Longer Fasting Regimens – Part 7

posted in: Fasting, Health and Nutrition | 105

There are several longer duration fasting regimens that are available. I arbitrarily divide it at 24 hours but there is no physiologic reason to do so, other than for 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 hours.

24 hour fasts

This period of fasting is essentially going from dinner to dinner, or breakfast to breakfast, whatever you like. For example, you would eat dinner at 7 pm and then fast until the next day’s dinner at 7 pm. In this regimen, you do not actually go a full day without eating since you are still taking one meal on that ‘fasting’ day.

This is very similar to the ‘Warrior’ style of fasting although that allows a 4 hour eating window so is technically a 20 hour fasting period.

This period of fasting has several important advantages. First, as a longer duration fast, it tends to be a little more effective. Because you still eat every day, medications that need to be taken with food can still be taken. For example, metformin, or iron supplements of aspirin should all be taken with food and can be taken with the one meal on the fasting day.

The other major advantage is that this style is the most easily incorporated into everyday life. Most people, for example will eat dinner with family every single day. As you still eat dinner every day, it is possible to routinely fast for 24 hours without anybody knowing any different, since it really only means skipping breakfast and lunch on that day.eatstopeat2012

This is particularly easy during a workday. You simply drink your morning cup of joe, but skip breakfast. You work through lunch and get home in time for dinner, again. This saves both time and money. There is no cleanup or cooking for breakfast. You save an hour at lunchtime where you can work, and be home for dinner without anybody even realizing you had fasted for 24 hrs.

Eat Stop Eat

This schedule of 24 hour fasting done once or twice per week is recommended by Brad Pilon in his book Eat, Stop, Eat. Brad was a bodybuilder who was a pioneer in popularizing intermittent fasting and really undertook a thorough review of the science behind fasting. This book is often considered a ‘bible’ of intermittent fasting, and I would highly recommend it.

Dr. Michael Mosley
Dr. Michael Mosley

The 5:2 Diet

A related approach is the 5:2 approach championed by Dr. Michael Mosley, a TV producer and physician best known for popularizing this approach. He appeared on a BBC program called Horizon entitled “Eat, Fast, and Live Longer”.

While there had been some fringe interest being generated by pioneers such as Martin Berkhan and Brad Pilon, they had not really hit the mainstream yet. With the BBC documentary and the book that soon followed, intense interest, especially in the UK followed.

The book, entitled “The Fast Diet” became a best seller in the UK and soon other follow up books were released. The basic diet was not quite a 24 hour fasting period, as Brad Pilon described.

Instead, the 5:2 diet consisted of 5 days of normal diet. On the other two days, you could eat a total of 500 calories. Those 500 calories could be taken all in a single meal. If, for example, this is taken as dinner, it would be identical to the Eat, Stop, Eat diet. However, you could spread those 500 calories out into multiple meals instead. These two approaches are quite similar and the difference physiologically, is likely quite minimal.

Alternate Daily Fasting (ADF)

This is the dietary strategy that has the most research behind it. Much of it was done by Dr. Krista Varady, an assistant professor of nutrition with the University of Illinois – Chicago. She wrote a book about her strategy in The Every Other Day Diet, although this was not the blockbuster success of the 5:2 diet.

Krista Varady
Krista Varady

Even though it sounds like you only eat every other day, it is not quite. You can eat up to 500 calories on fasting days, just like in the 5:2 diet. However, fasting days are done on alternate days rather than 2x per week so it is a more intensive regimen. The major advantage of this regimen is that more research is available on this regimen than any other. We will consider these studies in more detail in later posts.

36 hour fasts

As you progressively go longer in fasting, there benefits accrue faster, but there is also more risk of complications. Since I often deal with type 2 diabetics and hard to treat obesity cases, I tend to gravitate towards longer fasting periods, but you must understand that I always monitor very closely their blood pressures, and blood work and progress. I cannot stress enough, that if you do not feel well at any point, you must stop. You can be hungry, but you should not feel sick.

Another major consideration is that medication must be carefully monitored by a physician. The major problem are diabetic medications because if you take the same dose of medication and do not eat, you will become hypoglycaemic and that is very dangerous.

Blood sugars going low is not a complication per se, because that is generally the point of fasting. We want the sugars to go low. However, it does mean that you are overmedicated for that day. You must work very carefully with a physician to adjust medications and monitor sugars. Also, there are certain medications that may cause stomach upset on an empty stomach. NSAIDS, ASA, Iron supplements and metformin are the major drugs here.

In general, diabetic medicates and insulin MUST be reduced on the fasting day to avoid hypoglycaemia. Exactly how much to reduce it should be overseen by your physician.


A 36 hour fast means that you fast one entire day. You finish dinner on day 1 at 7pm for instance, and you would skip all meals on day 2, and not eat again until breakfast at 7 am on day 3. So that is a total of 36 hours of fasting.

42 hour fasts

We often advise our clients to make a routine out of skipping the morning meal and break their fast around noon hour. This makes it easy to follow a 16:8 fasting period on regular days. After a few days, most people start to feel quite normal just starting their day with a glass of water and their usual cup of coffee.

When you combine that with a 36 hour fast, you get a 42 hour fasting period. For example, you would eat dinner at 6 pm on day 1. You skip all meals on day 2 and eat your regular ‘break fast’ meal at 12:00. This is a total of 42 hours.

For longer duration fasts, we often try NOT to calorie restrict during that eating period. Often, as people get used to fasting, we hear very often that their appetite starts to seriously go down. Not up. Down. They should eat to satiation on their eating day.

