Fasting Regimens – Part 6

posted in: Fasting, Health and Nutrition | 108

There are many different fasting regimens. Let’s be very clear to start, though. There is simply no ‘best’ one. They all work to different degrees for different people. Just as some people prefer steak to chicken, there is no right or wrong answer. One regimen will work for one person but be utterly ineffective in the next.

Martin Berkhan
Martin Berkhan

Fasting is defined as the voluntary act of withholding food for a specific period of time. Non-caloric drinks such as water and tea are permitted. An absolute fast refers to the withholding of both food and drink. This may be done for religious purposes, such as during Ramadan in the Muslim tradition, but is not generally recommended for health purposes because of the accompanying dehydration. In our IDM program, we do not ever use the absolute fast.

Fasting has no standard duration. Fasts can range from twelve hours to three months or more. You can fast once a week or once a month or once a year. Intermittent fasting involves fasting for shorter periods of time on a regular basis. Shorter fasts are generally done more frequently. Longer fasts are typically twenty-four to thirty-six hours, done two to three times per week. Prolonged fasting may range from one week to one month.

I categorized fasting periods with a break point at 24 hours, although this is somewhat arbitrary. In my experience in the IDM program, I generally use shorter regimens for those who are mostly interested in losing weight without much in the way of type 2 diabetes, fatty liver or other metabolic diseases.

For those who have more significant illnesses, I use longer duration regimens as they tend to give faster results. After the initial ‘breaking’ in period, we always work with the patients to find out what they prefer to do. A surprising number of patients prefer longer duration fasts less frequently.

Short Daily Fasting Regimens

1. 12 hour fasting – There are several regimens of fasting that use a shorter period of fasting but done every day. A 12 hour fasting period done every day used to be ‘normal’. That is, you would eat 3 meals a day from, say 7 am to 7 pm and refrain from eating anything from 7 pm to 7 am.TedNaiman1

At that point, you would ‘break your fast’ with a small breakfast. This was pretty standard in the 1950s and 1960s. There wasn’t much obesity back then. However, there were two major changes that happened since then. First was the change to a higher carbohydrate, lower fat diet. This tended to increase insulin. Second was the increase in meal frequency, as we detail in a previous post, which tended to reduce fasting periods.

If you could eat unprocessed foods, avoid excessive added sugars, and did not have significant insulin resistance to start, this 12 hr daily fasting was probably good enough for most people to avoid obesity. However, it is not really strong enough to reverse decades of insulin resistance.

2. 16 hour fasting – This regimen involves using a daily 16 hour period of fasting and an 8 hour ‘eating window’. For example, this would mean eating from 11 am – 7 pm, and fasting from 7 pm to 11am. This generally means skipping the morning meal every day. Some people choose to eat 2 meals during that 8 hour window and others will eat 3.

This regimen was popularized by a bodybuilder by the name of Martin Berkhan who blogged about it on his website, and so the method is sometimes called the LeanGains method. He wrote extensively in the years 2007-2010 but I don’t see much activity on his blog anymore, which is a real shame, because he had some great ideas and original thought. There are still some excellent posts there.

He wrote extensively about training in the fasted state and eating predominantly in the post-workout period. These ideas are supported by the science available (albeit not a lot). However, they do make a lot of common sense.TedNaiman2

Several years later, an editor at Men’s Health wrote a book called The 8 hour diet, which essentially used the same 8 hour eating window as the LeanGains method. In his entire book, he strenuously avoided any mention of LeanGains or Berkhans, even though this method transparently ripped-off LeanGains. You can’t really patent a time period of fasting, but the intellectual dishonestly was appalling, regardless. It is like writing about E=MC2 and never mentioning Albert Einstein, but instead pretending to have ‘discovered’ it yourself.

3. The ‘Warrior’ diet – This was one of the first diets to popularize intermittent fasting regimens. Written by Ori Hofmekler in 2002, this diet stressed that timing of meals mattered almost as much as composition of meals. In other words, ‘when you eat makes what you eat important’. Actually, I think both are important, but the ‘when’ question is seriously under-appreciated, and this book was one of the first to really point this out.TedNaiman3

Drawing upon inspiration from ancient warrior tribes such as the Spartans and Romans, the core of the diet consists of eating all meals in the evening during a 4 hour window. The fasting period of 20 hours consisted of most of the day. There was also an emphasis on natural unprocessed foods and  high intensity training.

The main point of all these fasting regimens is the same. It allows the body to lower insulin levels very low for a specified period of time longer than usual. This is precisely what helps to break, or prevent the development of insulin resistance. As we’ve mentioned previously, this is the fundamental biologic principle of homeostasis.

The body likes to maintain everything within a relatively narrow range. Any prolonged stimulus leads to resistance as the body tries to resist the change. In this case, prolonged periods of high insulin will lead to insulin resistance, which will lead back to high insulin levels – in other words, insulin causes insulin resistance.

So, by incorporating daily, or almost daily periods of low insulin, we are able to prevent the development of insulin resistance and even reverse relatively minor levels of resistance. For more established resistance, we would need longer fasting periods – 24 hours or greater.

One of the key advantages of fasting, from a therapeutic standpoint is the lack of upper limit. What this means is that we can continue to apply fasting in an almost unlimited manner with no upper ceiling. The world record for fasting was 382 days, during which the patient suffered no ill effects.

Think about medications for a second. If you take metformin – there is a maximum dose. Same for virtually all meds. Think about low carb or low fat diets – you can only go to zero carbs or fat. There is a maximum dose. That is why insulin is so popular with doctors. You can keep increasing the dose with no ceiling. (As an aside, we recently had a lady taking 400 units of insulin per day in our clinic. Her endocrinologist was happy that her sugars were ‘finally’ controlled. I was appalled.)

Fasting, similarly has no ceiling, which offers much more therapeutic flexibility. In other words, if I can keep applying fasting until I see the desired effect. The dose can go up indefinitely. If you don’t eat, will you lose weight? Of course. So there is almost no question of efficacy. It is only a question of safety and compliance. So for more complicated or serious cases, we can simply increase the dose. We will consider these longer regimens in the next post.

A big thank you to my friend Dr. Ted Naiman who created these graphs.

Start with Fasting part I

Continue with Fasting part 7

108 Responses

  1. Victoria

    Or like writing about E=MC^2 and never mentioning James Clerk Maxwell.

    • Simon Thompson

      Ha Ha Victoria- Beat me to the punch! Warrior diet looks really good- and is what I have gravitated towards.

      • kurtdriver

        Hofmekler quotes Edgar Cayce on nutrition, which is rather odd, to say the least.

    • David Spector

      Maxwell’s equations do not include e=mc**2, which was discovered by Einstein later, in 1905. Maxwell was dead by then. Just saying.

  2. Richard Quinn

    Thank you Dr. Fung, very useful information.

    I have read that fasting can increase serum uric acid concentration, as a byproduct of increased cellular degradation. Have you seen this in practice amongst patients with preexisting hyperuricemia?


    • Yes, there is at least one study that shows this effect, and it may be due to mild volume depletion. While the uric acid may increase, I have not seen an increase in gout, although this is only my personal experience and can’t say for sure that it will not happen.

