Real Life Extension: Caloric Restriction or Intermittent Fasting? (Part 2)

There are options for extending your life, but is it worth it? (Photo: Megan*)

This is the second half of our two-part article on real experiments (and successes) in life extension, authored by Dr. Michael Eades. Part 1 covers supporting research for caloric extension (CR) and intermittent fasting (IF).

Dr. Eades continued from Part 1:

We fooled around with a number of different eat-fast-eat regimens and came up with something that works pretty well. We set up our cutoff time as 6 PM. On the day we started, we ate until 6 PM, then fasted until 6 PM the next day. On the next day we ate supper right after 6 PM and ate breakfast and lunch (and a few snacks) the next day until 6 PM when we started fasting again.

The advantage of this regimen is that we were able to eat every day. One day we would get supper–the next day we would get breakfast and lunch. On no days would we go entirely without food. This schedule worked the best for us.

The big surprise in the whole process was how easy the whole thing was. We realized that intermittent fasting and dieting had opposing attributes and disadvantages. Diets are easy in the contemplation, difficult in the execution. IF is just the opposite – it’s difficult in the contemplation but easy in the execution. Here’s what I mean.

Most of us have contemplated going on a diet. When we find a diet that appeals to us, it seems as if it will be a breeze to do. But when we get into the nitty gritty of it, it becomes tough. For example, I stay on a low-carb diet almost all the time. But if I think about going on a low-fat diet, it looks easy. I think about bagels, whole wheat bread and jelly, mashed potatoes, corn, bananas by the dozen, etc. – all of which sound appealing. But were I to embark on such a low-fat diet I would soon tire of it and wish I could have meat and eggs. So a diet is easy in contemplation, but not so easy in the long-term execution.

Intermittent fasting is hard in the contemplation, of that there is no doubt. “You go without food for 24 hours?” people would ask, incredulously when we explained what we were doing. “I could never do that.” But once started, it’s a snap. No worries about what and where to eat for one or two out of the three meals per day. It’s a great liberation. Your food expenditures plummet. And you’re not particularly hungry. You’re either eating until 6 PM or you’ve got a meal waiting at 6 PM, so though it’s tough to overcome the idea of going without food, once you begin the regimen, nothing could be easier.

My wife and I fooled around with our regimen for a few weeks here and there just to prove to ourselves that we could live with it and that it was a doable strategy for just about anyone. We ultimately drifted back to our normal low-carb existence just because it seemed to work better with our schedules. It seemed that we always ended up with some kind of dinner engagement on the nights we were supposed to be fasting, necessitating a change in our fasting schedule.

Over the period that we followed the various IF regimens we lost a couple of pounds (we really didn’t have much weight to lose, nor did we have health problems that needed fixing) because, unlike the rodents, we couldn’t eat twice as much during the eating days as we would have eaten were we not fasting. We didn’t check any lab work to see if any values had changed. We weren’t doing a hard-core study; we were simply evaluating IF as a practical means for humans to use to improve their health.

I then wrote a blog post about IF that became the most commented post on my blog. It seems that the idea of IF had struck a chord with a lot of people, many of whom took up the torch and started IFing.

People started commenting that they were doing great on the IF. Some were losing weight, but others weren’t. Or if they were, they were losing much less than they thought they should be losing given the caloric reduction. As I mentioned, it seems that humans have a difficult time doubling up on calories on eat days, so in most humans an IF is also a reduced-calorie diet. And humans, it appeared, weren’t losing as much as their reduction in calories would predict. Reports started popping up on low-carb bulletin boards describing how blood sugar levels had gone up in people IFing and how some people had seen their blood pressure go up.

Like many of my readers, the research community had jumped on the IF bandwagon as well. And, in a similar fashion, the results were not all positive. Papers appeared showing that subjects IFing, or even regularly skipping a couple of meals per day, were developing insulin resistance, impaired glucose tolerance, elevated blood pressure, and decreased thermogenesis. Even Mark Mattson published a couple of human studies, including a randomized crossover designed experiment that showing the above disorders in women who ate the same number of calories in one meal per day as opposed to three meals per day.