There’s a very good reason for this decrease in appetite. As you start to break the insulin resistance cycle, insulin levels start to decrease. Since insulin is the major regulator of the body set weight (BSW) your body now ‘wants’ to go lower. In response, hunger is suppressed and total energy expenditure is maintained. So – appetite goes down and TEE stays same or goes up. Remember that standard Caloric Reduction as Primary (CRaP) strategies produce the opposite. Appetite goes up and TEE goes down. Which do you think will work in the long run?

Start with Fasting part 1

Continue to Fasting part 8

105 Responses

  1. Heather

    Dr Fung, can I ask what your stance is on taking vitamins and other supplements while fasting? For instance, I take sublingual B12 (which contains xylitol) several times throughout day and don’t want to miss it on fast days. I also take a herbal supplement which lists rice as an ingredient. Will taking these with water disrupt the benefits of fasting in any meaningful way?


  2. Deb Griffith

    Thank you once again for posting your latest blog! Since I have already read everything else you have written, I was looking forward to more!
    IF saved my life and my sanity! I combine 4:3 and sometimes ADF with 16:8 and use guidelines learned here and from the Leptin diet. Stopped the long, gruelling cardio workouts and now just do 15 minutes of HIIT 3 times a week, and weights twice. 7 weeks in, 14 lbs down! I always KNEW there was an answer to this weight problem in the world. I had hoped to find it before I was dead, and I did!

    • What is 4:3? What do you do for 15 min HIIT? Do you use an app? Thank you and Congrats!!

  3. Judy Olson

    I have recently started doing two 24-hour fasts per week. Each time I have had forceful watery diarrhea about 30 minutes after my break-fast meal. Suggestions please!!

    • Same happens to me, can’t reason why!

    • I experienced the same for the first two weeks. Not nice…but 4 weeks in now and my digestive system seems fine now when breaking fast. My advice would be give it time.

      • I found the same thing, but it was more like 5 weeks for me. Your body just needs time to adjust to a new pattern.

    • nathanb

      I’ve experienced this unfortunate effect but I was able to alleviate the problem by eating an avocado with my break fast meal. I was thinking that my meat was too lean for digestion, especially on a really empty stomach! I think it helps to keep the reintroduction meal small as well.

      Don’t make yourself sick! Losing weight is not worth damage to your health.

    • One theory I have read is as follows:
      You eat supper and then stop eating. Since your body is not getting food, the digestive system slows right now.
      This means that the supper you had the night before sits in your digestive system.
      Once you eat again, the digestive system starts up and it needs to make room to eventually eliminate what you just ate.
      This will push the food out of your bowels from your evening meal.
      Also, fasting is detoxifying so your stool will tend to me have more fluid, hence it will be loose.
      Breaking your fast with a smaller meal may help.
      Also, if your first stool after a fast is hard, brace yourself because 30 minutes later the diarrhea may kick in.

      Not sure if this theory is correct but it does align with my personal experience.

    • I have had exactly the same problem. They took my gallbladder out about six years ago and I kind thought it might be due to the irritation from the bile salts in a basically empty gut. On long fasts ( I do warrior diet five times a week and two days where I don’t eat at all to resume eating the next day after five pm) I supplement with a tablespoon of psyllium husk powder in water every six waking hours or so. So far, knock on wood, it has taken care of the problem. Best of lucks!

    • When you eat, you trigger Peristalsis, which is the movement of food along the digestive tract.
      Since you are eating very low-carb with no fiber, water is being released.
      This will result in your situation.
      Your body is simply purging excess water with the bowel movement.
      As long as your electrolytes are maintained, there shouldn’t be any concern.

  4. Hi, You spoke of a successful year long fast. Is there a cut off time that you recommend?

  5. Deb Griffith

    I started reading Kristin Farady’ s book (The Every Other Day Diet). I was disappointed that she (so far anyways) seems to ignore the basic science behind food, and believes the calorie in, calorie out theory. She even recommends frozen dinners, tells readers that it doesn’t matter what you eat (carbs, low fat processed food..), or when you eat (even suggests a midnight snack!) Wish I could get my money back on that one, especially since she trashes Michael Mosley. Thoughts?

    • She applied for grant funding to study condensed-eating window (which she calls time-restricted feeding) in humans of 3–12 hours per day. I hope it’s approved and am very interested in what she find.

      As for food choices, I feel she’s very much wrong and that it is superlatively important to eat the most micronutrient-dense and -diverse diet [which has the benefit of being tasty since micronutrients include flavors!] viable.

      As for Mosley, well, apparently he interviewed her and, she feels, scooped her regimen. But he did make it less intense, and therefore not really her regimen anymore, and it seems to have helped a lot of people, so I have no problem with it personally. It seems to me she should do less complaining and more writing about her approach, plus make some improvements to it in terms of diet quality, as you noted.

      P.S. It’s “Krista Varady”.

      • Walter Bushell

        Meat is not a disease promoting food per your reference. Beef liver is perhaps the supreme nutrition dense superfood, for example.

    • Michael moseley stole her research… So i wouldn’t be trashing Varady… and btw calories in calories out!!!

    • Keep in mind her main point, though, which is that we’ll get benefits from fasting, even if we eat junk on our feasting days. I don’t think she’d deny that it’s good to eat highly nutritious foods on feasting days. She’s just saying that even if we eat at McDonald’s or some awful place like that when feasting, it won’t negate the benefits of fasting. This has been scientifically proven by now in many studies, so there’s no point in arguing with her conclusions.

      With that said, or course we can get ever MORE benefit by eating the most nutritious foods out there when we’re not fasting.

      Looked at this way, we might see four different LEVELS of fitness related to food:

      LEVEL 1) Eating junk WITHOUT fasting. (Poorest health)
      LEVEL 2) Eating junk PLUS fasting (a great improvement)
      LEVEL 3) Eating highly nutritious foods/organic/paleo, WITHOUT fasting
      LEVEL 4) Eating highly nutritious foods/organic/paleo, PLUS fasting (the best of all possible worlds)

      Varaday’s point is that FASTING is the most important factor, not what you eat. But if you combine fasting with superfoods, you’re on the way to optimal health.