  3. Thank you so much, Dr. Fung, for this invaluable information & for your whole blog!!!!!! It is revolutionary & precious information!!!!!!!!

  4. Bernard P.

    Dr. Fung, one of these days you should tell how you came to doubt the standard mainstream diagnosis and treatments for diabetes; how you found out about high blood glucose being a symptom of insulin resistance, and not “diabetes”; and how fasting came into the picture as a treatment.

    Maybe this will be part of your upcoming book.

  5. From what I remember about the “Warrior Diet,” I thought the under-eating phase might have contained eating that would not comply with an actual fast. I like the 20:4 timing though, have found that not to be a problem. I am curious and will have to find my materials on the “Warrior Diet” and see how it fits in with my current thinking, it’s been about a year since I read his book. Does anyone else have an opinion, observation?

    I am a 71 yr old healthy male, and have been on a sugar free nourishing traditions diet for the last couple of years with no insulin or weight issues. I have chronic sinusitis, occasional mild reflux, and a chronic coated tongue. I commenced your fasting regime last week with one 24 hour fast and continue with the 12 hour (no breakfast, no grazing between meals) daily fast.

    Your comments earlier on autophagy cause me to wonder if you have any experience showing that fasting may help my sinusitis. I am already noticing less reflux, and the tongue coating is gradually receding. I plan to keep the regime up regardless, but am very interested in your perspective and comments.

    • Many people notice less reflux, for sure. I haven’t heard much about tongue coating, but my guess is, as yours, that autophagy is being activated.

    • Great news Mr Spanier! I too have had reflux and sinusitis (the coated tongue also before I quit sugars). I eliminated all grains and settled on organic vegetables and bone broth, raw salads with avocados, lightly cooked pastured eggs, mackerel, grass-fed butter, coconut oil and e.v. Olive oil. The reflux has abated and my sinus is clear. My head seems less foggy and my sleep is more sound. On the odd occasions that I’ve been ‘out’ to dinner and indulged on paella or the like, I’ve been tormented by reflux that night and over the next few days. Red wine set it erupting also, sadly. I was just wondering if it could be grains that your body is not dealing with. All the best to you and your health.

    • For what it’s worth, and this was just my personal experience, I found taking one tablespoon of Bob’s Red Mill raw potato starch—which is extremely economical—per day, stirred in with water, caused enough changes in my gut microbiome that my acid reflux went away (I was previously taking ranitidine from 300-600 mg/day, which is a very large dose) (speaking of dose, if you try the raw potato starch and/or amla suggested below, I’d start with a dose of no more than a third of the target dose, and slowly work your way up over a few weeks, since your body’s microbiome has to adjust to fully use the new nutrients).

      Many people have reported similar results, although, of course, not everybody. A website called “Free the Animal” has many articles on this, and Chris Kressler’s website has a few too. I don’t think it’s a panacea, but it seems to have helped a lot of people rid themselves of acid reflux in particular.

      Now I mix up my “prebiotic” sources and take other prebiotics as well: sometimes Bob’s Red Mill raw potato starch (found in many grocery stores or easily online), sometimes inulin (found in most drug stores), etc. Some people take larger doses, but I found a tablespoon was enough for me, and, with inulin, perhaps even a little less.

      In point of fact regarding how little is required to have a disproportionate beneficial effect, I also take a teaspoon of dry amla powder aka Indian Gooseberry, which is the premier herb used in traditional Indian medicine. It is also inexpensive!

      Amla has some soluble fiber and, like inulin, it is sometimes prescribed by herbal practitioners for constipation. It changes the microbiome as well because it’s a rich source of polyphenols and soluble fibre, both of which are important sources of food for gut bacteria, aka prebiotics.

      However, when antioxidant analyses were done, amla fruit was shown to be the most micronutrient-dense fruit known to mankind—far more than, say, blueberries or goji berries (both of which are still good). I can’t help but think its micronutrient density is a major reason why it gained such a prominent place in Indian medicine with a reputation for effectiveness. Note that India has lower cancer rates, lower diabetes rates, etc., and its spice and herbal-medicine culture likely plays a major role in this.

      For a person on a LCHF diet in particular, it may be a real benefit to get a few low-carb (the “resistant starch” is starch that is mostly not ingested by humans, and that’s why it’s a good prebiotic for bacteria: the bacteria themselves ingest it, it changes the ratios of types of bacteria in the gut, and the bacteria produce useful substances in our guts such as butyric acid) additional sources of resistant starch, fiber, and especially micronutrients … but also be aware that the dose makes the poison, and I’m not suggesting you go nuts with huge amounts of prebiotics or amla powder.

      In fact, here’s a study showing that half a teaspoon to just one teaspoon of amla per day reduced blood glucose more than a leading diabetes drug—without side effects. How do you like ’dem apples?

      It also seems to help reduce incidence of cancer; resistant starch, fiber, and polyphenols also help to reduce insulin somewhat, so should fit in right in with Dr. Fung’s philosophy, but that’s just my interpretation and opinion: he can certainly correct me if he disagrees.

      Are these few food-based supplements powerful enough to overcome a terrible diet? I’m sure they’re not. For their tiny economic cost, do they do a lot of good? I think so—especially for those not eating a whole-food plant-based diet which, realistically, already has a lot of these micronutrients.

  7. Great post!

    A few points:

    • Totally right about 8-Hour Diet, which I own, being an uncredited rip-off of Lean Gains. That’s regrettable, which isn’t to say it isn’t a good book (albeit written in a breathless tone).

    • My understanding is The Warrior Diet allows some food during the day, so it isn’t really a total fast. It allows some raw vegetables and fruit and a little soup. It also claims humans are naturally “night eaters” with some dubious or at least cherry-picked references for that. In any case, we’re not naturally “all-day, all-night, all-the-time” eaters. This modern, destructive eating pattern was probably exacerbated by electric lighting—in fact and contra The Warrior Diet’s premise—leading to more eating at night as well as some direct adverse hormonal effects to do with melatonin and reduced sleep per se causing significant short-term, reversible insulin resistance.

    • As for whether exercise should be done before or after eating, that is an interesting point and something I don’t know about one way or the other. Lean Gains and 8-Hour Diet come down on exercise before eating, although the latter only cites one small study in support of it. Many other studies show enormous benefit to blood glucose control derived from exercising within up to two hours after eating, but minimal benefit to blood glucose control (at least directly) if exercising before eating. Any exercise-mediated benefit to blood glucose control is gained without needing either more exogenous or endogenous insulin, or oral antidiabetes drugs; so this could be a rather remarkable benefit which we should not too quickly dismiss. It may well be worth integrating post-meal exercise into one’s lifestyle (which should be easier for intermittent fasters consuming an average of, say, only two meals per day!). Arguably, one could gain all the important fitness benefits of exercise plus improved blood glucose control in the time otherwise wasted unproductively testing blood glucose pre- and post-eating, injecting insulin, taking insulogenic oral antidiabetic drugs of dubious benefit, etc.