I must hasten to add that the loss of insulin sensitivity, the impaired glucose tolerance and high blood pressure did not reach major levels. But they were significantly more pronounced than the same measures in the same subjects consuming the same number of calories divided into three meals instead of just one. The finding that troubles me the most, however, is the decrease in thermogenesis found under iso-caloric conditions. Said decrease in thermogenesis can only be worse in a true, real-world, intermittent fast in which the calories are typically lower than usual.

The decreased thermogenesis explains why the IF doesn’t work particularly well as a weight-loss regimen even though in most cases it is a reduced calorie diet [see the “the real science of fat-loss: why a calorie isn’t always a calorie” post for more on this phenomenon]. The subjects in these studies who consumed only one meal per day had reduced thermogenesis even while consuming the same number of calories that they did when eating three times per day. Imagine the reduction in thermogenesis if the calories were reduced as well as they are in most IF regimens.

The energy balance equation states that the change in weight equals calories in minus calories out.

Δ Wt = kcal in – kcal out

Many people think that the items on the right side of that equation are independent variables. In other words, if kcal in decreases weight will be lost because kcal out stays the same. But it doesn’t work that way because those terms aren’t independent variables – they are dependent variables. If kcal in goes down, often kcal out goes down as well to compensate. If people increase kcal out by exercising, they end up increasing kcal in because they eat more. It’s called working up an appetite. And since exercise doesn’t burn a whole lot more calories than simply sitting on one’s butt, it doesn’t take a lot of food to compensate. This effect is called adaptive thermogenesis. (Here is a full text article that goes into depth regarding the mechanisms involved.)

IF fasting, by significantly decreasing thermogenesis, decreases kcal out because our thermogenesis is what burns a whole lot of our calories. If the kcal in are decreased by the IF and the kcal out are decreased by the diminished thermogenesis brought about by the IF, it’s no wonder the IF doesn’t result in a lot of weight loss for most people.

The one question that remains unanswered is whether or not the intermittent fast followed in a low-carbohydrate way will lead to these same problems. To me, that point is kind of moot. Why? Because I looked at the IF as a strategy that allowed me to eat a lot of high carb foods that I would normally avoid and not pay the health consequences for it. If I’m going to limit myself to low-carb foods, why go on the IF? I can get the same results just following a regular, whole-food, low-carb diet without having to eat only every other day.

It’s looking like the intermittent fast is another of those ideas in science that looks good in animal studies then not so good in human studies, proving once again that rats and mice aren’t simply furry little humans. And it appears – for humans, at least – that the intermittent fast is indeed beginning to look like the reality of a late-night gimmicky infomercial: long on promises, short on delivery. I suspect that it is also a cautionary tale about the applicability of caloric restriction studies to humans.

Sorry to be the bearer of bad news, but that’s the way science sometimes works. Lab results and reality are often two different animals.

Guest writer biography: Dr. Michael Eades is one of the best-known bariatric (obesity treatment) doctors in the US and was the first doctor to introduce insulin resistance to the mainstream via his books, including the national best seller Protein Power.

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115 Replies to “Real Life Extension: Caloric Restriction or Intermittent Fasting? (Part 2)”

    1. Probably, that is part of a reason that citing them so often as a source of knowledge of how we “ought” to live/eat/etc, does not make that much sense to me.

      1. Well, yes and no. Understand that ‘lifespan’ as a metric averages how long each infant born to a particular population can expect to live. In other words, societies with high infant mortality rates can expect their ‘lifespans’ to come down quite a bit. Paleolithic man could easily live into his 60s, 70s, or even 80s, much like modern man can. But without prenatal care, hospitals, sterile delivery rooms, antibiotics, and starvation, infants were MUCH less likely to make it to toddler age.

      2. Most humans died of early age due to problems with their teeth/mouth. Along with the reasons said above, I doubt anyone lived those high of years.