  6. It’s worth nothing that Brad Pilon did his Master’s Thesis on intermittent fasting.

    Hearing the details about the 36- and 42-hour fasts was interesting. My own personal fasting regimen is:

    Towards the end of the day and toward the beginning of the [following] day, fast intermittently; and, once per week, FAST FOR A DAY [24 hours]

    So my daily fasting is variable, but my weekly fasting is a fixed commitment. By combining them, it often extends the weekly fast to 32–36 hours or so, similar to how you described above (in the 42-hour fast section).

    Seeing this post and your previous one about shorter fasts leads me to think my regimen is sensible and isn’t just some nonesense I made up. lol

    What I like about this combining two different fasting regimens approach is that the daily, variable fasts give me the flexibility to make sure it works for my lifestyle and even changing hunger levels, and the weekly fast ensures that I always have one significant, beneficial fast regularly. What’s more, I guess the shorter ones often are at least somewhat significant and beneficial as well—which is a good thing.

    Thanks for getting into details about these different-length and -frequency fasting regimens! They were helpful.

  7. Deb Griffith

    Thank you, Christoph! For her name correction! And your thoughts.

    It does seem to produce better results combining several methods, and/or switching things up a bit from time to time. Do you ever do a refeed day, one where you do no fasting or any calorie counting? I have to, for my sanity! I suppose it would be easier if there weren’t so many temptations out there. I work with several overweight men who constantly eat, take care of an elderly mother who loves her sweets ( though I got her off diabetes medicine a year ago through diet), not to mention just going grocery shopping! So much crap on the shelves!
    I was thinking, Dr. Fung should start a forum here. Seems like a lot of intelligent people comment.

    • I never calorie-count. Would never imagine doing calorie counting.

      As I said, I worded my regimen with one part, the weekly part, concrete (“A DAY”) and the daily part flexible (Towards the end of the day, and toward the beginning of the day…) flexible … so if one day I’m particularly hungry and/or something else is going on that it makes sense to me, I can wake up at 7:03 and eat at 7:42, figuring that I’ve delayed eating by a few minutes compared to what I could have eaten. And the same at the other end of day.

      This doesn’t happen often like this. I might instead wait until 3:14 pm, and just eat one meal.

      My point is that is flexible and variable for me, and that I’m simply delaying breakfast until I really am hungry and/or it’s convenient, and likewise trying not to eat too late at night. I’m not saying this is the end all and be all regimen. I’m saying that it fits in with lifestyle nicely, and that the variety of fasting lengths probably contributes something since it mimics the stochastic patterns of behavior and food availability found in nature.

      But in any case, I do at least one 24-hour fast per week, and often longer than 24 hours.

      • By the way, instead of calorie counting, a better focus is to get the most micronutrient-rich food per calorie.

        I don’t mean’ calculating this: I mean purposefully choosing the sorts of foods that are the most nutritious per calorie as a way to maximize one’s potential health. There’s a lot of science behind this. (Side note: Great website. Bookmark it.) I think you’ll get a lot more bang for the buck doing that than trying to figure out how many calories food items have in them.

        Which, incidentally, I bet you can’t do accurately unless you only eat packaged foods. Which would be dumb (no offense, and I’m not saying that’s what you do).

        And to throw a monkey wrench in it, you extract a lot more energy from most cooked foods than raw foods, but the calorie charts don’t reflect that. Way better off just fasting sometimes and otherwise choosing the healthiest foods that are viable for you most of the time. Further, that principle still guides you even when you don’t have the best foods available: it tells you to then choose the next best, most micronutrious foods, per calorie, that are available to you.

  8. I do “no food Mondays”, aka 36 hr fast. It has been a breakthrough experience for me. Eating mostly lchf already I never experience food cravings or hunger. Mental clarity, energy levels, general sense of wellbeing all enhanced. Back to lean college weight again 40 years after I graduated. I started doing this for hgh benefits since seniors tend to waste away and have seen superb positive impact in that regard. Obviously I’m endorsing the 36 bour once a week approach. -john d

    • While I realize you can see in my photo I’m still overweight, I’m significantly less overweight than I was when I started. I usually do my 24-hour (or longer) fast on Monday too … good to get that accomplished forthwith … and then do my variable fasts (really condensed eating window) on the other days.

      So yes, do the long fast, if doing it once a week, on Monday for the most part. Great idea! Plus there tend to be more social eating occasions toward the end of the week and weekend.

      • Awesome! No food Mondays it is!

        Here’s the crazy part: About 12 years ago I had liposuction to remove fat from my torso. I believed that was a sane thing to do!!!

        Of course it all came back more or less. Once LCHF lit up my life everything changed. Then IF with 8 hour food windows changed everything again. Then 36 hour “no food mondays” nailed this low energy/depression/moderate overweight middle aged spread thing once and for all. EVERY step has been a powerful force for health.

        Great to be a part of this. john d.

        • @John D I’m very interested to hear you had liposuction. I’ve always wanted to get it done on inner thigh stubborn fat. I will lose weight everywhere, face, chest, bottom and look gaunt and sick before anything goes off my thighs. Did the weight return to other areas instead of torso? I’ve heard people regain everywhere, even chipmunk cheeks but not where the lipo was. If I had the money I would def get it done.