    “(As an aside, we recently had a lady taking 400 units of insulin per day in our clinic. Her endocrinologist was happy that her sugars were ‘finally’ controlled. I was appalled.)—Jason Fung, MD”  ¶  I have had little interaction with them, but looking at how they look at insulin and diabetes (and their utterly ineffective regimes for same), I am extremely disappointed in endocrinologists. There may be some hormone systems they have a grasp on and can give useful prescriptions for, but here they seem to ignore the downsides of excess insulin (increased tolerance and forcing more calories into the fat cells, mainly) … and focus on surrogate markers rather than important, life-impacting health endpoints. It makes me question their intelligence, frankly.

    • I’m not claiming this is the be all or end all protocol, but I’m finding this is working psychologically for me, makes sense from a time management perspective, and provides not only beneficial fasting stresses, but a certain element of pseudo-randomness which may better emulate our fluctuating energy intake in our ancestral environment. What I’m currently doing is:

    Towards the end of the day and toward the beginning of the day, fast intermittently; and, once per week, fast for a day.

    In other words, I’m combining daily intermittent fasting by delaying breakfast until I am well and truly hungry and also not eating particularly late in the day, at least most days … with a longer, weekly 24-hour fast. In reality, that longer, weekly fast is sometimes extended beyond 24 hours because of combining with the variable daily fasts. I’m finding that this mixture of these two protocols, one quite flexible in terms of timing, easily fits in with one’s lifestyle, yet hopefully provides the benefits of both shorter and longer fasts; this comes about either because I’m not so hungry that I need to eat at the end of 24 hours or because it isn’t convenient for me to eat at that time due to the time of day or my location, etc.

    The shorter fasts are more frequent than the longer fasts, which makes sense. So some days may have only a 12-hour fast, others may have a 19-hour fast, and still others a full 24+ hour fast: once per week, counting the overnight portion. It works for me. You might find it works for you too if you’re not sure of which of these regimens to integrate into your lifestyle.

    Purposely integrate a couple fasting protocols for additional flexibility and varying fasting eustresses.

    • Finally, there is a free e-Book called Fast-5 that you may want to review and mention. It was designed by a medical doctor named Bert Herring (there’s also a TED-x speech given by him) and is simply a 5-hour eating window with a 19-hour true fast-from-food each day. It may be worth reading simply because it’s free and has some good information and inspiration in it.

    Similarly, there are Facebook Groups for this and other fasting protocols you may wish to join, as I have, for additional support and tips.

    I really appreciated this post showing all these different, great options for fasting that can fit into our lifestyles now and as they change in the future!

  8. Thank you Jason Fung for this great blog & lectures.
    People who are insulin resistant and suffers from depression, anxiety and/or fibromyalgia, will their metabolism require a longer period to adapt to a LCHF diet and a fasting regimen?
    Should they espect initial worsening of mood, agitation and/or pain?
    Or should they stay away from LCHF and fasting?

    • The effect on depression and anxiety is variable. Some feel better, others not. I have not found it to be particularly useful in fibromyalgia. There is still no reason to avoid LCHF.


        I have been doing LCHF and intermittent fasting for 2 years now. I am in nutritional ketosis most of the time. I was of normal weight but suffered from what was diagnosed as fibromyalgia after contracting the Parvo virus for 16 years. I am symptom free since I adopted this lifestyle. I do full body resistance training 3 times a week, run sprints once a week and do a steady state cardio workout once a week as well. I am 52 and female. I would definitely give it a good try.

    • If doing LCHF (or any other diet) for depression, I’d heed at least this one aspect of the diet advice of WebMD to help with depression and try to make your diet as micronutrient-rich as possible (so your few carbohydrate foods would be micronutrient-dense, such as green veggies, other colorful veggies, and berries rather than, say, white rice or sugar … less-processed meats and other animal foods rather than, say, cold cuts). Micronutrients mediate (in this case, reduce) inflammation, which has been implicated in depression. Dr. Kelly Brogan is a psychiatrist who both believes inflammation is important for treating depression and that a lower-carb diet can help. I personally am following a plant-based diet, but I’m sure we can all agree that the more nutritious the diet is per calorie, the better.

      Of course, excess insulin is implicated in inflammation too, so fasting can be beneficial.

      Good luck, Nina!

      • Correction: I meant, “inflammation is important for understanding depression,” of course, not for “treating” depression. Reducing systemic inflammation is likely to be an important part of treating depression.

    • Danielle

      I have been eating almost zero carb (no plant foods, with a little full-fat cheese making up the majority of my small carb allowance) for year now and whilst I am no doctor, my chronic, severe depression (which left me with peaks of suicidal thoughts and long, snowballing phases of despondency) literally ‘cleared up’.

      I am not suggesting low carb cured it by any means, but there is definitely some correlation on carbs/sugars especially and mental health. My moods stabilised, those spikes of severity vanished, all the depression-related aches and pains went away, I slept like a baby and I no longer randomly cried or felt angry. I felt so good.

  9. I started eating two meals per day, between 9 and 5 and not eating between 5 and 9 about two years ago. My weight is steady and there is no energy shortage, or ups and downs. In fact, what I was really interested in was the effect when riding my bicycle 50 or 60 miles during the day. I used to drink and eat the usual high-carb biker garbage. Surprisingly, after the change there was no problem at all. I did not eat, but drank water when thirsty. I am 68 years old, and my diet is running about 75% fat from animal sources. I wish I had figured this out 30 years ago.

    My guess is that anyone on a high carb diet is going to experience problems initially when fasting and athletic performance will take some adaptation. However, once you make the transition you don’t want to go back.

  10. Dr. Fung – Thank you for this excellent series. I try to fast 12-16 hours daily; however, I usually have a couple of cups of coffee with cream each morning. Will the coffee with cream reduce or negate the positive effects of fasting? In other words, does the small amount of fat calories in the cream break the fast?

    • Hi EJ,

      I hope you’ll forgive me for offering this link. I don’t mean that Dr. Fung shouldn’t weigh in if he’s so inclined! However, here are some published fasting guidelines Dr. Fung has, and you’ll see, he allows cream in coffee even when fasting, up to a limit.

      Also, if you use the site search feature at the top right of this page and search for “beverages”, he has a post about beverages generally (although that doesn’t refer to beverages when fasting as such; the guidelines do).

      • Thank you Cristoph; this is helpful. My understanding is that fat intake has little to no effect on insulin secretion but I was wondering whether this intake of energy from fat could reduce the benefits of fasting. My interest in fasting is to lose some excess belly fat. Cheers!

        • My guess is sure, it probably does, a little bit. However, if it’s still mainly beneficial and the cream in your coffee makes it easier for you to fast, than that little bit of less effectiveness is probably worth it.

          Alternatively, if you can fast for 16 hours without coffee and cream, but 24 hours with, then I’d say the “with’ is also clearly more effective.

          Best of luck.

          • Christoph – thanks again and I agree with your thinking. A cup or two of coffee with cream does seem to help me maintain or extend a fast. Cheers

  11. I am T2 diabetic on a LCHF diet since 2012. I just started fasting, and my longest was 48 hours. To my disappointment my blood sugar started in the day with 9.7 and by the end of 2nd day was still as high as 6.4. Have to mention I did not take my medication during the 2 day fast.
    In a normal day ( I skip breakfast and lunch and have a feeding period from 5-8 and sometimes from 6-9), I wake up to a 7 – 7.2 , sugar continues to rise to 9 or 10 until noon, in the afternoon goes down to 6 by 5 o’clock. I take my pills, I eat meat and fat almost no carbs, I drink some red wine and by the time I go to bed the sugar is down in the 4’s. So I was wondering why fasting is not working for me. I am determined to try again.