  1. Aloha!

    Kudos on EVERYTHING. My wife Anna and I have been living what we affectionately call “The National Geographic Lifestyle” for some time now, living in amazing places (Texas’ Big Bend region, Hawai’i), meeting amazing people (!!) and doing amazing things (!!!). We’re in the Puna district of the Big Island now, using T4HW as an instruction manual for a lifestyle we’ve been refining for years.

    You’ve nailed it, man. Maybe we’ll cross paths along the way.




    Hi Dave,

    Congrats on all, and thanks for the kind words! As for the offending content, I’m not sure what you’re referring to, but thanks all the same, I suppose 🙂 Perhaps that was in response to another commenter…

    All the best,


    PS – We’ve removed the offending content from our website. Google had it flagged.

  2. I still believe there are just too many variables to an IF implementation to dismiss it. Such as could the person IF daily with shorter eating window? Could the person start 1x a week? How many meals does the person have in the eating window? Is the person eating healthy? Is the person eating junk food? Does the person exercise? Is it strength training? How often does one IF per week? Do you take weekeneds off? etc…etc…etc.

    That being said, IF works for some….and may not work for others. But there are always variables to change around and play with. I believe fasting must be a part of a person’s lifestyle for maximum health. Otherwise if you are always busy eating (which sucks up alot of the body’s energy), it takes away from the functions of cleansing, repairing and rebuilding cells? Especially in those that may already be at greater risk, toxic overload or have more damage that needs to be repaired?

    Alot of people doing exercise (CF especially) have seen positive results with the daily fasting of 15-18hours and eating Paleo type foods otherwise. There can also be advantages to that protocol M-F with the weekends off to enjoy more choices. Carb cycling can also be applied to the pwo workout window and/or high/low days.

    In the end. IF can work for weight loss if you are not eating crap and exercising. Eating healthy all day of course can also work for losing weight. IF gives other benefits to promoting life and disease prevention other than weight loss that something such as CR (calorie restriction) does not. One must modify IF to their lifestyle and goals. I just love not stressing about food all day long (but I also know how to eat healthy).

    Brain – Paleo man’s lifestyle was not based on cancer or heart disease. It was more because he got eaten by a tiger, broke his leg and starved to death, or some other thing that would be fixed by emergency care today or a quick trip to the supermarket. Had little to do with his long term health parameters.

    1. I totally agree with this comment from Mike OD.

      Dr Eades even admits “I looked at the IF as a strategy that allowed me to eat a lot of high carb foods that I would normally avoid and not pay the health consequences for it.”

      IF will help with weight loss for some people (those not chunking up on high calorie processed foods when not fasting) and for those for whom weight loss is not an issue there is plenty of evidence to suggest a whole host of other health benefits contributing towards longevity and well being.

      Other rarely mentioned benefits which I’ve personally gained from IF:

      I no longer fear hunger. Hunger pangs are over within 5 minutes and in a 24 hour fast, once adapted, will only occur 2-3 times. This means there are plenty of other times on non fast days when I don’t immediately gobble the closest and most available food as soon as I’m hungry (often very unhealthy food if out and about at the time) and instead often choose to wait until I can eat something healthy.

      Rather than fasting in order to then eat whatever I want the rest of the time, I found I made much healthier choices throughout the week.

      I also massively reduced my portion sizes when I was eating, completely subconsciously. I just found I couldn’t stomach as much food in one sitting. I actually felt full and when full, able to stop eating.

  3. It seems that you’ve contradicted yourself. You say in Part I that you think the paleolithic diet is optimum for modern man, but then in Part II here, you say that you looked at IF as a strategy for consuming high-carb foods without paying for it. I think that you’ve sabotaged your dieting results.

    The thermogenic effects of eating a Paleo/Low-carb diet combined with IF should be the way to do it… not intermittent fasting between high-carb days. Going with the Paleo analogy, Paleolithic man didn’t eat bread and potatoes in between fasts, he gorged on more protein and fat.

