Fasting-Mimicking Diet: Can You Make it a Habit?

I was glad to see Valter Longo’s Fasting-Mimicking diet in the news again this week.  I have been enthusiastic about Longo’s work ever since he documented altruistic suicide of yeast cells for his PhD thesis in the 1990s. Programmed death in one-celled protists was considered an affront to evolutionary theory at the time, and he had a devil of a time getting his findings into print.

Longo discovered in 2002-2005 that fasting had a powerful benefit for cancer patients, and that in conjunction with either radiation or chemo, it greatly magnified the benefits while mitigating the side effects.  Intermittent fasting had benefits, too, for the general population, independent of cancer.  It seems to be a way to get the health benefits of caloric restriction and it is easier to stick to for many people than a consistently low calorie diet.

But Longo couldn’t get either doctors or patients interested in the fasting program.  Part of the problem was the toxic mix of capitalism with medicine: the US relies on testing and promotion by profit-making companies to push medical technology forward, and fasting isn’t a product that anyone can make money on.  There was also an emotional truth: cancer patients feel scared, beleaguered, emotionally drained.  So much is dragging them way outside their comfort zone that it takes extraordinary strength not to fall back on food as one of life’s most reliable comforts.

So many medical researchers see their job as finding treatments, and leave the problem of adoption and compliance to someone else.  But Longo set himself single-mindedly to the task of bringing the benefits of fasting to a wider swath of the population.  The question that led to the Fasting-Mimicking Diet (FMD):  What dietary regimen can provide the greater part of the benefits of a water fast while inducing less hunger and minimal disruption to concentration, vitality and the pace of life?

I have done about 9 cycles of the FMD over the past 1½  years, including this week.  In my personal experience, 5 days of the FMD is eminently tolerable once I begin, though I still face resistance when I think in advance about disrupting my comforting food routines.  (Yoga, swimming and meditation have the same barriers for me–difficult in the anticipation, enjoyable once I begin.)  For me, FMD is not a weight loss program.  I gain back all the weight I’ve lost within a week after the 5-day program is finished.  Others may have different experiences.  People have used the 3-meal version of FMD (3 meals at 360 calories) as a medium-term weight-loss program, but the protein content is probably too low for those concerned about maintaining lean mass long term.

In his new study, 100 participants were randomized into two groups.  The first group did three rounds of 5 days on FMD over three months.  The second group did nothing special for three months, but were given an opportunity to try the same three rounds during the following three months.  The average weight loss was 6 pounds for those who completed all three cycles; lean body mass was lost, in the same proportion as fat.  Blood pressure, blood sugar, triglycerides all improved on average, and C-reactive protein (an inflammatory marker) went down as well.  

The study included a range of healthy people as well as people who carried more weight and had higher risk factors.  It was those with the higher inflammation and blood sugar who realized big benefits from the program, and the already-healthy were averaged in.  There is a lot of evidence to indicate that intermittent fasting works, and that the FMD delivers similar benefits.  But if you’re already lean and healthy with low blood sugar, then it’s less clear whether there are substantial additional benefits from intermittent fasting.

Notable was a reduction in the hormone IGF-1, which I don’t necessarily regard as a good thing.  On the one hand, lower IGF-1 is characteristic of all caloric restriction models, in animals and humans, in which life span is increased.  So it is an indication that the FMD was effective.  But low IGF-1 has consistently been found to increase risk for all-cause mortality, and heart disease in particular [ref, ref, ref].  Benefits of higher IGF-1 include maintenance of muscle mass and growth of nerves that diminishes with age.  

An additional benefit documented in the past is a “reset” of the immune system.  The white cell population is pruned during fasting, and the most-needed naive T-cells regrow after eating resumes.

Antidote to Obesity

It’s the (large and increasing) population of unhealthy people that Longo is targeting.  There is every reason to expect substantial benefits, but the big issue remainss: how many people can be motivated to take up the practice and stick to it?  The question was touched on only peripherally in the current study, without discussion; of 48 subjects selected for the first round, 39 stuck it out for three FMD cycles over three months (81% compliance).  That’s encouraging, but what we really want to know is: how many people will actually modify their eating rhythms for years at a time?  Will they feel the benefits and will that motivate them to stick with it month after month, five days each month?

And will this translate into long-term weight loss?  Sustaining weight loss is notoriously difficult for about 95% of the population.  People can stick to a diet for a time, but the Siren song of food is with us everywhere, and sooner or later we succumb.  Fortunately, there’s good reason to hope that the FMD discipline offers benefits even if weight loss is not sustained.


How to do it

Longo’s own company, L-Nutra offers a packaged diet, called ProLon, availble through health care professionals.  It’s pricey and may be covered by insurance.  LifeBox offers a non-prescription alternative that is not as much cheaper as it might be.  For my own experimentation, I have preferred to use fresh, whole foods approximating the same macronutrient proportions as the ProLon package.  It requires some time and attention in food prep, but it costs less than you’re currently spending on the same meals, and you can fill yourself with satisfying portions of fresh vegetables for the same 360 calories.  Here is my page of instructions and advice, with recipes designed by Enid Kassner.