    Now, not related to my question, in the picture of Martin Berkhan – one can see that his right arm is much bigger that the left arm and not in proportion with his body all together – just saying – Photoshopping comes in mind –

    from a T2 diabetic computer geek

    • 1. It’s a totally different angle, both in terms of orientation of the camera relative to his arm, and the angle of his arm itself, and I think your comment alleging Martin Berkhan photoshopped this image is BS. There are other images of his arm. They are more or less symmetrical. (But they’re rarely ever symmetrical: usually the non-dominant arm is larger because it has to compensate for less neuromuscular efficiency in the recruitment of muscle fibres. This becomes more noticeable the larger the arms. I hope no one ever accuses you of photoshop because your, er, body parts, aren’t exactly the same size. Or accuses you of plastic surgery. Or whatever.).

      2. You’re comparing fasting without medication to taking various undisclosed oral diabetic drugs on a low-carb diet and looking at blood glucose as the end all and be all marker? It’s not a fair comparison.*

      Protein raises insulin significantly, but not blood glucose. Fat raises neither insulin nor blood glucose very much. Oral diabetes drugs; including insulin mimetics, secretagogues, and any drug which raises insulin; will lower blood glucose significantly. It is not at all surprising that a low carb diet and diabetic drugs achieves lower blood glucose numbers than no carbs, but no drugs.

      3. You’re missing the point. It’s about insulin, not blood glucose. You’re trying, here, to get at the root of the disease by, over time, increasing your insulin sensitivity, not simulate a healthy person’s blood glucose readings artificially, and think this makes you healthy. It does not.


      4. Anyway, the short answer is lowing your blood glucose by fasting is not failure, and you can’t expect it to lower as much as a very low carb diet + pills. That isn’t scientifically—at least not right away. Long term it might. First, you have to improve the underlying insulin sensitivity which can come about because of reduced exposure to high-levels of insulin (which your oral drugs may exacerbate, and even protein in excess can), and possibly reduce the lipid in muscles and certain organs which may be part and parcel of reducing insulin sensitivity (although these are likely related since insulin’s job is to drive fat into cells) through interrupting intercellular signalling.

      You’re fine. It’s working well, considering how new you are to it. My tone may have been a little on the assertive side, but I feel you libeled Martin Berhan with nothing like proof or a reasonable, concerted, and conscientious effort to understand if what you were saying is true, so that’s what colored my reply. As for fasting, I think you’re doing great.
      *I’m noticing a pattern.

      • I am not against Martin Berkhan or his ideas. In fact I try to apply some of them – even though I think his audience is intended towards mostly men. The computer geek inside me found the picture funny, I still think it is ( look at the light and shadows cast too). Anyhow, that is not my point, was just a little funny diversion.

        For medication I have to take 2 metformin and 2 glicazide in the morning and repeat the same in the evening. I started lchf in 2012 when my doctor wanted to put me on insulin. Now I am on a plateau ( better said the a1c is creeping back up – last was 6.8 and i know the trigger for insulin is a 7) and in disperation I tried fasting. So desperate I would try for a few month if it was is required to get me in control. Because right now, no matter what I do I do not have a consistent and predictable response of my body.

        Getting back to you reply, I find point 4 very confusing – if you could explain in another words I would really appreciate. Should I continue with fasting or lchf and pills? Thank you in advance.

        Same T2 diabetic computer geek

        • I don’t even think LCHF is a good idea.

          However, my main point is of course you’re going to get lower blood glucose numbers on a very-low-carb diet plus two oral diabetes meds. When you fast, your body just draws fat from wherever and glucose, mainly from your liver, which is probably producing too much glucose already since your hbA1C is creeping up, as you’ve noted.

          Fasting isn’t designed to immediately get your blood glucose as low as a low-carb diet and two meds, one of which increases insulin. It’s designed to reduce insulin and, largely through creating a short-term calorie deficit, allow you to reduce some lypid in your muscles and organs as well. This is all with the goal of increasing insulin sensitivity, allowing your body to work more normally.

          Eventually, that should include better blood glucose control, but you can’t just compare a little fasting which your new at to VLC + 2 drugs. Doesn’t make sense.

          It’s like comparing a healthy lifestyles to amphetamines and coke and going, “Hey, why don’t I feel so energetic?”

    • *[reducing fat in muscles and organs being] part and parcel of reducing insulin resistance, I meant to say

    • Elena,

      I’ve been T2D for 15yrs and have been doing LCHF for the past year. Previously, i did Low Carb for 2 yrs. I now take 5mg glipizide in the morning. I used to take 10mg glipizide/1000 mg metformin in the morning & evening before LCHF and my BG was still poorly controlled.

      Now, my highest BG readings are in the morning, usually 90-120, but sometimes 130-150. The solution I found when BG is that high is a brisk 3+ mile walk in the morning. I’ve had BG readings go from 140-150 down to under 100 after the walk and stay low the rest of the day. For me, it seems that the distance or time spent walking is a big factor. If i only do 2 miles, BG comes down but not as much.

      I’m starting IF now.

  12. Hi Dr. Fung,

    Do you have a book available? If not, why? ,,,or maybe I should ask, when? 🙂


    • Hi Marie – The current release date is Jan 2016 by Greystone Books. I’ve finished my draft and its in the editors hands now.

      • Hi Dr. Fung,

        Great! I always find it more helpful having things clearly outlined in a book. I take it you will discuss fasting in your book. I was wondering will you also be discussing the appropriate diet that a person is to follow once he has completed the fast?

        Okay, January 2016 seems like a long time to wait. …I’ll be patient! 😉 LOL

        Thanks, again!

  13. Hi Jason,

    I am looking forward to your book.

    I am wondering on your thoughts on bulletproof coffee (butter + coconut oil + coffee) in the morning instead of breakfast. Specifically, i am wondering if this would have an impact on autophagy? i.e. would the small amount of protein in butter / high calories downregulate autophagy?

    Should i just fast with coffee and maybe some coconut oil (as per the perfect health diet).


  14. Hi Jason, I would want to join IDM program. Before doing so I want to now if you are for a vegan diet or LCHF (mostly meat and fats) diet after coming out of fast.

  15. Phuong Le

    Does anybody have problems with GERD , stomach pain like ulcer stomach pain when fasting? I tried fast 10- 12 hours but more than that my tummy will be painful … then the feeding time I feel a lot hungrier than normal, I have to make up eat the same amount of food that I skip…

    Maybe my body set the amount of food I eat daily and don’t want to reduce…but eat too more than my normal amount of food at each meal is very uncomfortable, heavy pressure on tummy… I have to take digestive enzymes for big meal, normal meal I don’t need it….I don’t like to use any additional supplements unless I absolutely have to…

    I am in just right weight, I don’t want to lose weight, mostly have a hard time to gain weight due to my body refuse to let me eat more ( uncomfortable, can’t sleep)… I just want to use fasting to control my diabetes.