    Also, it seems to me that the best meal to have on your one-meal days would be the morning meal, no? Fast between 9:00am and 9:00am…

    The article is still an interesting read, though. Thanks!

  4. Hmm. Interesting that when ‘part I’ (the “yay, we’re going to try IF” portion) was published, it got 25 comments, many extolling the benefits of IF.

    When ‘part II,’ by the same author, noting newer research and issues with IF and the possibility that “it appears – for humans, at least – that the intermittent fast is indeed beginning to look like the reality of a late-night gimmicky infomercial: long on promises, short on delivery. I suspect that it is also a cautionary tale about the applicability of caloric restriction studies in humans.”, somehow, the comment section and the chorus in support of IF goes silent.


  5. I don’t know much about IF, but I have some experience with religious fasting (24-26 hour fasts for Yom Kippur in Judaism; and my friends do sunrise-to-sunset fasting for Ramadan).

    Like I said, I don’t know about the heath effects. What I *have* noticed, from numerous yearly 24-hour fasts (sundown to sundown) is that by around 11 am on the day of the fast (ie: about 17 hours in), I get *extremely* hungry. At around 2 pm, the hunger goes away, but I become utterly incapable of any sustained mental focus. I can’t study, read novels, or do any of the other things that usually occupy my time.

    I can’t imagine doing this every other day. My productivity would plummet.

    Then again, I suppose other peoples’ mileage may vary. If it works for you, more power to you.

  6. On the contrary the Paleolithic man lived quite long. Take the Hunza Indians for example who lived over 100 and were reported to have erectile function @ 99. These beings lived without “modern society” and lived the “paleolithic” lifestyle. Much more on this topic can be read through the works of Westin A. Price in his book Nutrition and Physical Degeneration.

    Mr. Organic

  7. There’s a couple flaws in many of the animal studies. Rats generally are fed the same thing regardless of caloric intake. Humans, however, tend to eat poorer as calories go up. When we binge it’s usually pizza rather than grilled chicken.

    The other flaw is that most animals (and to some degree humans) are designed to eat all they can while food is available as they must prepare for times of famine. So the control group ends up eating way above maintenance calories. The reduced calorie group doesn’t get orca fat and therefore doesn’t get heart disease. Voila 20% longer lifespan.

    This doesn’t necessarily imply that an arbitrarily reduced calorie diet or periodic fasting is superior to eating a clean diet at maintenance calories (whole foods, higher protein, and less simple carbs).

  8. Hey Tim, what are you on Bryers-Miggs? There are tests online if you don’t know offhand.

    Curious if you are what I think you are (which I will encode below). The relevant question is whether your suggestions apply to all personality types, or whether you should, in the interest of correctness, claim a limited audience for your ideas.

    My guess for you (letters are shift twice right across keyboard such that an ‘A’ becomes a ‘D’). I encode it so that you can look at this AFTER testing yourself.


  9. Tim,

    I’m not trying to be overly critical, but I’m somewhat disappointed with this article. Part 1 was an exciting read, as IF seems to be a great discovery in life extension that many of us aren’t particularly aware of. Then I read Part 2, which discredits most of the supposed benefits of IF, and I wonder why you posted the article in the first place. I guess my question is, what was the purpose of this post?


  10. I agree. I was really excited about the implications made in the first post, and I consider you a reliable source Tim, so I trusted you. But this posting seems like a flipflop, and misplacing my trust always pisses me off.

    In future articles, will you say one thing, and then turn around and say another a few days later? Or is this a one-time deal?

  11. Tim,

    As I mentioned in a previous post, I’ve used variations of IF’ing, usually in the form of a 16/8 fasting/eating window. From the research I’ve found, it might increase insulin sensitivity for more favorable nutrient partitioning.

    IF’ing using a conjugated calorie scheme i.e. high carb, low fat on training days and low carb/higher fat/lower calories on non-training days, *should* keep insulin sensitivity high and maximize protein synthesis post workout (and new research showing an earlier protein synthesis peak in trained individuals).