For many of us, our relationship to food is central to our psychology.  Shaking up food habits disrupts everything else as well.  It’s the main reason that food habits are so hard to change, but for me, it’s also a good thing.  I enjoy the challenge and the self-awareness that come from a new frame of reference; fasting changes my perspective, my emotional baseline, and my mental state.  For me, the first day is unfocused, low energy, but often a time of creative new ideas; the second day is distracted, obsessive, sometimes headache-y or otherwise uncomfortable, and beginning with the third day there is returning energy, along with a freedom that I didn’t know I missed.


Why is life expectancy in America lagging?

Part of the answer is certainly cultural.  Advertising, parties, lunch and dinner meetings often reinforce consumption of food that is designed to be addictive for the sake of corporate profits.  In America, we are surrounded by overweight people, but France and Italy have much lower obesity rates, and you can walk all day around the cities of Japan or China without encountering anyone who is seriously overweight.  Even in America, the problem has grown way out of proportion only in the last 40 years.  This and income disparity are the main reasons that life expectancy in America is at the bottom of the developed world.  Our unaffordable, dysfunctional healthcare system provides many additional reasons.  Meanwhile, life expectancy in Asia is climbing at an exemplary pace.

Longo’s FMD is designed to address this most accessible factor in the diseases of late life for a large swath of people who find they cannot lose weight.  His research is based not just on effectiveness but equally important on tolerability.  How many people will adopt it and reap the benefits?  This will be an important question for public health going forward.  But you are a unique individual, not a statistical median.  I encourage you to experiment with FMD, see what you learn about yourself, and decide if it can be a valuable part of your health program in the long term.

77 thoughts on “Fasting-Mimicking Diet: Can You Make it a Habit?

  1. I have been doing Intermittent fasting for 2 months now. 5:2 method. Two days of not eating for 20-24 hours. I have seen very limited weight loss and no real fasting blood sugar lowered yet. Which were my reasonsI I am 50 lbs overweight. I am planning to stay with it but looking for methods to complement how I eat on the 5 days. I don’t feel well when eat too much protein, crave salads and veggies, but that is recommended by many diets. I eat no sugar or grains, but I do eat healthy fats, seeds, nuts, eggs, raw cheese etc. Looking for better resources on how to eat when not fasting to support faster and lose of belly fat. I also do long walks and weight training already.

    • Hi CSanford wanted to see how your experience was on the 5 day FMD. Sounds like you’re doing the right things! Keep at it buddy. I’m curious what both your eating time window is like on the 5 regular days of 5:2. Is it intermittently fasted? Also, the long walks and weight training are good. As long as you are getting some sort of “sweat based” workout in lets say a TWO times a week. Maybe one day where you combine weight training in a high intensity fashion, and another day where you do some sprint work in a Tabata fashion. Tabata workout typically is only 4 minutes long, but hard!!.. Try something like uphill sprints, mountain climbers, or simply fast paced walking for 20 second period, rest 10 secs, do another 20 secs, 10 seconds, etc until you hit 4 minutes. Interested to hear more about your journey!

    • Have you looked into thyroid function? Also, I find that doing a daily 16 hr fast can be more beneficial than doing 2 days of full 24hrs.

      Hope you’ve come through that challenging period since you wrote this comment initially.

  2. Josh,
    I’ve done FMD twice in the last 2 months. I’ve also withheld food except for pats of salted butter or small chunks of Cheddar for 3-4 days to speed recovery from a cold, probably twice a year. Also weekly IF.
    I think that it’s eminently doable.
    In my experience it’s even effortless if your eating style is ketogenic. KD prevents loss of muscle mass.

    • KD = ketogenic diet?
      At 59, I don’t want to lose muscle mass any more than is inevitable. I am not overweight, and stay fairly active, so I’m mostly interested in the FMD for quality of life.
      Can you recommend a website to learn about this? Are there some of the recipes at FMDRecipes more “ketogenic” than others?

      Thanks for your work!


      • It’s a question to which we only have incomplete answers. A sensible approach is to raise protein intake (but not above 100g/day) supplement with creatine, and use resistance training and saunas to increase your IGF-1 levels. Then if you take a 5-day hiatus for a very low protein FMD, your muscle mass should come back promptly when you re-feed.

        • Hi Josh, one finding of Longo’s research was that high IGF-1 increased risk for cancer for folks between the ages of 50 and 65. So lowering this hormone is not always a bad thing for some age groups. Peri menopausal women are also at risk for breast cancer with high IGF-1.

          • I’m aware that there are pluses and minuses to IGF-1, and that it probably depends on your situation and individual metabolism. I suspect that bursts of IGF-1 are good and chronically-elevated IGF-1 is bad.

      • It is totally inevitable – all you need to do is lift wieghts 2-3 times a week. The work out should be progressive and all you need to fokus is that you use the whole og most ofte body, like squats, deadlift, if done correct you will feel results within just 14 days 🙂

  3. Fasting isn’t a new concept for health benefits. I was water fasting in 1977 based on Arnold Ehret’s book, Rational Fasting. Then later in years I swapped to juice fasting based on Paavo Airola’s work. He says in his book that fasting has been used in many European health clinic for years. Not sure when he wrote the book but I would have read it in the eighties. The Gerson Clinics use juicing and fasting to heal cancer with a very high success rate.

    • NIH sponsored trials of the Gerson Therapy had to be stopped early because participants assigned to this group were dying at a much higher rate then those receiving a conventional treatment. They were dropping like flies. Their claims of success are based on ignoring failures, unlike the FMD trials which were all carefully controlled with results thoroughly documented. The same can be said for many other claimed natural cancer cures, which the NIH has disproven. You can see the results from a PUBMED search.