          • I think it depends on your personal fat distribution and how well you maintain lower fat stores after the procedure. My wife had lipo done for her hips about 10 years ago and has not gained any fat there or in any out of norm areas. But…she watches her diet and tries to exercise on a regular basis (not that exercise can keep fat off as well as diet). She has friends who have had the same procedure and the ones who have continued to eat a fat producing diet have developed fatty deposits .
            Naturally, some “googling” to find some legitimate studies and info would help you decide.
            This may get you started..http://www.realself.com/question/lipo-fat-return-places

          • I know this is a late response but I read your comment and immediately wondered if you might have Lipedema? It’s a condition where fatty tissue develops in the lower body -but it’s not normal fat. If you tend to bruise easily or your thigh fat is painful, it might be worth looking into. Dieting won’t make it go away but manual lymph drainage can help and a certain type of lipo. Good luck!

      • Walter Bushell

        And hey, fasting Mondays, you can tell Ve*gns you observe “meatless Mondays.”

  9. ccavanaugh66

    Dr. Fung’s approach has helped me lose weight for the first time in 5 years, weight that wouldn’t budge with lchf alone. There are so many benefits to fasting vs. a daily calorie-restricted plan it’s hard for me to enumerate them. Main one is that I truly always felt like CRaP using that approach–weak, irritable, fuzzy-headed, depressed, hair falling out. Fasting and then eating to satiation produces the opposite state–I feel good, strong and clear headed, plus I lose weight a lot faster.

    Krista Varady writes that she puts people on 500 cals a day because she feared they couldn’t tolerate any less. But my experience is the opposite–eat nothing and your body adapts to fasting, produces ketones, and you’re running on rocket fuel.

    I was hoping this entry would talk about multi-day fasting, though, Dr. F. Is that one coming up?

    • Walter Bushell

      Belike Dr. Fung doesn’t want to advise multi-day fasting with out profesional supervision.

  10. Deb Griffith

    I agree. Dr. Fung’ s explanation of everything is the only thing that has made sense to me. And it so obviously works for so many of us. Sure, I am hungry in the morning….until work gets busy, and it’s hours later and I realize that I guess I really wasn’t. How can I be in my 50’s and just learning this?!

    • Cassandra

      Because everything we’ve been told about weight management for most of our lives has been unscientific lies? Healthy whole grains, eat frequently, everything in moderation, etc., etc.

      • Cassandra

        And don’t forget the biggest whopper–calories in, calories out. Then there’s eat less and move more.

        • The best one is to eat every few hours to keep your metabolism burning, keep BS stable and to stop starvation syndrome. It pains me to still read this advice being given out.

          • ccavanaugh66

            It does hurt to read it and remember the years I tried, to my detriment, to carry it out. MUST EAT BREAKFAST. Argh.

          • I did the 6 meals per day thing back in the eighties when I was training for Triathalons. I was always running, biking or swimming so I needed to refuel often (or so I thought).
            As I got older, I eased up on the long distance training and noticed that I was still hungry all of the time…..despite eating 6 times per day.
            My parents would eat three meals per day, no snacks and seemed to be fine. They never complained of being hungry and were lean (despite eating those horrible fats that my diet eschewed).
            It has come full circle. We find that their generation was correct. They ate two or three meals of meat, vegetables and some carbs and didn’t snack….other than special occasions. Very few of that generation were overweight, had type 2 diabetes, or felt food deprived.
            Then, along came the seventies and the new food pyramid….

    • Walter Bushell

      Fasting wasn’t out in the culture, instead we got eat every 2 hours to be sure your insulin doesn’t go low enough to allow fat to come out of the fat cells.

  11. The first time I saw Dr. Fung’s you tube video, I almost fell off my chair! I couldn’t believe that a medical doctor was telling the truth about the Diabetic Diet and was offering such a simple treatment solution for diabetes. I said in my heart, “This man is a national treasure waiting to be discovered.” (Yes, I did! …and to think he is a Canadian! 🙂 As a diabetic, I immediately recognized that this was the answer I have been looking for.

    While I completely understand and respect Dr. Fung’s cautions and warnings for diabetics not to fast without a doctor’s supervision, I have enough experience with doctors to know that trying to find a doctor to help you with a fasting protocol would be like trying to find a needle in a haystack.

    For the life of me, I do not understand why mainstream media is not banging down Dr. Fung’s door to interview him. We know from the mainstream media that obesity and diabetes are epidemic in Canada. Where is Peter Mansbridge? Where is Anna Maria Tremonti? Why aren’t there mainstream documentaries being produced on Dr. Fung and his fasting protocol for obesity and diabetes?

    I think that the only way to get doctors to change the way they treat diabetes is for the public to demand it. It is my hope that Dr. Jason Fung will one day be a household name.

  12. Deb Griffith

    Marie, you hit the nail on the head! I had the same reaction, and I have read his blogs at least 3 times all the way through. Then emailed him and thanked him.

    Then I emailed CNN, and suggested that Dr. Sanjay Gupta needs to do a CNN special report on Dr. Fung. This information needs to get out!

    Can you imagine the reaction from big pharma, corporate food giants, the medical community, hospital conglomerates, etc?! It would be a massive shock to the system, especially here in the U.S.!

    I went to a convenience store last night, and was appalled. (This is the usual scene) A very obese young girl and her obese mother were buying a box of cereal, a gallon of milk, 2 bags of chips and Doritos, and candy bars!! What is wrong with people?? It was all I could do to not say something to them!

    • Hi Deb,

      I think that you hit the nail on the head! 🙂 …you only need to follow the money trail to understand why the truth is being suppressed.