    Assuming one hasn’t had psychological food issues in the past, this could be an effective tool in the trainee’s arsenal.



  12. Well, the humans didn’t do the study correctly so the data there seems pretty useless. Also, food quality is an issue. I’m not saying this to support IF but just to say the data looks shaky.

    By the way, the statement about exercising not burning many calories only applies if the exercise you’re doing isn’t building muscle. Something like unchallenging aerobic activity which many people think will help them lose weight and discover otherwise.

  13. The purpose of this post is just this: other peoples thoughts and opinions are just that. Also you should never be satisfied with what you know or have been initially told.

    Part one of the article was an introduction and brief reflection on a subject which may be new to many readers. Part two actually describes scientific data and results. All I’m saying about the information in part one is that you mustn’t read it like scripture. To support my second point I’d like to add that not even all the data from the studies were identical.

    So after reading both of these posts the reader will have a decent introduction and a basic understanding of the subject. Yet you shouldn’t feel as though that is all there is to know on the subject.

    One more thing; I agree with Allen about simply eating a clean healthy diet. I don’t know why things ever really have to be more complicated than that. Refer to Tim’s post here:How to Lose 20 lbs. of Fat in 30 Days… Without Doing Any Exercise.

  14. I’ll follow a Paleolithic diet as soon as I’m living a Paleolithic lifestyle. Until then it’s nonsense.

  15. The only problems with diets like these is that they aren’t worth it. Severely cutting down on food fed to worms lengthens their life as well. It is a proven theory. The problem with not eating is that the quality of life becomes so low that those years aren’t worth living.

    Like the old joke: A guy walks into the doctor’s office. After being examined, the doc says, “I am sorry but you only have 3 months to live.”

    The guys asks if there is anything he can do to live longer.

    The doc replies, “You can quit drinking, smoking, and womanizing.”

    “Really? and that will help me live longer?” he eagerly replies

    “No, but you will sure feel like it.”

  16. So it looks like you’re saying IF is good for health/longevity/reducing appetite? But bad for weightloss?

    If so I should definitely give it a try. (always hungry and can’t gain a pound to save my life)

  17. I’m curious. If you’re on a fasting day, how is day to day activity? Can you do more, or are you restricted by lack of food. I believe I read in the previous one that the test mice just laid around.

    If this extends your life, but you end up spending every other day just laying around, than what’s the point?

    1. I do 2 hour hardcore workouts on my fast days (as well as non-fast days) and most of the time feel more energised on fast days but certainly never feel noticeably less energised. On the first 3-4 fasts some people may feel ropey/grumpy/lethargic but I suggest this is probably psychological and not physiological. After your body (and mind) adapt to them the anecdotal evidence leans far more towards feeling more alert and energised on fast days, not lethargic.

  18. I think the big key here is connecting IF with exercise. If you are sedentary and you skip meals, then yes, you may have some problems. But if you are active, then fasting naturally fits into the cycle.

    For example, let’s say you exercise and work up an appetite. Then you feast. After this, you could then fast, as would have happened in caveman days.

    Exercise-Feast-Fast. And then repeat.

  19. The Mattson IF studies referenced here were not lowcarb/paleo diets. In fact, it seems the subjects ate about 300g/day of high-glycemic carbs. So yeah, it’s better to spread the sugar out over the day than hit your body all at once…I’ve yet to see a relevant study done on humans.

  20. One thing that one might get out of all this is to use caution when theorizing about evolution. In my opinion, lots of this theorizing, including theories about the “paleo diet”, is merely the telling of “just so” stories about evolution. The recent research announcement that evolution currently proceeds at a rate up to 100 times faster than it did many thousands of years ago should make one cautious about saying that “evolution” has made humans adapted to a certain way of life, such as a certain diet or, in this case, a certain eating schedule. We can make informed guesses, but the fact is that we really don’t know.

