories in, calories out won’t apply, even if do HIIT & Resistance Train 1 hour a day, 4 days a week. That’s mind boggling & I’m still trying to wrap my brain around that. What exactly happens when you take in more LCHF calories than our bodie’s burn in a day? I love your articles & hope to read more that address these concerns. God Bless!

  42. I’m not a diabetic by any means, however, over the past year, while on Keto, I’ve seen a slow rise in fasting blood glucose while keeping my macros on point. They started out under 80 & have progressively gotten higher. My blood ketones are usually between 1 & 3 mmol/s. I’ve read a lot about Gluconeogenesis, Dawns Phenomenon, Physiological Insulin Resistance (the kind that’s not related to diabetes). I’ve intermittent fasted before too. It’s very easy to fast on Keto because hunger is so easily controlled. I’ve done a 16 hour fast with an 8 hour eating window days in a row with no problem. I’ve thought about going 20/4, but how could I get 2000 LCHF moderate protein calories in 4 hours with a BMR of 1500 & not gain weight? I guess I’d like you to touch on these things again in another article & at the same time, incorporate your insulin findings & communicate them in the simple way that you do. Thanks so much for everything. God Bless!

  43. Hi. Thanks so much! very interesting stuff. What I don’t get (and I think others are saying similar things above) is what the fundamental difference is between intermittent fasting, and restricted calories, as far as combating the lowered set-point. Why does bariatric surgery (which is forced reduced caloric intake) not (supposedly) affect the RMR long term, whereas a restricted “biggest Loser” diet does? Could it be that the intermittent fasting diet completely lower insulin or the glycogen while a regular restricted diet doesn’t? And if so, then there would need to be some guidelines as to how long a fast does this, and what exactly is needed in between so as to offset the triggering of a lowered RMR, but not refill the refrigerator or raise insulin too much. I hope I am not sounding nonsensical. If you could write a clear post about this, it would answer a lot of questions.
    Thanks again!

  44. Hello Dr. Jason Fung or anyone who can answer.

    I am an obese person, because I went from 127 kg to 105 with Lowcarb diet and now with fasting, my intention is to lose more weight.

    I was fasting every other day but with time spent doing daily from Monday to Friday, leaving as few free Saturday and Sunday.

      I have the following question: do fast 23: 1 with power around 1000 calories, this form of fasting can harm me in losing weight?

    Thank you!!

  45. Kamran Karimullah

    Dear Dr. Fung,
    I have read your excellent articles (and the links in them) on the potential benefits of adopting a low carb diet to help manage T1D. It seems that, at least in theory, a person with T1D on a low-carb diet could benefit from using a fasting regimen as well. I am very keen to hear if there are Type-1 diabetics who have any experience in practicing this type of regimen. I am particularly interested in insights into the duration of the fast, how to maintain regular glucose levels throughout the day (and night).

    Finally, when I was diagnosed with diabetes 20 years ago or so, I was of course taught that ketogenesis is an intrinsic evil. I am convinced that what I was taught was not true. My fear however is that a fasting regime for a person with T1D could begin the process that leads to ketonacidosis, even if the person is euglycemic. Is there a minimum amount of insulin that needs to be taken that ensures that the body with T1D does not start down that dangerous road?

    Thank you.

  46. Hey everyone, Im a bit late to the party but hopefully someone will still see this and might be able to answer. I was wondering if there are studies on the effects of Alternate Day Fasting that lasted longer than the one Dr. Fung shows (22 days), especially does the RMR decrease over a longer period of time – the 22 day study shows a minimal decrease. Wondering if that would change in the long run.

    Im also curious what the study would show for a shorter fast, for example 20/4, would it also stop the RMR to drop due to calorie deficit?

    If anyone could help answer these questions, it would be much appreciated.

  47. Roger Bird

    (sarcasm) It is amazing that there are so many lazy people among the contestants, and yet they worked so hard to win. (/sarcasm)

  48. I am very interested to find out if there is a connection between hypothyroid disease and insulin resistance and if insulin resistance could be largely responsible for the thyroid dysfunction. It seems coincidental that many of the symptoms of hypothroidism are so parallel to insulin resistance symptoms that are described in this blog and if a fasting protocol could help

  49. Is there a way to at home to monitor our insulin levels? I am completely buying the idea of the fasting, but it would be great validation of a person’s fast if we could track the levels. Like maybe a 24 hour fast is 20% better than 20 hours, etc. Or some other way to find the best amount of fasting time for the individual.

    • Yeah you can buy a home blood glucose monitor kit. You can get them at Walmart or on Amazon. If you’re not diabetic, then insurance won’t cover it but it’s not too expensive ($30-50) for the better ones, even cheaper for some. But there is the ongoing expense of replacement test strips also. How it works is: you prick your finger with a lancet and a bead of blood appears which you put on the test strip and then feed the strip into the glucose meter. It gives you a fairly accurate reading but even if it’s not super accurate, you’d be looking to see a trend over time or with various time increments of fasting. Be careful though, I caused myself a diabetes scare by doing this and had to go to my doc for a lab glucose and A1C test to reassure myself that I’m not diabetic or pre-diabetic, since the random numbers coming out of the home meter scared me.

  50. Fasting and starvation are two separate issues. I built up a fasting regime and managed longer and longer fasts. I always felt healthy on these fasts, with a lot of niggly small health issues going away. My eyesight, skin, energy levels, occasional heart palpatations, and many other minor negatives, improved or disappeared completely. On one fast, way back, of 21 days, toward the end, say last few days (maybe a week) I started sprinting a 100m, many times a day, I felt so good and full of energy.