  4. Josh, thanks for all of the great material!

    Over the past 6 months, my usually robust schedule has suffered a major setback due to a family matter out of state and a hand injury… Prior to the setback, I was around 15 lbs lighter.

    I am hopeful that I will be finished with the hand injury next week & I will begin to get into a reasonable regimen again. I am 69, take no medications and, as far as I know, have no health conditions except sleep apnea for which i use a c-pap. I would like to lose 32 lbs.

    My eating regimen will be a modified keto. I will resume doing a 90 minute hot yoga on Tuesdays and Thursdays. I will resume cardio combined with light weight workout on Mondays and Fridays. I will, for the first time, endeavor to do a weekly, one-day fast by not eating after Wednesday until Friday morning. Will evaluate bi-weekly and make adjustments.

    If anyone is interested, will be happy to share results. Otherwise, I’ll post when I’ve hit the goal. Any questions or suggestions from this erudite bunch will be much appreciated! Thanks.

  5. I find fasting very difficult and many women do.I find my metabolism slows, I get cold and very tired. Also I have Gilberts syndrome and fasting is not good for this. Therefore it is a revelation that a low calorie diet for 4 to 5 days will produce the same results without so many of the disadvantages.

    I have been very interested indeed to read about Valter Longo and the fasting mimicking diet and I am very surprised not to have read far more about this. I Think that his product is vastly overpriced and not very interesting as well as being easy to reproduce at home.also I don’t care for his nutrition choices and I think the recipes offered here are far more healthy and beneficial. It does occur to me that the famous cabbage soup diet, which takes a week and basically comprises eating cabbage soup during the week, is very much like this. Although the cabbage soup diet is much derided when used for a fast weight loss programme, it does seem to me that such are use of vegetables for a restricted calorie intake, for a 4 to 5 day period is very similar to what the fasting mimicking that provides.

  6. The comments about IGF-1 and the 3 references are extremely puzzling. Note that Cynthia Kenyon who did huge amount of work with C.elegans involving doubling their lifespan called DAF-2 which is equivalent to gene encoding IGF-1 in mammals, “the grim reaper gene”. So hard to figure how “the grim reaper gene” becomes a good thing.

    • It’s not true that DAF-2 is the worm version of IGF-1. Worms have their own IGF-1, and DAF-2 is a receptor for it. DAF-2 senses IGF-1, and inhibits DAF-16 (via phosphorylation), and it is actually DAF-16 that turns on the genetic switches to put the worm into a long-living mode. So low IGF-1 dials down DAF-2 activity, which turns up DAF-16 activity. Humans have analogous pathways (FOXO=DAF16), but they are not triggered directly by IGF-1.

      It’s even more complicated in humans than in worms. I think we have to consider the epidemiology of IGF-1; low IGF-1 is a mortality risk, but high IGF-1 is not. My best guess is that low IGF-1 is a marker for calorie-deprived state in the body, but it is not a direct driver of life extension pathways. If you have better information, please let me know what I should be reading.

      • Hi Josh,

        “Daf-2, Wikipedia”
        “The DAF-2 gene encodes for the insulin-like growth factor 1 (IGF-1) receptor in the worm C. elegans. DAF-2 is part of the first metabolic pathway discovered to regulate the rate of aging. …”In a 2007 episode of WNYCs Radiolan, (Cynthia Kenyon called DAF-2 “the grim reaper gene”

        IGF-1 Signaling pathways:
        A discussion about how DAF-2 is well conserved, and is IGF-1.
        Knock-down of DAF-2 results in activation DAF-16 and up regulation of about 100 genes for cell protection and longevity.

        “By silencing DAF-16 activation of DAF-2 receptors can ultimately compromise a cell’s ability to mitigate harmful enviornmental consitions.”

        “In most eukaryotes, insulin activates DAF-2 signaling.”

        Diet’s interaction with the IGF-1 pathway:
        “Wild type C. elegans fed 2% glucose showed reduced DAF-16 activity and lifespan was shortened by 20%.”

        So low calorie diet, lower IGF-2 and increased life span is what is expected.

        What is very hard to understand is the references with no explanation of activation, signaling pathway, upstream, downstream, just a lab finding of low IGF-2 and decreased survival. That is extremely hard to explain.

        But saying IGF-2 is not equivalent to what Cynthia Kenyon called “the grim reaper gene” does not explain the apparent paradox.

  7. Hi again Josh. I’ve been doing a 5/9 water-fasting routine for the past year, having been fasting in other configurations for the three years prior to that. I fast from late Sunday night to Friday evening, every other week. My wife does something similar, although slightly less strict.

    I’m not sure I’d class it as a habit; more a discipline perhaps, though I don’t find it terribly hard now. I get slightly tired on day three, but after that I’m fine. And I rarely, if ever, feel hungry.

    Weight has never been an issue for me – been pretty constant at 10st / 65kg since I was 18, about thirty years ago. I think, but am not certain, that my BP and heart rate are lower than they used to be. I have a suspicion I get colds less often and recover quicker than I used to, but I can’t be sure.

    I have a vague plan to write an app to let people record their fasting activity, in order to generate data for some future research project by whoever. If there were a cheap ageing biomarker test (I’m not aware of one) we could generate some interesting data, and maybe prove whether fasting in humans does actually slow ageing. I’ve recorded all my fasting since I started 4.5 years ago in google calendar.