      Just yesterday, I was at my local coffee shop and met two nurses. I told them about this new diet I was following (LCHF) and then told them about the doctor in Toronto who treats diabetics with fasting. Well, in both cases, you could see the light bulbs go on. Immediately, they could both understand the value of such a regimen. In fact, one girl got so excited she started talking to me like I was medically trained giving me the science behind it. 😉 LOL

      Then she went on to tell me that her girlfriend was diabetic. She told me that her friend would not entertain such treatment. The nurse seemed quite disgusted that when she had lunch with her diabetic friend she had been eating a potato salad. I told her not to condemn or criticize her diabetic friends to me, because I knew that they were simply following the advice that their doctors, nurses and dieticians were giving them. I myself followed their “advice” since I became a diabetic. Although from the very beginning, I did question their diet, telling them that I would never lose weight with all those carbs that they wanted me to eat. But they told me that I needed to eat the carbs to keep my blood sugar level and to have energy. (Because of my other illnesses, I panicked at the thought losing any energy, so I dutifully ate my carbs at all my meals and all my snacks.) Ever since I had been on the Diabetic Diet I have had such problems keeping my blood sugar level. I could never figure out what I was doing wrong. And it caused me such severe stress to where at one point I was afraid to eat anything.

      That is why is LCHF diet is amazing to me. Since starting it about a week and a half ago, my numbers have been in range and level (and on the lower side, not the higher side of the range). I pinch myself every time I test, because I just can’t believe how quickly this turned around and how consistent my numbers are. And a huge bonus–even my husband has commented that he thinks I am getting stronger. And that is exactly how I feel on the inside, too. I mean, I still have a long long way to go. But I can’t tell you how thankful I am to be on this new diet.

      I noticed that on the Global News tonight they had one of their two minute news pieces talking about some researchers who were advocating the Vegan diet for diabetics. They were saying that it was even improving their nerve endings (I think they were referring to diabetic neuropathy). (I did try to find a link to share with you, but was unsuccessful in finding the story.) At any rate, perhaps there will be a bigger change coming if mainstream media will at least talk about diet alternatives for diabetics. While I did not fair well on the Vegan diet, I’m very happy for those who are. The thing is you do not want to have diabetes and all of the complications that come along with it. …and I personally do not believe that one diet fits all. 😉

      • Marie,
        My husband and I stuck to a strictly vegan for 2 years in order to reverse diabetes. It did NOT work for either of us.

        • I asked you this before, but you didn’t answer. What kind of vegan diet? What were the details? What did a typical, as opposed to ideal, day look like?

          The details matter.

          • Christoph,
            No eggs, no meat, no fish, no dairy.
            Vegetables, fruit and grain and nuts.

          • What about processing? That’s more what I’m getting at.

          • I don’t mean to come across as accusatory, Pat.

            I just don’t know what “vegan” means, so I was asking for clarification. Some vegans eat nothing but carbs, others eat a lot of process junk foods including fats and trans fats, others aim for high micronutrient density, some eat olive oil, some just get nuts and avocados for fats, some go real low fat, some try to eat a lot of fibre, and etc.

            It’s like saying one ate “omnivorous” to try and treat an illness. I would have no idea what that means.

            The McDougall plan and Fuhrman plan, to name two, are radically different. McDougall says you can cure diabetes with white rice and/or white sugar … whereas Fuhrman stresses fibre-rich, but especially micronutrient (as in phytochemical) rich food.

            Those are night and day differences. To use but one example, the most nutrient-dense fruit on the planet, amla.

  13. Deb Griffith

    Cassandra, I posted a link to this blog on Michelle Obama’s Let’s Move Facebook page!

    • ccavanaugh66

      Fantastic. Are we crazy to hope that the next administration will take this on?

      • ccavanaugh66

        replying to myself: yes it would be crazy to hope that. But maybe once the Obamas are out of office Michelle might get real about this and not worry about offending Big Food enough to speak out. Maybe…

      • I think there a lot of reasons we’ve gotten to where we are now. There’s probably more profit to be made in big factories pushing out things in bags and boxes on huge scales, and where the money is, unfortunately, that’s where investments will be made and political contributions are going to go. In other words there’s many people throughout the economy that are part of this, not just a few people in any particular political party, or industry.

        But I’m optimistic, I think the situation will change and in fact is changing a little bit now. I’m doing my part in a small way, I buy locally if I can and prepare more meals from scratch. Not easy if you’ve not done it before. It’s just I expect this process to be slow.

        • Walter Bushell

          There is definitively more money to be made in processed food, where you can get monopoly profits based on brand name. Only one company can make Snickers bars, for example.


          In contrast, pork bellies cost $1.20 per pound today.
          A pound of bacon costs about $5.
          That’s a 400% increase…

          …which looks like a lot until you compare it with 2700%-6400% for grains. Also, unlike grain products, bacon must be stored, shipped, and sold under continuous refrigeration—and it has a much shorter shelf life.

  14. Vince W

    Thank you for the incredible information Dr Fung! I read through Brad Pilon’s ESE material and found that it did wonders for my GERD. I discovered your site after the diagnosis of Type 2 (fasting BG ranges from 125-145!) I have stepped up the fasting from the 16 hr fasts to the multiple 24+ hr fasts, and was interested in your opinion of another intermittent fasting site run By trainer Matt Marshall, Fitness Under Oath. He says that 40-44 hr fasts are the best, due to the fact that this time period produces the highest levels of HGH and ketone bodies. He says the 48 hr+ fast tend to raise cortisol and tend to slow down fat breakdown. Comments?

    • I don’t believe there is a ‘best’ time. At 40-44 hrs, you probably get maximum HGH effect, but longer fasts do not raise cortisol. Longer fasts are more effective and more efficient, but everybody has their own preference for longer vs shorter. Both will work fine. If you prefer shorter, do it. If you prefer longer do it.

      • Dear Dr Fung,
        Thank you for six parts video on Obesity, I have learned a lot.
        What my query is, do we have to keep up with the Intermittent Fasting regime for life?
        to reverse Diabetes?
        What do we do when we go on holidays? Especially to Asian countries where Carbs are the daily diet?
        Please let me know.