    I am type II diabetes however My Dr. still want me to control with diet because my A1C fluctuates every 6 months test from 6-6.5 and fasting BS fluctuates from 105-120… Dr. feels I can control with just diet alone, eventually probably need Meformin.

    That why I want to try fasting to see how if it helps me… My normal diet is 3 big meals a day with veggies ( 1/2 raw salad, 1/2 cooked variety of colorful low carb veggies, protein and fat is main portion , for carb I have 1/2 cup of bean or sweet potato, 1/2 cup of yogurt full fat with a bit of fruits like berries. I try to keep my carb 20-30 gram for Breakfast, 40 gr for lunch and 50 gram for dinner…Protein eats about 3 0z each main meal , fat is in protein ( mod fat meat type ) and 2 table spoon olive oil for veggies. Additional a 1 hour before bed snack with 1 0z of nuts ( mixed of almond, walnut, pecan and one Brazil nut) and 1 Tablespoon of GreatLake gelatine mix with a cup of Chamomile tea. I did not count carb for this snack…
    If I don’t have this snack I will wake up at 2am and am very hungry with stomach rumbles , with the snack I sleep peacefully through the night.

    I can fasting 10-12 hours a day but if I fast more than that, my tummy hurts…. right now I fast 1 a week 16 hours, weekdays 10 hours.

    I appreciate any help/ suggestions….Thank you very much!

    • Hi Phuong Le,

      I have never experienced tummy troubles previously, until last night.

      I just started the LCHF diet one week ago. I have been ravenous (mainly from 3:00 p.m. till I go to bed). They say if you are hungry you are not getting enough fat in your diet. …well, I have never eaten this much fat at each meal in all my life. …I can’t really say I’m following LCHF, because I find after 3:00 p.m. I am continually snacking and I have to take a bowl of fruit salad (with cottage cheese and walnuts) before I go to bed just to keep from going hypoglycemic.

      Last night I decided to try to make some chicken broth. (I thought that because it will be six months before Dr. Fung’s book comes out, I should try to get started on things I know, so I don’t have such a learning curve when I actually do the fast.) After several hours the broth was smelling so good that I thought I would take a sample. …it was so delish that I decided to have a whole cup of soup broth! Usually I always cool the broth down and skim the fat off before I drink my broth. But I reasoned it would be okay to have it without the fat being removed since the LCHF doctors said that you should eat the skin on your chicken. The cup of soup broth was so tasty, that I had another one!

      Well, about five hours later I wound up with incredible pains in my stomach. I’ve never experienced anything like that before. I knew what it was, since I haven’t made homemade broth in decades.

      So, this morning I was thinking about this. This past week, I’ve been having incredible problems with all this fat (although the problems maybe merely psychological). I’ve always been on low fat diets in the past. Last night I started to eat my salad without dressing, as I couldn’t stomach having my normal oil and vinegar dressing (that I am allowed with LCHF).

      But this morning when I stepped on the scale for my first weekly weigh-in I dropped 5 pounds. This is amazing. So, now what do I do? The LCHF diet seems to be working. Interestingly, the first day I did LCHF my blood sugar readings all went level–no spiking and dropping. However, I had been experiencing lows a few days after that. I am going to continue to monitor this situation, as I may need to start going off some of my diabetic medicine.

      I think in my case, regarding my stomach pains, the problem is fat. Have you examined your diet closely to see if you have any food triggers that might be causing your stomach pains?

  16. Elena

    May 26, 2015 | Reply

    Hi Jason, I would want to join IDM program. Before doing so I want to Know if you are for a vegan diet or LCHF (mostly meat and fats) diet after coming out of fast. I am T2 diabetic since 2004, and on LCHF diet since 2012. A1c maintained between 6.1 to 6.8. Canadian Diabetes Association standard diet was/is a disaster for me.

  17. Thanks

  18. Dr. Fung – I can’t wait for your book to come out! I’ve only been following your protocol since May 15th, but am already reaping benefits from it. I’m down over 13 pounds, and have been taken off of one (of two) high blood pressure medication. I’ve been fasting for 36-38 hours every other day and feel fantastic! Thank you so much!

  19. Hello Dr Fung,

    Do you have any opinion on magnesium supplementation to improve blood sugars/insulin resistance? I have been following LCHF for a long time and recently began gaining weight. I have been suffering with stress, lack of sleep, increased craving for carbs etc. After researching what might be causing this I stumbled on magnesium deficiency and have been supplementing for the last few days.
    The main thing I notice is a lowering of hunger.
    Maybe a future blog post? I would love to know your thoughts on the mechanism of magnesium in the body.

    • Magnesium is the one supplement that we use the most. We often test serum magnesium levels and they are often low in diabetic patients. Also, many people complain of constipation and cramping which can often be helped by magnesium supplements. Whether it lowers blood sugar is debatable.

      • Dr Fung do you also find the same issue with magnesium with obese but non diabetic patients?

  20. You haven’t shared any thoughts on the subject of women and if we benefit or not from IF.
    I’d be most greatful if you would!

  21. I apologize if you have answered this elsewhere, but I’m wondering what your thoughts are on fasting and adrenal fatigue? I’m a LCHF marathon runner and have had issues with adrenal fatigue in the past, but am intrigued with the idea of daily fasting. Thanks!

  22. Hi Dr. Fung,

    Okay, a different “Marie” here. (But so thankful the other Marie brought this subject up.)

    Is it safe for a person who does have adrenal insuffiency and is taking corticosteroids to fast?

    Are there any medical conditions where it is not safe for a person to fast?

    • If you don’t feel well for any reason during fasting, you should stop immediately. Certain medications may cause problems during fasting. Adrenal insufficiency and steroid use is not a contraindication.

  23. Does missing meals/fasting cause stomach ulcers? That is one argument people have told me whenever I tried to skip my meals.

    • Danielle

      Not at all (just make sure you’re not chewing gum to ‘fill the gap’ because your stomach will begin digesting food that isn’t there, which could cause ulcers for sure). And if you’re drinking the proper amount of water (which is an alkaline solution), you shouldn’t suffer any ulcers, stomach acid or anything like that 🙂

  24. Hi Sarah,

    I have never heard that fasting or missing meals could cause ulcers. In fact, if missing meals caused stomach ulcers I should have had ulcers a long time ago. While I do have a lot of health issues, to the best of my knowledge, I do not have ulcers.

    There was a lot of media attention given to a certain doctor, quite awhile ago, that ulcers were caused by bacteria and could be treated with antibiotics.

    I did a very quick search and found some information on ulcers at webmd. I think they are a fairly reliable source of information.

    And, just to let you know that Dr. Whittaker actually has his diabetic patients do what he calls intermittent fasting. This is where people skip breakfast. (I don’t think he would recommend skipping a meal or fasting if it was to cause ulcers.)

    So, I sure question what these other people are telling you.

    With that being said, maybe someone else has better information on this matter.

  25. George Munoz

    Hello Dr. Fung,

    I am interested in following the Leangains protocol in which i fast for 16 hours and workout 3 times a week. I was wondering if eating a high carb diet such as 40p/40c/20f would still be ok since i am fasting for the majority of my day to keep my insulin sensitivity high?