    Anyway, happy to answer any questions anyone might have.

      • Sure Kevin. There’s not a hell of a lot to really. From waking up on Monday morning until getting home from work on Fridays, every other week, or sometimes with a two week gap if there’s some big social thing on, I don’t eat anything.

        I drink lots of black tea/coffee, and very occasional diet drinks. Besides that nothing.

        When I start eating again I don’t do anything special like east sparingly for a while. Just normal food. I try to make sure I eat a decent amount though. Mostly via large packs of peanuts 😉

        I recall feeling slightly awkward among friends/colleagues when I first started fasting (I did 48 hour fasts initially four years ago). But it’s easy now because everyone’s used to it. And of course I get lots of “you do WHAT???????”, which I have stock answers for now.

        Actually lots of people I know have started some sort of fasting themselves because of my going on about its possible health and longevity benefits.

        BTW, does anyone on here know of any decent cheap ageing biomarker tests that exist now, or may exist soon?

        • Certainly, a lot of health experts would caution you on such protracted fasting. The amount of gluconeogenesis that is required under this routine would be phenomenal. Such protracted fasting and the gluconeogenesis spike that comes with it, can and will place tremendous stress on your HPA axis (increased adrenal activity) with surging cortisol levels all along. This is rarely a recipe for longevity, especially if you combine this stress to your system along with the stress of working in a busy society. I wish you well of course, but all this sounds like a recipe for “crashing” at some point in the future.

      • Through bluegreen’s information is also useful? I find that I eat less now I’m older anyway and a low carb diet helps hugely. If I’m not hungry I don’t eat. Unlike when I ate high carb, I find that I respond to stress and viral illness by losing my appetite, which I now consider to be a benefit and I watch out for. Also, significantly for me, I no longer comfort eat and that, amazingly, requires no will powers whatsoever.

  8. Hi Josh,

    The situation you described with IGF1 and IGF-BP is so baffling to me can only be explained by two different pathways and negative feedback loops.

    One explanation is cell stress stimulating Rtp801 resulting in blocking mTOR and very low IGF1 and IGF-BP and failure to phosphorylate Akt and failure to phosphorylate Foxo3 resulting in failure to suppress BAD and apoptosis causing sarcopenia and heart damage and increase risk of death.

    In total separate pathway have caloric restriction lowing mTOR and having lower IGF-1 and usual life extension pathway.

    Maybe not the right explanation; but works for me so your very baffling finding and references will at least not keep me up all night.

  9. I can comment about my own experience here. I’ve been doing IF for the last couple of years : one meal per day, mostly low carb high fat. I lost some weight (I’m 67 kilos for 1m70 down from 72 and at some point 82 but this was a long time ago). I like this because it’s … very practical ! I’m an endurance runner and I’ve been doing my training sessions in a fasted state with zero issues. I got interested in longer fasts, because of Valter Longo and information found about the use of long fasts in eastern europe at the beginning of the 20th century to treat all types of diseases, including depression and other mental health conditions. I’ve been doing 2, 3 and 4 days fasts and it’s easier than I thought; the social component is the most difficult, so some weeks the only meals i have are when i have dinners with friends. Hunger is really not a problem if you are in a non stimulating environment (ie no tempting food in sight). In that regard, the last book of Stephen Guyenet, the hungry brain, is very enlightening. The brain reacts to all possible cues : visual, olfactory etc – fasting helped me notice that – if I see someone eating, i want to eat. I’ve been exercising at the same time with no issues. What i find interesting is the link with the ketogenic diet – fasting is the fastest way to get into ketosis (pun intended). After 2 or 3 days i’m often at 4 or 6 mMol/l and I noticed that my blood sugar can go very low (0,5 g/dL) which is technically hypoglycemia but the ketones are working well as a replacement fuel and my brain is just fine – actually better, as I experienced better focus and productivity on the 3d and 4th day of fasting. I’ve seen studies showing that muscle mass does not really decreases, once the body is in full ketosis protein is actually spared – and the same pattern also happens in animals who can fast during very long durations (penguins and migrating birds for instance). It’s very interesting to get some “distance” with food, it’s actually liberating and then when you see the amount of time and mental energy required to have 3 meals a day you realise how demanding it is ! Regarding your post – I wonder why Valter Longo needs to offer food for dieting, it’s kind an oxymoron to me (but probably a way to make money). And the IGF-1 decrease, that I never heard of before, is a little bit worrying. I’d love to know more about that. A good recent reference on fasting is Jason Fung’s last book – he uses fasting to treat diabetes and seems to be pretty successful.

    • Hi Philippe, Your quote on “get some “distance” with food” resonates with me. Yes, food was like air bubble, astronaut helmet on my head; something I dare not take off or risking death. After 5 months of 2, 3, 4 and 5 days water fasting and IF (18/6) most days, I am taking this helmet down and breathing fresh air. I am aware when, what and how I eat. I could almost hear the sound of people savouring their foods when I walked into food court. I have a new relationship with food, one that is “distant” (your word), one that is observable and one that is less submersible. This is the spiritual dimension of fasting.

      • Also the spiritual dimension of eating, that is, bringing awareness to the act. Is the food eating us, or are we eating the food? Conversely, our practices may consume us: are we doing the fasting/dieting, or is the “practice” doing us? That’s okay too, but the one is, I think preferable to the other, or at least has a more expansive range of benefits.