  15. I like fasting from Saturday night till Monday
    And change my eating from noon to five or breakfast and dinner
    Glucose is better controlled with the 42 hour fast on Sunday
    And noon to five two meals the other days
    When keto adapted fasting is no longer hard

    • Hi Eric,

      What is keto adapted? Thanks!

      • It takes awhile to adapt to ketones as instead of glucose, a process that could be a few days to several weeks during which you might feel a little “not good.” For more info a good book is “The Art and Science of Low Carb Living” by Volek and Phinney. Or you could check out YouTube for lectures done by Stephen Phinney. The website DietDoctor.com is also a good source of LCHF information in my opinion and probably covers ketosis somewhere.

        • Hi Mike S,

          Thanks for all this information. I have never heard of Dr. Stephen Phinney before, but am impressed with his lectures and finding them helpful. I will try to find his book the next time I go to the book store.

          Do you know is the ketogenic diet the same as the LCHF diet? If not, what is the difference?

          • deirdra

            Ketogenic diets are LCHF, but not all LCHF diets are low enough carb to be ketogenic – you need to keep carbs below 20-30g.

          • Marie

            Thanks, Deirdra! I’ve been looking for over two weeks for this answer.

        • Jennifer

          Will going on LCHF help speed up the steps Dr Fung mentioned in Fasting Physiology part 2 as the first steps talk about glukos being released? If I have very low glukos levels to begin with due to eating low carb I think theoretically it should go quicker for me to reach the benefits of fasting on a shorter time period than someone eating carbs, or am i thinking wrong?

      • Blood ketones I. The .5 to 5 range. I try for blood glucose in the 60 to 80 mg/mg per dl and blood ketones in the 3mm range

  16. I love cream BUT have found not having cream reduces fasting bs and two hour pp about 4 mg per dl

    ZERO is the easy option. When keto adapted

    I think doctor ,V based her 500 to 600 option based on compliance research that does not apply or seem to apply to keto adapted people

  17. Dr. Fung, thank you so much for your detailed posts! I have a question regarding medication and fasting. I suffer from IgA nephropathy, and I am on 16mg candesartan. Stable with virtually no proteinuria and creatinine around 170. Do you see any issues with fasting given this? I do not have diabetes, but would like to try fasting to lose weight.

  18. Is there any research on the period of time that the body begins to use fat as fuel while fasting? I would assume that it is different from person to person but was curious if there was an average time that the body begins to use fat as fuel. I think knowing this, I would be able to optimize how long i should fast without getting excessive. I have heard 12 hours and 14 hours but nothing backed by science.

    • This book has a discussion of this:


      If you watch, you can get the book on sale for the kindle for not much money (I think I paid $3 for it). Unfortunately, the kindle for me makes referencing this kind of information (such as your question regarding how long it takes) hard. I refuse to use “notes” in the kindle, as then I can see what other people thought was important, which I do not care about. If I had the book, I’d just ear mark the pages.

      If you’re on a high carbohydrate diet, it takes much longer to get into ketosis when fasting, around 2 days I seem to remember. If you’re already on a low carb diet (but not in ketosis), it’s faster. If you’re using a ketogenic low carb diet, then there’s no time. So, it’s quite variable.

    • Erik, this is a very late reply and hopefully you’ve found your answer by now. But I just happened to listen to this lecture in which the doctor says 8 hours is the length of time you need to fast before your body begins using fat as fuel. It’s a great presentation, includes recent research, and is a topic we’re all interested in: “3 Ways to Improve Brain Function.”


      I’ve gotten so many great answers and links from the discussion on this page, I hope I can “give back” a little. =)

  19. Jennifer

    I just tried a 46h fast and it wasnt that hard, I even did a 1hour hot yoga class in the middle of it, it is very interesting to realise that I can function well without food. The only downside for me is that I love food and I dont have too much to do at work so I have had a lot of time thinking about eating. I wasnt hungry but I missed eating for the taste of it. I have tried 24h (easy) and 36h (also pretty easy), up to 40 hours is easy for me, I’d say anything longer than that would work well as long as I’m busy so I forget to think about eating.

    • Jennifer

      (And for anyone interested) during my 46h fast I lost 1kg (and another 0.6kg this morning, even though I had a huge dinner when breaking my fast last night). Will be interesting to see if the weight changes (up or down) tomorrow morning after two healthy size LCHF meals today). Also worth mentioning I’m not overweight (170cm 65kg), just want to lose the last 4-5kg stubborn ‘cosy weight’. And I eat 16-8 every day, dont even count it as fasting anymore as it’s so easy. a black cup of coffee with cinnamon is my morning treat.

      • Those last few kg can be tough since the body desperately wants to hold on to it …just in case you get snowed into that cave and have no fresh mastodon or berries to eat. It seems to me, that if you left the safety of the cave. even though you’ve not eaten in 36 hours or so and tracked down and wrestled with a mastodon, that your body would be inclined to want help you out by giving up some of that stored energy from those stubborn places.
        If you don’t have a mastodon handy, you may want to consider two HIT workouts per week. (if you are normally healthy)
        Just a thought. It takes a lot of patience and some exercise (to keep the muscle mass) but the fat will come off…..s l o w l y.

  20. 6 months ago my a1c blood test was 9.3. Using Januvia, 3 months ago my a1c was 8.5. Today after diet & fasting a couple of days a week and no diabetes medicine, my a1c test was 7.3. Thanks Dr, Jason Fung. I feel that my life expectancy has increased tenfold by following your advise that’s in your blog.
    I wonder what my doctor will say to me at my next appointment. I’d love to have Dr. Fung as my doctor but I’m here in San Diego. I like you from your videos and from the results I’ve had from your ideas. Thanks again

  21. Deb Griffith

    Nice going, Jennifer! I’ve never done 46, but do 36 three times a week (fast beach diet), plus 16:8 every day, except Saturday. The weight just melts off, literally!