    • Danielle

      Hi George

      I wouldn’t recommend a high carb diet at all, fasting or otherwise. Without going into a huge essay about it, a high carb diet is what causes insulin resistance/T2 diabetes, regardless of how “healthy” it is. You’re no less likely to develop insulin resistance or related diseases just because you fast in-between high carb meals.

      HFLC can eradicate this risk almost entirely (the lower carb you go, the less risk of heart disease, stroke and diabetes you’re at), because again it’s not about how rarely you eat the carbs, it’s about eating them in the first place. The very reason so many 30 year old athletes in the prime of their careers suddenly drop dead is because of high carb diets (since they are inflammatory, which is what causes heart disease, not fat as the mainstream media tries to say is to blame).

  26. Thanks Marie.. Those links are helpful. I’m also a big lover of missing breakfast in spite of what people around me advice… Though recently I happened to try the 24 hours fast that Dr Fung recommends… I like it a lot as I feel much more alert and am able to concentrate more on work. In fact, I prefer the 24 hrs fasting days than the normal eating days.

    • Hi Sarah,

      Thank you for sharing your experience with the 24 hour fast. This is very encouraging.

      I haven’t tried doing this fast yet. I have a chronic complex medical condition and my own health is fragile. I want to make sure I read Dr. Fung’s book and get all of the information before I jump into the deep end.

      Previously, I had tried Joe Cross’ juicing fast, but I only lasted three days. I became very weak and sick. So I had to give it up. I cannot tell you how disappointed I was, as I really wanted to continue.

      I still haven’t given up on the idea of fasting, because I have seen spectacular results with my own mom. My mom went into the hospital a few years ago with a gallbladder necrotizing pancreatitis attack. One of the main lines of treatment was fasting. She was NPO (no food and no water). We were told that this was to let her gallbladder/pancreas rest. This went on for months. She was only allowed portions of ice chips. I thought it was so cruel that the doctors and nurses wouldn’t give her water (since she was always telling us how thirsty she was) that I went to the Internet just to make sure that we were being given the correct medical information. Sure enough, that was the standard treatment. So, I settled down and just gave my mom these small ice chips.

      Then on another occasion they found a fistula. Once again, we were told the treatment was NPO (no food and no water). This time my mom was madder than a hat and went out and screamed at the doctor that no one would give her food or water. But after one month of being NPO my mom did not have a fistula any more (thus avoiding another operation).

      While my own mom did lose a lot of weight (in fact, by the end of it all, the doctors were wanting her to gain some weight!), she was still diabetic. I don’t know why fasting didn’t “cure” her diabetes, but it didn’t. Perhaps it was because of all her other complications.

      But my mom did come home from the hospital. I am thrilled that she is so happy and is enjoying the sunset years of her life.

      So my point is that the medical profession does know about the benefits of fasting. I’m sure there are a lot more situations where they use fasting in their medical treatment protocols.

      That is why I think that Dr. Fung is really on to something big with fasting for diabetics. I suspect this treatment could really help a lot of diabetics.

      Until Dr. Fung’s book comes out, I will continue with my baby steps. I’m doing the Low Carbohydrate High Fat (LCHF) diet and have just started making homemade soup broth. If you haven’t done this, be sure you try it. This broth is so good–and from my research it is good for you! I must tell you that it is really helping reduce these incredible hunger pangs that I experience with the LCHF diet.

      • It’s encouraging to hear about your mom, Marie. But do be careful if you have health complications. I’m also on LCHF though I tend to fall off the LCHF on weekends while eating with family. Yes Bone broths are delicious. Indian cuisine has many such soups eg the mutton paya soup, chicken bone soup, beef soup. Since most of these are not available in shops, we make them at home anyway. Haleem (without the broken wheat) is also delicious and nourishing though not much bones there. We also make stir frys with organ meats such as liver, heart etc. Though here in India the general tendency is towards vegetariansim or low fat high carb diets and most things non-veg is considered unhealthy. So we need to go against the tide to follow LCHF which I’ve been doing for myself 🙂

        • Hi Sarah,

          Thank you so much for sharing this with me! Just yesterday, my husband came home with an Indian cookbook. He said that he thought that I could eat this and be faithful to my diet. I made him read all the ingredients to me. I was surprised that everything was on the LCHF diet.

          My husband loves to cook and is frustrated that I just want to eat simple food. The Indian dish that he made for dinner was delish! I will look closer at his cookbook to find new recipes.

  27. Jennifer

    Hi Dr Fung,

    Why do you consider it ok to include coconut oil or cream in coffee during the fasting window? I thought any calories would break the fast (and hence reduce the benefits), is it to do with coconut oil and cream not affecting the insuline? (although one of your previous posts have touched on milk protein raising insuline…). I would really appreciate a respone on this, as if no benefits are lost I will definitely prefer to drink my coffee with cream or coconut oil, or take a spoon of coconut oil when hungry during the fast period. Thank you for a great blog, I have read all your posts this week and everything makes so much sense!

  28. […] classification purposes. There is no magic dividing line. We covered fasting regimens using periods less than 24 hours in our last post. This post will cover those schedules that use fasts longer than 24 […]

  29. Hi, Dr. Fung,
    my last blood test is 8.6(no fasting), HA1Cis8.9, I am taking insulin. I am not sure if fasting is work for me.

    • Well, Liane, you haven’t given any details of what you’re doing in terms of fasting, diet, etc; how long you’ve been doing it; what else you’re doing; when these tests were done; when and what your previous tests were; etc.

      I’m not saying it is working for you. I’m asking, what informed comment can be made just based on what you’ve written?

      • When I did the blood test in April, I am taking three meals like normal people but I try my best to eat healthy. I also start taking meffumin two tablets twice a day. The medicine make me uncomfortable. Now I have to start using insulin at bedtime everyday. I check by my meter. Fasting around 6.6, after meals 2 hours around 10. I only eat vegetable, fruits and proteins.

        • Hi Liane,
          I am diabetic too, and my family doctor wanted to put me on insulin. I thought I was eating healthy, however the blood test showed very high sugar numbers. I started eating one food at a time, and measure my blood sugar, before, after, after, one hour after and 2 hours after. I started eliminating the foods that gave my high sugars after 2 hours. After a while, when I was able to content without these foods, I started eliminating the foods that gave me high sugars after one hour and so on. I think it is worth trying, as every food (vegetable and fruits too) react differently with us, and identifying the ones that are bad for you is important. Otherwise, jumping from one diet to another, listening to whoever is out there on internet, won’t take you very far.

  30. My sugar around 9 if i don’t eat bread, potato, rice, pastas. So I only take carbohydrates from fruits. And I want to reach the target for diabetics, fasting under 7, after meals 2 hours under 10. But it is hard to keep under 10, sometime around 10.5

  31. Hi Dr. Fung,

    Great work here!! Have you noticed any link between any of the fasting regimes and issues with gallstones? I understand that long bouts of not eating contribute to bile build-up in the gallbladder and the potential creation of gallstones. I’d be interested in hearing about your observations and what studies may say to reduce the chance of this happening.

    Please keep up your great work!