  10. It is only becoming more and more difficult for people to think about fasting, or even food reduction, with the explosion of food shows and channels, and chefs getting treated on these shows as if they were heroes of the world. You want adventure? It involves eating some exotic, greasy, concoction of animal body parts laced with oils or dairy fats. Thanks a bunch, Anthony Bourdains of the TV world. While the odd chef like him seems able to keep his weight in check, his followers are becoming more obese and sedentary, no doubt.

  11. About 30 years ago I twice did 4 day water fasts under the supervision of an allergist (the theory being that antigens stay in the system 5 days). Supervision really just meant that he suggested I do it and wanted to know if I did and to let him know if there were problems. My allergies improved both times, but didn’t vanish. I found the first day on the water fast was a little uncomfortable, days 2 and 3 were easy, and by day 4 I was feeling a little faint. I think a water fast was actually easier than a severely calorie restricted diet, because I didn’t have to make any choices.
    I also once did 40 days of eating just supper – a mostly balanced meal but whatever I wanted to – which ended up being about 1000-1200 calories. I have no idea what health benefits it brought me, but I did lose the last 12 pounds I wanted to lose at that time. Again, it was easier because I was limiting choice.
    A couple of years ago (at age 66) I told my doctor I wouldn’t take statins, and that I was confident I could bring my cholesterol down with diet, and would she give me a month. I ate limited but not low carbs, lots of vegetables, limited meat but more beans and nuts. I had lots of olive oil, at least 2 T a day, but I think more could have been better. The garden was in full swing and I had a large green salad every day with homemade olive oil based vinaigrette. I think an important part of what I did was to have for breakfast most mornings: an onion and about 5 ounces of button mushrooms sauteed in olive oil, with green beans or green peas, maybe a slice of bacon or 5-6 slices of pepperoni or an ounce of cheese. Sometimes a small potato nuked and sliced and sauteed along with the other vegetables. This really assuaged my hunger, as did eating less wheat. It had not been my goal initially to lose weight, but I found to my surprise that I lost 11 pounds over 5 weeks. My Total cholesterol went from 253 to 173. LDL 164 to 95. HDL 57 to 54. Triglycerides 158 to 119.
    After a bout with viral bronchitis and prednisone last year my A1C went to 6.7, and I realized I had to do something. It has come back down to 6.3, but this is still not good, and I want to get it lower.
    I’m trying to do a minimum 15-16hr fast overnight at least 5 days a week (5pm to 9am), as science daily has indicated that even that has benefits. I keep thinking I’m going back to my cholesterol lowering diet, but haven’t. And I’m contemplating a modified fast. I’m still a bit confused about what would be required to give the same benefit as a water fast, and whether the same results could be achieved with a 5-2 fasting diet. How much of the benefit from the FMD comes from the calorie restriction itself, and how much from the proportions of protein, fat, and carbs. Does anyone have a handle on this?
    Science Daily is another source for the FMD news Bill cited from the BBC above, and in it they cite an earlier article this week on the overall benefits of the diet:

  12. Hello and thanks for this great article.

    I am 4th day of the FMD, do you reckon this diet it will slow down my metabolism and I will gain. Weight faster than before once I start again eating as I was doing before?

    Is there a sort of transition diet to apply after the 5 days are completed?

    Thanks in advance .

    Renato C.


  13. With this FMD, are we mimicking how our hunter-gatherer ancestors survived? You wander the savannah till you find a field of ____, eat for several days and then fast until you find the next food source whether it is a field of ________ or an animal.

    • The paleo framework gets some things right, but misses other things. My theory is that we are adapted for two different modes: one is to reproduce copiously and die quickly; the other is to hang in there through the famine until it’s a better time to reproduce. We want to throw our metabolisms into the second mode, and we rely on experimental trials and biomarkers to tell us how best to do this.

  14. Hi Josh,

    Which way below is better and will give us more health benefits?
    way#1: fast 5 consecutive days per month
    way#2: fast 15 consecutive days every three months

    I have been experienced both ways and found way#2 (fast 15 days) is actually easier for me, since my most difficult fast days is from day 2 to day 4. After day 4, I actually feel like normal and no hungry at all.

    I also read from lot of websites which stated that fast 15 days or so can clean your interior, drop your blood pressure, and give you even more benefits than 5 days of fasts.

    On the other hand, way#1 has a lot of data/experiment support from Valter Longo.

    So I wondered: now that 5 consecutive days of fasts is good, will 15 consecutive days of fasts even better?

    Thanks and regards,


    • I think you’re right that there’s just not enough data to answer this question. Even if we did have data, it would only be for short-term effects, and we’d have to make educated guesses about life extension. And even if we had data on fasting and life span, I’m guessing there would be substantial individual variation, so we are left guessing what is best for our particular metabolisms.

  15. Hi Josh, I’ve seen theres an upcoming edition of “Crackomg the aging code” for summer. Does it contain some updated text, or is just the paperback format the difference?

  16. Hi Josh, great article and thanks for spreading this information…I learned so much. I am surprised though that you mention some of the companies that simply buy off the shelves products which even the original producer does not have any science nor claim to mimic fasting and they resell those to consumers based on fake claims. I have clicked on all the links that you have in the website and it seems to me that Prolon is the only product that is scientifically tested as fasting mimicking diet and is the real product that USC developed. Live Box, etc. are just unlawfully banking on the research done at University of California. The FDA should clean house in the consumer food sector. Thanks

    • I agree. All this research should be publicly funded, so that they don’t have to jack up the prices of food and drugs to support their research departments. And — more important — so that the research is done by people who have no financial interest in the outcome.