    Picking your brains here, I really feel pretty strongly that we need to get the word out to our communities, but how? I see so many obese people every day, and I feel like I have this HUGE secret that will help them! I want to see someone in authority on this hold seminars or something. I want to make signs and put them up at busy intersections that say “I can make you skinny and healthy!”. I have posted links on Facebook, written CNN,…..any ideas??

    • Jennifer

      Thanks Deb! Wow 3x36h per week, that’s hard core! In regards to coming up with a way to communicate to the world how good this is I dont have any ideas unfortunately, the most efficient would be if BBC or any other channel would agree to do another documentry about it, after the BBC documentry on 5:2 aired there was a HUGE response in media and people tried it with some success, although unfortunetaly it was somehow OK to eat 500kcal on the fast day (and they could be spread out during the day, losing the majority of the benefits of fasting). Another way would be to get a celebrity onboard, if Kim Kardashian said she lost 10kg by fasting, 20million people would most likely give it a go. Is there anyone here that knows Kim? 🙂

  22. deb griffith

    Really, you are so right! We need celebrity endorsement! Alas, no Hollywood or otherwise famous connections here!

    I was hoping that Dr. Sanjay Gupta at CNN would see my email and get on it. If that man can change the world’s opinion on medical marijuana, he can do anything!

  23. deb griffith

    I did a fast day yesterday. I usually eat a few whole wheat crackers or an apple to get through the first 16 hours but yesterday I easily went without. I chewed gum (a fresh piece every hour or so), which got me to wondering what role saliva plays in body chemistry, as it relates to insulin/glucose. And found an article that it does indeed play a role. interesting!

    • Jennifer

      Hi Deb,
      I think in one of Dr Fung’s old posts about sweeteners and insulin research showed that washing your mouth with a drink containing sweetener (don’t remember which one but not normal sugar) and then spitting out increased insulin, so chewing gum with sweetener is maybe not the best. However I have no idea what affects insulin the most, chewing gum or crackers (if you absolute need something other than water and tea/coffee).

      • I had just read on Mark Sisson’s blog that research shows Stevia as a sweetener that lowers insulin levels. Of course, I tend to take these studies with a grain of salt but would be interested in what Dr. Fung says about it.

      • Deb Griffith

        I do remember reading that, Jennifer. I try to cut it out of my coffee but it just doesn’t taste right! Also just bought some fruit flavored sparkling water…0% everything…I was happy! Until I read the fine print…Yep, aspartame! I will get stevia.

      • Deb. You may want to try the BulletProof coffee to get you through the firs 16 hours. When do you start your fast?
        I find it easier to start a fast right after the evening meal..which gives you about 12 hours of fasting…8 of that asleep, so it’s not bad at all.
        If you begin at say..7pm and go to bed at 11, you will have knocked out the toughest part (at least for me). If I’d had a fatty meal the night before, I don’t have much hunger in the morning..though I used to when eating lots of carbs at dinner. Have your morning coffee….as BulletProof coffee and that will keep hunger at bay for quite a few hours. Have some more (decaf works well as does hot tea) at around 2 pm and you’ve just blunted your appetite some more. Before you know it, your 24 hours is up and it’s time to eat dinner.
        I’m experimenting with a few 36 and 42 hour fasts and find that it’s not that difficult as long as I use the BulletProof coffee or similar. The biggest challenge I have is not the feeling of hunger but the feeling that I get about ‘having to eat’. I don’t have to but my brain still tells me that “we always eat now…what’s the holdup?”
        I wish you well and you may want to research that Stevia question before loading up on it.

  24. deb griffith

    “Not all people are the same in their ability to handle starch,” said senior author Paul Breslin, Ph.D., a sensory geneticist at Monell. “People with higher levels of salivary amylase are able to maintain more stable blood glucose levels when consuming starch. This might ultimately lessen their risk for insulin resistance and non-insulin dependent diabetes.”

    • This human biological diversity angle makes perfect sense since amylase does vary and our ancestors ate more or less carbohydrate depending on many factors, especially latitude.

  25. Deb Griffith

    Yes, Christopher, I imagine that, besides the “controllable” things in our diets, there does have to be some genetic differences, albeit ones we can overcome or at least work around!

  26. Deb Griffith

    Erik, if you see this, I am reading “Good calories, bad calories”, and found this :

    (comparing ketosis to ketoacidosis) “…..compared to the 5mg/dl let one levels that are typically experienced after an overnight fast -12 hours after dinner before breakfast – and the 5-20 mgs/dl let one levels of a severely carbohydrate-restricted diet with only 5-10% carbs.”

    This book is amazing! I can just picture all these drs and corporate types plotting to keep us fat and sick. I am so disgusted with them, and so happy to have found a way out from under the madness!

    • Deb, “Good Calories, Bad Calories” is a real eye-opener, a book I have returned to again and again for inspiration and info.

      As far as “fat and sick”, industry doesn’t really care if we’re fat and sick, or thin and healthy, they just want our money.

  27. Daniel Flichtentrei

    Dear Jason: I am cardiologist from Argentine I want to consult you on a 65 years 2 diabetic insulin and incretin, visceral obesity (100 kg waist 120 cm ), hypertension and chronic renal failure with creatinine of 2.8 mg . No weight loss with low carbohydrate diet (only 2.5 kg) in 3 monthes although greatly improved blood sugar control . What are the risks of intermittent fasting ? Renal acidosis ? What is the best program five days and two days ? Thank you very much , I learn every day of your lectures and texts that I thank you .