    I fasted for the whole of Feb 2004, no food, only water with a little salt and squeeze of lemon juice. It was the best and gave me a most wonderful spiritual experience/feeling I will never forget.

    After 2004, I didn’t get to fast for ten yrs or more, all the time wanting to do another. Eventually I decided and managed to fast again, somewhat apprehensive of the effect of not fasting for so long. This last Feb 2016, the whole month. On this fast I did however have a couple of (2 or 3) bitter almonds a day for about half of it. I also experimented with a little bicarb of soda and sea salt in the water I drank. All the usual benefits occured.
    There is a rebound weight gain but that adjusts itself and you end up back where you started. I did not fast to lose weight only/exactly – I also wanted to feel the amazing clarity, health, etc.. I believe long term health is improved, for instance, arteries. Although I could not see the condition of my arteries and plaques therein, judging by the other issues that improved, I am confident that a lot of invisible good took place. I will be disciplining myself to fast more regularly, like one a year – an extended fast – at least a month. I think I can go longer. I try to listen to my body when fasting as it is said that your body tells you when the fast is over – after that, if you keep going, you are starving yourself. It takes a lot of faith that you are doing the right thing, that fasting is OK and not just OK but one of the best healing practices ever. All that I’ve read, admittedly old physician books of the alternative physician of 1800, 1900s, talked of the benefits of fasting and gave many real patient evidence and experimentation of a sort. They did some great work, I’d recommend anyone to read those. I relied on these to reassure myself that I wasn’t injuring my health, sustaining untold irreversible damage to my organs, etc., etc.. I am confident in this practice and proved it to myself and thus anyone prepared to believe me and try this themselves. I’m sure it will benefit all human beings to do this – although timing might be important and paradoxically some may be too ill to do it. There are some circumstances where fasting would not be recommended, others where other treatment, cures would be needed before a fast may be undertaken. I would like to say/disclaim by saying consult a medical doctor for advice or supervision of the fast, but in general it seems most in the medical profession haven’t a clue. Most doctors would say you are crazy to fast for a week, let alone a month. You would have to find the right doctor or be strong and decide for yourself, do it and just let common sense guide the rest. I, for instance, took my blood pressure every day, sometimes two or three times. On a fast you will feel light headed if you rise from sitting too fast, for instance. My blood pressure dropped to around 95/65. It is normally a little under the average anyway, like 110/70. I think this is a good indicator of how you are doing, once fasting, to have a steady state after a short while.
    I am 54 this year and started fasting when I was around 33
    For what it is worth, I share my experience/experiment.

    I recently found a reference to Zoe Harcombe web site about the Minnesota Starvation Expt and posted the above account there. Zoe responded to my post immediately and suggested I look at this site about fasting, gave me a link. So, just in case, readers here don’t know of that site and comments, I have posted the same comment here. I hope that is acceptable.

  51. I would love to cure my father’s diabetes. He is a wreck. I tried giving him vinegar in water before meals and he now is refusing to drink it! Weird because I actually like it and drink it myself. So I was wondering if anyone knows if kombucha would work as well? I know kombucha is slightly sweet and contains some sugars so is not as good as ACV. Anyone tried it or know of any studies of this or have an opinion?

  52. hey ,
    I have a question, if you are diabetic or prediabetic, howlong should do these fasting ? do we need to continue the same life long?

  53. […] How to Fix your Broken Metabolism by doing the Exact … – We saw last week with the Biggest Loser study that basal metabolism plummets when you lose weight with calorie reduction. As contestants lose weight, they burn a lot … […]

  54. Dr Fung: I am confused. At one point in your article you say: Four consecutive days of fasting increases basal metabolism by 13%. Then in the next paragraph you say that basal metabolism was maintained over 22 days of ADF.
    So does this mean that if you want to rev up your metabolism you need to do extended fasting for multiple days?
    After 50 years of yoyo dieting I am sure I have wrecked my metabolism. It looks like the best way for me to fix it is to fast for 4 days at a time.

  55. Ozgur Baydemir


    there’s one thing i could not understand in full.
    i got it. we’ll fast as long, to keep the the insulin levels as low.
    but if we go on a caloric deficit, our metabolism will respond by slowing down. so the calories in and calories out will be equal and we won’t be in a caloric deficit.
    so how will we loose fat ? just by workout/cardio/move more ?
    or should we do what ??

    • Read the posts! Especially the April 5, 2015 that states,
      “I spent over a year and 60+ blog posts, and 8 hours of YouTube lectures explaining why diets that reduce insulin (particularly a Low Carb, High Fat diet) are an integral part of a weight reducing strategy. Also despite the fact that I use LCHF in the IDM clinic on literally hundreds of patients with type 2 diabetes. However, my point is this. Obesity is a multi-factorial disease, as I previously wrote about. This means, that there must be multiple targets in the pathway to obesity. A LCHF diet, for some people will be sufficient for weight loss. Many do extremely well. But we cannot ignore those for whom LCHF is not enough.” The other strategy of weight loss is FASTING.

  56. Ozgur Baydemir

    so guys…noone answers ??

    • It appears that way to me, too. Which is unfortunate, because there are some very good questions here that if answered, would really help clarify things. :/

Leave a Reply