  17. Do you believe that the fasting guideline is mainly cumulative caloric or is there anything “magical” about this ratio (9% protein, 44%fat and 47% carbohydrates)? I eat a ketogenic diet and do not eat nearly that many carbohydrates currently. If I go by the general ratios for a Ketogenic diet of 20% protein, 60% fat and 20% carbohydrates that puts me at appx 36g/49g/35g at 725 calories. Depending on the quantity of protein eaten at a sitting some gets converted to sugar regardless. My worry is two fold. I really do not want to lose muscle mass (so much to lose) but I also want this to be something fruitful and in the spirit of the FMD. Just wondering about your thoughts

    • I think low protein is important for the effect of the diet, and low carb is probably important for keeping the hungries at bay. You are asking: can you lower carb content further and still get the benefit of the diet? It sounds like a viable idea to me. We have data on the standard FMD because Longo took the time and expense to verify that it works. It seems likely there are other configurations that would work equally well, though we don’t have the data to prove it.

      • I am a runner and staying in ketosis is pretty important. In ketosis, fat is the way to keep hungries at bay. Luckily our bodies are already adapted, high fat and should be minimal to no effort/effect. It would be pretty simple to test both scenarios. I would probably start with what I know (attempting to stay in ketosis with fasting that is in line with that) and eventually see the difference if transitioning the fast to closer to the prescribed formula.

          • I know that it will be completely anecdotal and more of an exercise than anything since I am not analyzing my blood and cannot draw any conclusions exactly. I am willing to try and see what falls out. I know that fasting can be done, if careful so I am not taking any unnecessary risks. If I have anything to report, I will do so. Thanks!

  18. So here’s a question I’m sure you have given some thought to but I’ve not seen addressed. If I am heading into the FMD and weigh 100 pounds, the meals (total calories) will have very different meaning/outcome than if I weigh 200 pounds. I don’t think this is considered in the ProLon packages (or at least I’ve not noticed any option for different participants’ weights). I would think that finessing the amounts/total calories for the meals could assist in a desired outcome.

    Have you, Josh or Enid, considered whether the meals outlined are targeting a certain weight range which could/should be tweaked higher or lower depending on one’s weight? (I weigh 165-170 generally, and I figure that may be within the “average” range for the meals’—both the ProLon and the sample meals you and Enid have supplied—calibration.)

    Thanks again for your generous contributions!

  19. People interested in fasting should definitely follow Dr. Fung’s blog (intensive dietary management) as he is the most prolific writer and practical implementer of fasting that I know of. Something that he constantly stresses is that the advantage of fasting and other diets that up-regulate fat burning (LCHF) is that they maintain or increase metabolic rate while moderating irrational hunger, and eating the amount included in the FMD sound to me to be dangerously close to what would eliminate these benefits. His experience is that one should work up to fasting with nothing more than water/coffee/tea/bone broth and that small meals are only a stop-gap measure unless one has developed their “fasting muscle”.
    A few observations from my own experience:
    – I think (and Dr. Fung seems to confirm) that extended fasting for an overweight/diabetic person is going to be a much easier and net beneficial experience than for a lean healthy person.
    – I have very good benefits from a leangains/perfecthealthdiet- style 16/8 eating style, however…
    – I have not been able to go much longer than 16 hours without it negatively affecting my weightlifting. Fasting is supposed to be “muscle-sparing” but it seem to have some negative issue such as possibly shutting off strength growth (which would make sense) at least for me
    – If one really needs to fast for some therapeutic reason, it seems to be easy enough that there is no reason for mimicking it, just do it.

    • Thx, Drifter. I have built-up from one day fasts to my first 3 day fast. I will be finishing this 3 day fast tomorrow morning. What is recommended after the fast? I am on the keto diet and, since I have experienced no side effects from fasting, I am inclined to just resuming my “regular” eating regimen. On the web, I have found recommendations for drinking juices only for… However, juice would be outside of the keto regimen I am enjoying.

      As an aside, fasting, so far, has been an exhilarating experience for me. I plan to go to the site you suggest.

  20. Hey Josh
    Is there a way to mimic the Fasting Mimicking Diet with grab and go foods from the grocery store? Where the only food prep might be adding hot water or microwaving a soup? For those of us who travel? Thanks so much for all your research and info!

    • Hi Kathy,

      I haven’t checked the math in detail, but this looks plausible, and it seems like it might be close enough to be effective (e.g., especially not going over on protein): Eat only avocado for the whole week.

      Day 1: 3 avocados
      Days 2–5: 2 avocados (taking size into account!)

      Avocado = 160 kcal/g, so
      681 g on the first day,
      453g on the remaining days.

      Not super appealing, but the simplest approximation that I’ve seen. He also takes some veggie powder for micronutrients. Enjoy 🙂

    • hi Kathy,

      I’m on day 5 of the lifebox FMD and their foods are all off the shelf. Packet plain instant oatmeal with small tube almond butter for b’fast, kind bar + small packet nuts for lunch and vana brand legume bowl (pretty good really) or quinoa bowl for dinner.