    • Jennifer

      Hi SVM,

      I know Dr Andreas Eenfeldt has written about gallstones and LCHF diet on his webiste and I think maybe there is a link between the gallstone discussion for LCHF and fasting. I’m no doctor but my understanding is that fasting or LCHF does not cause gallstones, however consuming more fat (or possibly by fasting and hence entering ketosis) will flush/clean your gallbladder so if you have any stones in there (most likely casued by carbohydrates clogging effect in all veins/arteries and organs) that has not yet been noticed, it can happen that these now get flushed out with the help or fat consumption (or maybe ketosis).

  32. Hi Dr. Fung

    For someone with kidney disease from diabetes, do one have to also avoid fats which are high in potassium and phosphorous? will kidney disease be an ongoing issue even when sugars are under control from the change diet and intermittent fasting?

    Dr. Jason Fung: The kidney disease is not easily reversed, even though the diabetes itself can often be reversed. The damage is usually already done.

  33. Thank you Dr. Fung

  34. Hi there, just finished reading this series…what an abundance of good information! I’ve been doing IF for about 3 weeks now, mostly the 16-8. I’m an endurance athlete and am currently around 6% body fat. I feel great on this schedule of eating but was wondering what is the longest fast you might recommend. My main goals have to become better fat adapted in order to reduce my caloric needs in races/be able to maintain a high intensity while burning a high percentage of fat. Any advice would be great, thanks!

  35. Hi Dr. Fung
    I love your website.I am vegan for a year now and have gained 10pounds, I am trying 16:8 intermittent fasting for 3 weeks and haven’t lost any weight.
    what is a good fasting insulin level? i want to check it with my next blood work.
    I am not diabetic just want to avoid it and lose 30 pounds

    • Danielle

      You’ve gained weight because veganism is an all-sugar diet. Try eating more meat.

  36. Have you read “Fasting and Eating for Health” by Joel Fuhrman? It’s a pretty scientific read on the subject and came out in 1998, long before any of these books mentioned.

  37. My dear Dears, I ‘m screeming for your help!
    I won’t bother with to much details : 66yo, obese, diabetic, no medication, hypertention…. And damaged liver by hard drinking .
    I know the esentials, I already began alternate day fasting which I love ( in fact i did several one month fastings in my 30-40s) , but I need advice on diet coreleted to my liver problems.
    (Sure no more booze!
    I like avocados, organic coconut oil eaten by itself , eggs, extra virgin olive oil, salads ,organic vinegar, Irish butter , not to much meet. I love carbs , starchy vegetables , legumes , sure I have to give them up .)
    Help me please, in structuring the base of my diet, nutritive requirements, and portion size.
    Thank you so much, Steven

    • Because we are all individuals and react differently to foods and especially carbs, my advice is to use a glucometer. Eat one food at a time and change the size until the BG is in normal levels. Of course you have to be ready to eliminate some foods through this method. For example for me 6 cherries bring my BG to 200 for the next 3 hours and I need a fist of pills to bring it down – so I considered it is not worthy.

  38. can I have high insulin levels without insulin resistance ?

    since a little kid i was a little fat but my sugar levels is very low and I’m 35years with 30% bodyfat, sugar levels with 12 hours fasting is 80, I feel like I have hipoglicemic levels sometimes, when i eat carbs without fat ..

  39. during the 16 hour fasting period would it be ok to drink kefir (water grains, with fruit juice used for secondary fermentation)?

    • Danielle

      Nope. Fruit juice = sugar (no such thing as healthy sugar). Just drink water.

  40. I’m struggling with WHY in the intervals the body becomes fat burning; i.e. burning unwanted fat already stored. Won’t it attempt to use the stored glycogen and isn’t there sufficient for the 16 hours right there?

  41. I’ve been fasting 16+ hours daily and eating moderate carbs for the last 2.5 years, lost 40kg and now normal BMI and waist:height ratio <0.5. After reading the research on individual blood glucose responses to foods depending on gut microbiota variations (Zeevi et al, Cell 2015; 163: 1079) I invested in a blood glucose meter. Although fasting BGs are good (around 4.2 mmol/l) I was shocked to find my post meal BG is higher than it should be with the peak delayed. After a pork and veg meal containing carbwise a half cup of cooked brown rice and chickpeas, taken with a glass of wine, and followed by around 3 tbsp stewed apple (ie with a little added sugar) with full fat greek yoghurt, my BG went up to 8.4 mmol/l at 2 hours after eating, and at 3 hours was 5.5. Next morning BG was 4.2 and remained low until lunch. After lunch BGs reach around 7 at 2 hours. My question is: should I be worried about 2 glucose spikes a day or should I be cutting carbs further?

  42. I’ve been doing the “Warrior Diet” for the past 3 weeks and have already lost 13% of my body mass. I drink 32oz of fresh vegetable/fruit juice with some psyllium husk fiber and some vegetable protein supplement in it every day at 3pm. I have about 10 more pounds to go, though my target weight is somewhat arbitrary (just going to lose weight until I can see my abs again, more than likely). I usually eat a hearty meal on Sundays to kind of “reset”, as by day 6 the persistent elevated fasting adrenaline levels get to be a bit overwhelming and I’m bouncing off the walls!

    P.S. The ugly pea-sized lipoma I’ve had on my left shin for over 20 years has all but disappeared do to this fasting regimen. Bonus!

  43. Hi,
    I’m wondering if some inulin powder intake during fasting days is useful/advisable or it can somehow “break” the fasting.

    Thanks for info.

    Max from Italy

  44. I have watched your videos on youtube. Thank you for your free information. I am Type 2 diabetic. I have been obese all my life and was diagnosed with diabetes 3yrs ago. My NHS doctor is not onboard with fasting and I can’t afford a private doctor but I want to fix myself by fasting, after watching your videos. I have been HFLC for a couple of years but I have not lost weight and I still weigh 290lbs. My GP recommended 20 units insulin a day and my blood glucose has never been higher than 150 in the morning and is usually 120 dropping throughout the day and into the evening… so I have reduced this to 6 units on my own decision because I thought it was just the morning effect. I have usually only eaten once a day since going HFLC and following the advice of Dr Bernstein (despite my doctor saying I need to eat carbs) and have always started the morning with a creamy coffee and eaten once in the day only at early evening. So I figured it would be easy to start fasting 24hrs as your website says. So I tried fasting 24hrs yesterday and 16hrs later (now) I feel kind of high in my head, very odd and I just tested my blood glucose to see it is on 248 even though this morning it was only 89. What is going on? I have not eaten anything since then and drank only water. What is happening? Is it true I can’t fast? I guess you see this a lot? What do you suggest to your patients at that point? Thank you

  45. Thank you for this wonderful website.
    I’m very much interested in fasting to bring down insuline.
    Could eating only fat all day, in coffee and tea, have similar effect on insulin levels?