    Dr. Jason Fung: I don’t have a ‘best’ regimen. In our IDM clinic we individualize the approach. Some like frequent short fasts, and others like the longer fasts. Some people get better results with one or the other. This series goes over some of the different regimens available.

    • One of the reasons I looked into and then started intermittent fasting is that I lost about 20 pounds (say 10kg) on low carb, but then stopped losing. I was eating 4-6 meals a day. I am insulin resistant but not diabetic (HbA1c of 5.4-5.6, fasting blood sugar 103/102/92 for last three years of once-per-year test). It was not until I started intermittent fasting that I restarted weight loss, though I have also increased my fat content and decreased my protein content at the same time.

  28. Dear Dr. Fung Can u tell me , how the the insulin sensitivity increase with fasting. What is the scientific explanation behind that? Further can someone continue with normal food( carbs) after they got cured by fasting? And normal procedure is to increase insulin throughout , how the recepters are responding when u increase the dosage?
    Like to hear from you soon. Further ur presentations make sense. Good work

    Dr. Jason Fung: Prolonged periods of low insulin levels prevent the development of insulin resistance. Increased insulin will lead to worsening insulin resistance. Decreased insulin will lead to insulin sensitivity.

  29. David Carter

    My wife has Hashimoto’s, and I’ve read that no one w/ Hashi’s should fast. What is your experience in this area? She takes MetforminER, 500mg, 2 x 2. Tnx, and great series!

    Dr. Jason Fung: I can’t answer personal medical questions unfortunately. You need to consult your physician

  30. Does 22-24 hours daily fasting have any bad effects? After trying the 1-day (22-24 hour) fast for twice a week for 2 weeks, I found that I like it so much that I prefer to be doing it everyday. It also saves so much of my time – no more hectic mornings deciding LCHF diet-friendly food, cooking, packing breakfast and lunch boxes for myself plus the extra hour that I get at work. Not to mention the awesome energy throughout the day. I just eat when I get back home at around 5:30 or 6pm. And after that I do not eat anything more.

    My dad used to do something similar for many years when he was working. He used to eat breakfast at 6am had a very late lunch at around 5pm when he returned home from work. So there was always a 11 hour break between his breakfast and late lunch. But he developed diabetes at the early age of 40 though he was never fond of processed foods, sweets, candy or chocolate. Most of his meals were home-cooked by mom and mostly carb based along with meat/fish/vegetable side-dishes.

  31. What an amazing read. I watched Eat, Fast, Live Longer and started my 3 day fast on Monday at 9pm and ended Thursday 8am, 83 hours. I was amazed how good I felt and how few times I thought of food. My tummy grumbled a few times but I had a peppermint tea and that fixed that. I also had the Miso soup in the evening. I have eaten a lot less since yesterday as well as I’m just not hungry. I’m very pleased to know that I can NOT eat anytime and that instead of what we have always been told, I will actually be helping and healing myself. Thank you so much for all your fascinating and eye opening articles.

  32. Christoph Dollis,
    I did not eat processed foods but did eat some refined wheat products – white flour and pasta. But mostly my grain choices were whole grains. this is when I was vegan for the two years. Also this was the pattern when I was not vegan. Living close to and working with Seventh Day Adventist Church people is where I learned about vegetarianism and vegan diet and got many recipes from these people. I was a Public Health Nurse and taught people about healthy diet and myself ate one, according to the nutritional guidelines of the day. When the new guidelines came out I was not in favour of the increase in starch consumption recommended. Thankfully, my job had changed and I did not have to give this advice.

    I do not follow this posting, so do not expect me to answer questions. This explains my not answering you sooner. I hope this answers your question to me about my vegan diet. Sorry that I will not be following the post for further conversation. Truly, I am more interested in following Dr. Fung’s approach to diabetes treatment than the vegan diet. Been there, done that, got the t-shirt. As I said, it did not work for me. Dr. Fung’s approach has been tried and true – my husband has Blood sugar of 5 without any medications anymore.

  33. Just wondering, I live in Windsor, Ontario and am interested in this solution to insulin resistance. Is this diet available from a doctor in my area? Thank you!

  34. Dr. James Johnson also wrote an interesting book called The Alternate Day Diet which I highly recommend.

    Thanks for this series on fasting!

  35. Is it safe and/or recommended to do sustained/intermittent 36-42 hour fast with just one feeding day in between if i am attempting to lose a large amount of weight? My blood markers are all OK per my last physical and no medications are being taken just a prolonged bout of obesity at 54 years old.

  36. I have been on the lchf for two weeks now and my bs has increased to 10.4 mm/ol from 7.4. What could I be doing wrong?

  37. Danielle

    Is red wine insulinogenic?

  38. Dear Jason Fung, Do you have an opinion on Dr Bert Herrings “Fast 5 Diet” especially with regard to type 2 diabetes?

  39. How frequently do you advocate people do the prolonged (>=36 hour) fasting intervals for? In terms of number of times a week and for how long? Thanks

  40. Glad to see someone mentioned doing a 42 hour fast and then 16/8 the other days. I’m doing a 44 hour fast (Sunday 8p to Tuesday 4p) and then 16/8 the rest of the days. I work night shift, Tuesday-Friday, 730pm-6am. For workouts I’ll be doing Tabata Style/HIIT, 3 times a week and daily walking of my pups. I’m 5’2″ and 151 now. Hope to get to goal by my birthday in February.

  41. […] peruuttaa T2-diabeteksensa ruokavaliota muuttamalla. Lisäksi hän noudatti kehittämäänsä 5:2 paastoa. Paasto on tehokkain tapa vähentää sisäelinrasvaa. Se myös lisää lihaskuntoa parantavien […]

  42. […] Longer Fasting Regimens – Part 7 […]

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