      They also include gynostemma AKA Jiaogulan teabags and packets of coffee with chaga and some other herb.

      Surprisingly easy 5 days.

        • Hi Kathy,

          Yes, I bought it from online site. They are the 2nd online site selling a FMD in a kit. Prolon is the other one but I hate olives which are in prolon’s kit.

          Lifebox’s kit is $119 + shipping, and has the above as days 2-5 with day 1 being different and like 1000 cal vs 700 above for days 2-5. I just finished my 5 days and have lost 7 lbs.

          You could certainly assemble the stuff yourself but it is simpler just buying it. Also you get a 30 min phone consultation basically just talked about pitfalls and mistakes, how to resume eating afterwards, etc.

          • Kathy,

            PS I just ran across the fact that intermittent fasting does not work the same for women, and that women’s bodies don’t react the same way as men’s to fasting in general. So you might want to do some research before trying this out.

          • Scott,
            do you know if the macronutrient content is the same as the ProLon diet?
            PS Thanks for the info!

  21. Howdy Josh, I benefitted hugely from your writing about the Fasting Mimicking Diet along with that by Quantified Bob and Damien at Quantified Body. Thank you 🙂

    I recently ran my first cycle and have prepared a guide for others wishing to do so which would be especially helpful for UK based folks as it includes specification of all the food eaten and biomarker tests.

    Guide on How perform a Fasting Mimicking Diet cycle

    My personal results, learning points & next steps –

    Within the Guide I have also made available a Google Sheets template to aid preparation, planning and tracking. Hope it helps 🙂

    My results were . . . . *mixed* and *curious*. I will be running further cycles and refining both my approach to the FMD itself and the measurement.

  22. Thanks Josh again for all your work on this. Also thanks Ben for sharing your personal results I have tried a few cycles of FMD and always lost weight and felt better afterwards. Recently I have noticed that my body temperature has fallen by about 2 degrees below normal and weight loss has been more difficult. I am hoping that more regular FMD will address this. Would appreciate any thoughts or experiences anyone has had with this drop in temperature

  23. What I dont understand is the one size fits all. A six foot tall male and a 4’7″ female would have considerable differences in caloric intake to maintain an equivalent BMI. it makes no sense to provide them both with the same calories. The tiny woman may not be restricted nearly enough and a really large muscular guy maybe too much. Shouldnt this be factored into the diet?

  24. An alternative approach to FMD is the ketogenic diet – targeting similar biochemistry by reducing carbohydrate to low levels and using the body’s natural ability to burn fats for fuel. It’s an every day diet, has proven results against obesity, pre-diabetic conditions and Type 2 diabetes. Recent research is showing promising evidence of neurological benefits – it’s long been used against epilepsy / seizures, but is now being investigated for effects mitigating Alzheimer’s and Parkinson’s. It also appears that keto dieters experience natural body adaptation effects tied in to our evolution, with the result that for many it “feels right” and becomes a successful long term strategy for health improvement, improved physique (increases in lean body mass) and performance. It’s being taken up by high level athletes from the Tour de France to many ultra endurance running events, soccer, rugby and tennis.

    There are also longevity enhancing aspects to the biochemical changes that occur on the diet, also subject to current research.

    Drs / Professors Phinney and Volek have done the most concentrated work and have several talks on the tube and they are backed up by a great deal of quality research.

  25. I have been Inintermittent fasting for the past 7 months. I try to get at least 16 hours of fasting per day, at least 5 days per week. I never go more than 24 hours. Here has been my experience FWIW:

    -Insulin went from 19 all the way down to 5.6
    -fasting glucose went from 104 down to 92
    -lost 18 lbs (I’m 5’5, 156lbs.)
    -every one of my cholesterol numbers have improved dramatically
    -C- Reatcive protein went under 1

    I just started the L-Nutra FMD yesterday. I’ll report back after a couple cycles of that.


  26. Hi Josh,
    Thanks for the great work. My interest began when I learned of Dr. Longo’s work with mice with EAE (M.S). Most notable to me was complete reversal of symptoms in 20+% of the animals that did the FMD, and improvements in essentially all the animals. These results are better than the clinical outcomes of all major M.S. drugs,
    and I have tried them all, and with the possible exemption of one course of Tysabri, I am experiencing better results, typically gradually during “refeeding”, which is 5 days after the 5 day FMD. I was diagnosed with MS 28 years ago and have very limited mobility. I have tried a “Prolon mimicking diet”(thats a joke but the manufacturer, Lifebox, is essentially providing just that. My 4th and 5th F.M.D. I have eaten 10% protein, 65% fat and 25% carbs (roughly 50 grams) using my own food choices as it is pretty clear low protein is the key variable in the “macros” of the FMD( if you are interested in making your own food choices, you might use, which I find helpful in planning my diet, which is predominately macadamia nuts or peanut butter as the bulk of my calories and fat, and vegetables the same for carbs. I eat less fruit than Longo would allow as I try to keep carbs to 50g/day to deepen the state of ketosis.
    I am on day 4 of my 5th FMD today. I have done these in a little over a year, though I discontinued my 2nd and 3 FMD, primarily due to exhaustion. What is most exciting to me is some clear improvement in my mobility after “refeeding” after the 1st and 4th
    FMD’s, not to mention enhanced mood and 4-5lb weight loss (per completed fast), which is a nice “side effect”. A few things I wanted to share in my experience-1-my hunger dissipates dramatically by the end of day 2-today, day 4, it was all but non-existent)
    2-I believe, though I’ve never tried a long water fast, the FMD diet is substantially easier for me than a “water only fast” would be,as the ability to eat modestly makes a large difference, as well as likely healthier.
    3-I think for people with weakened autoimmune systems, trying the FMD is a “no brainer”, though for those with “normal” immune systems It is likely of less benefit. Dr. Longo has done some very promising work that shows a marked reduction in cancer risk.