  46. T-squared

    Dr Fung
    I am very much interested in trying this but i am having a hard time figuring out how to get started. You have a lot of information backgound and history on the subject that has interested me. However, where do i begin. I am pre diabetic and need to lose weight. I dont want to go on medication. I have tried many diets only to gain the weight back plus more. Please let me know where i can find the steps to get started with this….really need your help

    • Danielle (Dr. Fung has made many videos on this website about LCHF)

      Simple way: using intermittent fasting, cut all sugar, pasta and bread out of your diet as a first step, and increase fat content from there using fish, butter and meat (don’t cook with oil it’s poison)

  47. John Headon

    re kidney disease, my blood sugars are stratospheric for last few years, guess what no protein in urine, plenty of sugar. Successfully losing fat by intermittent fasting and fat gobbling after medics in hospital doubled my insulin but sugars did not respond except to go up! Yep I’m angry at conventional medics.
    Protect your kidneys with Benfotiamine and B1 through the day every few hours. Blood pressure meds do NOT protect kidneys only damage you. Diet change and hawthorn fruit/leaves tea, more effective for BP fix. Eat plenty of sea salt, forget the docs as this contains trace minerals essential for your kidneys and adrenals and during fasting and will reduce your blood pressure if that caused physical damage to the kidneys tubules. You might get some repair like mine so your GFR will rise.
    I am now on Pigs insulin, a natural insulin Hypurine Porcine Isophane/neutral and changed to this after liver ALT enzyme evidenced substantial damage. ALT enzyme now really low showing liver recovery. GFR went low at same time evidencing kidney damage too. Took a few years after insulin change to fix. If you missed the point See the previous synthetic and also GM so called human insulin (certainly not human) caused my organ damage! Switch to Pigs insulin above dose 1 for 1 available from Wockhardt on prescription in UK and neutral is actually best for automatic dosing machinery as is common in the USA. Special presciption may get it to there but drug companies are trying to block it worldwide. Overdose of this like any other insulin, ups blood pressure, lipids, heart /circulation problems and type 3 diabetes which is brain fog/memory. Eat at least 2 dessertspoons daily of plain cheap coconut oil( KTC brand about £2 per 500ml thanks to UK 20% tax to sell unhealthy rapeseed/canola oil) as part of your healthy oil ration with meals to defog you.
    OK hope you can benefit from my own experience here. Dr Fung already evidenced modern GM insulin causes secondary effects of diabetes but the truth is a little worse than that and profitable so they want to shut out superior competitors from their market. Pigs insulin made from pigs pancreas has been around about 50 years.

  48. Hey

    I have been fasting for 10 says now and aiming for 14. Maybe more. I use water mainly.
    I have read that it could be quite a stress for the heart muscle doing longer fasts. Any comments regarding that?

    And I wonder if it’s safe doing some slow tempo bicycling during longer fast?

  49. Hi Jason,

    I really like your articles, thanks heaps for posting them on a public forum where we can all read them and benefit from them.

    I tried a regime for a few months where I stopped eating at 8pm, and did a 16 hour fast broken by lunch at 12pm, but I found that I got REALLY sleepy after lunch. I liked the regime and I didn’t find it difficult to skip breakfast, but I had to go out and nap in my car after lunch which mucked up my work day a bit! I was wondering why this sleepiness occurs, and if it is a common experience.

    Emma from Australia

  50. […] Longer fasting periods such as that eighteen hour fast are considered to be intermittent fasting protocol. Intermittent fasting (IF) is a term for an eating pattern that cycles between periods of fasting and eating. It does not say anything about which foods you should eat, but rather when you should eat them. Some people will choose to use intermittent fasting daily, while others might fast for just a couple of days each week or every other day. You can read a great post on intermittent fasting here . […]

  51. How low should fasting insulin be?

  52. What about the Fast 5 diet, which was published around 2005? Bert Herring’s contribution to the field and not a rip off, as far as I can see.

  53. Dr. Fung – would intermittent fasting be beneficial for glomerular disease? I’m very disciplined and would love to try this to find out if it would improve my kidney autoimmune. Many thanks!!

  54. […] Longer fasting periods such as that 18-hour fast are considered to be intermittent fasting protocol. Intermittent fasting (IF) is a term for an eating pattern that cycles between periods of fasting and eating. It does not say anything about which foods you should eat, but rather when you should eat them. Some people will choose to use intermittent fasting daily, while others might fast for just a couple of days each week or every other day. You can read a great post on intermittent fasting here . […]

  55. As much as i love fasting (doing 24 hours fast) i need to say that diagrams are wrong and some information isnt really precise either.Insulin status isnt really so important for fat burning,you will not burn fat in calories surplus wven when insulin is low because insulin is just one of many players in human body.If you eat a lot of fats which areny really insulinogenic you still block AMPK switch,high level of circulated fatty acids blunts GH release and adiponectin is low.Your body will produce only as much insulin as is needed to remove excess glucose (if you are healthy) thats why you can eat 1000kcal of sugar divided by 24hours and you still will lose weight.
    Imo focusing on insulin is misleading and incorect because insulin status isnt corelated with weight loss.

  56. Terri Sartoris

    Dr Fung, There is a great debate on this: Is it ok to do a 24 hour fast every day? In essence just eating one meal a day every day for long periods of time? People say you will burn muscle this way. People say it will throw you into a stall and you don’t recommend it. Please clear this up for us! 🙂

    • Danielle

      Fasting will only burn muscle if you have no more fat left to burn, and when you DO eat, make sure you eat a low carb diet.

      If you’re already very slim, make sure you add an appropriate amount of healthy, natural fat (no oil) to your meal (this way your body uses the food as energy, and not your muscles). So cook in butter, or eat salmon, etc. If you’re very overweight, just cook the meat normally without excess fat so that your body ‘eats itself’ instead of your food.

      This will prevent that gross muscle wastage that you see on a lot of fat-free or vegan dieters.

  57. hi Dr. Fung, thank you very much for your very helpful blog posts and book (I just received it from Amazon this afternoon and devoured it in one sitting, lol!).

    So is the main difference between daily intermittent fasts versus longer fasts simply the dose of lowered insulin levels required to prevent/reverse insulin resistance? If someone is not overweight and fairly active but has a little bit of belly pudge, would you still recommend getting an OGTT and/or HOMA-IR to test for insulin sensitivity?

    Also, if part of why intermittent fasting works is that it is intermittent (as opposed to, say, constant caloric restriction), wouldn’t the body simply get “used” to a regular 16:8, 20:4 or whatever eating cycle?


  58. I don’t drink coffee and tea gives me heartburn/reflux, so I wanted to find out if replacing coffee/tea with Kaffree Roma Roasted Grain Beverage is ok? (it’s roasted barley, roasted malt, roasted chicory, roasted rye)

    A scan of the label is on the product listing on Amazon here –

    It does have some calories (I think coffee has 2 calories per teaspoon, and this has 10), and I’d take it with a tablespoon of heavy cream.


  59. Great articles.
    You mention that the 12 hour fast will not repair insulin resistance.
    You don’t mention which fast does.
    It would be great to know the minimum fast regimen that would repair insulin resistance.


    • I should have read the post more carefully. The answer is here:-
      ” by incorporating daily, or almost daily periods of low insulin, we are able to prevent the development of insulin resistance and even reverse relatively minor levels of resistance. For more established resistance, we would need longer fasting periods – 24 hours or greater.”

  60. Karen Fisher

    Kids. What will you teach yours? Will or do you give them an eating window? My 11 year old is overweight. I have been doing IF with success. What shall I tell him?

  61. I have adrenal fatigue and PCOS. I know that IF is not recommended with adrenal issues but would doing shorter fasts such as 16:8 be ok? I want to try to deal with some of the PCOS issues and insulin resistance. Any advice would be appreciated.

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