  27. I have done my own FMD three times and each time I notice real benefit. During my first FMD, I pushed my Fibromyalgia into remission (I had FM for 7 years). The second FMD my eczema vanished. I lost 4-5 lbs during each FMD and it seems to trigger my body to continue to loose weight. It is great for my skin, too..makes it so soft. I will be comparing my blood work soon with pre-FMD levels. I am trying to lower glucose, cholesterol and liver enzymes.

    • Maureen, how are you eating between FMD cycles? I’m on day 4 of the ProLon FMD and trying to decide whether to go back into plant-based keto or try to follow Dr. Longo’s recommendation of a low-protein plant-based Mediterranean diet. Either way, I’m planning to keep my protein down based on Dr. Longo’s research, plus I’m mostly vegan so it’s easier that way. Also, are you doing a homemade FMD or some other version? Do you mind sharing some details of your FMD? Thanks!

  28. I’m curiousHello,

    I’m curious whether there are good reasons for the ratio of carbs in the CR plan. In other words, will the results be similar if the overall calorie counts (and micronutrients) for the five days remain the same as the FMD protocol, but with a more keto-friendly balance?

  29. I did 3 session of FMD over 4 months and I found it easy once you start. I do running to keep fit and I notice about about 3 weeks later quite an increase in lung capacity and also feeling quite stronger. I formulated my own diet from Cronometer because the L Nutra cost is ridiculously high if you are someone of moderate means. The third time I felt so great that I done it for one week instead of five days. I think it is important not to do it to often because it may leave one malnourished and cause problems undocumented.

    I also have just done the FMD and ended today. The set of 3 I finished 4 months ago. Personally I believe that intermittent 8/16 fasting is the easiest and it does not upset one’s life rhythm. An other alternative occasionally diet restricting for a couple of days every few weeks which is easy if you find it easy to control the habit of eating

  30. I have a serious autoimmune disease that did not respond to the prescribed medication. I read Longo’s study wherein he noted the killing off of autoimmune T cells and regeneration of T cells and stem cells, when rodents were put on the FMD for 5 consecutive days.
    I thus started a 5 days water fast – and pain and symptoms decreased significantly. Two weeks later I did another 5 days water fast – symptoms decreased even further. But it became mentally taxing. Fasting for 5 days on top of a disease that is influencing my mood, made me really quite depressed. Certainly since I felt I ‘had’ to do these water fasts, or face serious health consequences as my symptoms indicated. It felt stressful and depressing.

    I decided to buy the FMD. But it’s very expensive for me, given all the healthcare costs I’m running into. My results were a bit less evident than on a 5 days water fast, but I certainly noticed a decrease in symptoms nonetheless. (I do reach a much deeper state of ketosis on a water fast). (In addition I eat the diet Longo recommends in his book in between my FMD’s). However, 3-4 weeks after the FMD my disease symptoms are again very much present, and very disconcerting again. This makes me think doing the FMD twice per month for now, would be more helpful for me, to push back autoimmune symptoms.

    I read your FMD-recipes and it sounds like a fantastic idea. Thanks for posting them. I hope I can ask though: do you really think this is quite similar to the FMD? I assume these recipes were based on the patent. ProLon states their diet is made in such ways that it prevents cell growth. And it seems they indicate this is not only since the diet contains a certain ratio of carbs/fats/proteins but also because of specific nutrients and vitamins that were added to the diet. Glycerol is also a part of the FMD.
    I would gladly try a homemade FMD, since the Prolon-diet has some ingredients I prefer not to take (a little bit of cane sugar amongst it, ‘natural flavors’, honey, and most ingredients don’t seem to be organic). And it is very expensive. But I would want to be sure I could achieve the same thing as with the Prolon-diet on a homemade FMD – certainly given the severity of my disease (symptoms). As such I have been a bit cautious thus far to try a homemade FMD instead. Albeit from a cost/ingredient perspective I would certainly prefer to.
    Many thanks for any input.

  31. You point about our disfunctional health system is a key reason we have all to rely on either anecdotal comments with no scientific basis or unqualified people with blogs making things up out of whole cloth. Regarding a paleo diet, our ancestors relied a good deal on gathered items from plants. Meat was also consumed but not to the exclusion of high fiber plant foods. We really have no idea what their diet consisted of. However, this much is certain: they were MUCH more physically active.

    With a health system whose purpose is to improve our well-being and increase our longevity, we would be doing research aimed at gathering information on a much larger scale than we do today. The food and drug industries, big ag and big pharma, along with the medical industrial complex, wants us to be subpar in order to sell us stuff whether or not it works and whether or not it is harmful, nevermind beneficial. We are just hamburgers served at the plutocrat barbecue. If people reading your blog would vote in their own self interest, we could change things quickly. But we are a flawed species and vote our religion and our racial biases and so we will remain in the dark.

Leave a Reply

Your email address will not be published. Required fields are marked *