  21. While some readers may be disappointed by this second post – I’m relieved. Your breakfast for the past 4 days (and counting) depletes most of my available self-discipline.. I’m not sure I could add fasting to that.

    There’s nothing like a little salsa and spinach at 7.30am. 🙂

  22. @Dustin Lemos,

    Some people thrive on gimmicks and rhetoric. Others prefer sincerity and results. It is my belief that the latter are the ones who get places in life, while the former are more likely to get stuck on treadmills.

    I think the 4HWW philosophy represents the non-gimmicky, results-driven side (despite some of its negative reputation). As far as I’m concerned, this was a wonderful post because it rang with sincerity, even though the truth wasn’t as sensational as we might have hoped.

  23. I’m glad you posted both points of view of this lifestyle. I think this fasting thing would make it very easy for someone with say, a food addiction or an eating disorder to run with the ball and perhaps get into some very dangerous territory health-wise.

    That said, people on the other extreme, who eat a fairly crap diet could probably see great benefits in simply being educated on “what’s good to eat,” not to mention the immense benefit of EXERCISE!

    Maybe moderation and balance wouldn’t allow them to become rail-thin, but incresed vitality isn’t all about starving or feasting, it’s about balance. Feeling good, instead of “sated” or “deprived.” Having a healthy relationship with food instead of an antagonistic relationship with one of the great pleasures of life: EATING!!

  24. Hmmmmm, I can’t see the full text of the Mattson crossover study, and the abstract doesn’t seem to give the macronutrient composition for the study diet(s). But if there was significant carbohydrate in the diets, it may not be particularly surprising that eating 1-2 days worth of carbohydrates (probably 300-600g) in one sitting would increase insulin resistance.

  25. Like others, I struggle with the duality in this post. In Part I, both research and anecdotal/theory is cited to support IF. In Part II, it seems more anecdotal evidence is used — I’m not sure reports on bulletin boards make for a very scientific conclusion. As Mike rightfully pointed out, there are a ton of variables that all could work to obfuscate conclusions on IF. Can you really draw a conclusion on IF based on bulletin board reports mixed with an (albeit interesting) explanation on thermogenesis?

    I don’t think so.

    What particularly bothered me about this article, was this paragraph:

    The one question that remains unanswered is whether or not the intermittent fast followed in a low-carbohydrate way will lead to these same problems. To me, that point is kind of moot. Why? Because I looked at the IF as a strategy that allowed me to eat a lot of high carb foods that I would normally avoid and not pay the health consequences for it.

    First, that isn’t the one question that remains unanswered. Even assuming that the anecdotal, non-scientific bulletin board posts passed as evidence (which they do not, at least not by themselves), the question remains: would a paleolithic (low-carb) diet in conjunction with IF lead to improved health benefits? You implicitly acknowledge that you haven’t answered that question by suggesting that IF (for you) allowed you to eat a bunch of high carb foods.

    You go on to ask and answer:

    If I’m going to limit myself to low-carb foods, why go on the IF? I can get the same results just following a regular, whole-food, low-carb diet without having to eat only every other day.

    Here, you conclude (hastily, I believe) that you can get the same results by merely following “regular, whole-food, low-carb diet”. Where is the research and anecdotal evidence to back up this claim? I find it interesting that you answer this question in a different way in Part I:

    If you accept, as I do, that the Paleolithic diet is the optimal diet for modern man due to our evolved physiologies, then you should probably also buy into the idea that a meal timing schedule more like that of Paleolithic man would provide benefit as well.

    If you really want to conclude on IF as it pertains to the Paleolithic diet, you need to research IF under the low-carb paradigm. Otherwise, you’re doing your readers (And potentially yourself) a disservice.

    As a sidenote, hasn’t Art Devany been practicing somewhat randomized IF for quite some time as part of his evolutionary fitness regiment? And though this is only anecdotal, his vitals are quite excellent.

    1. “As a sidenote, hasn’t Art Devany been practicing somewhat randomized IF for quite some time as part of his evolutionary fitness regiment? And though this is only anecdotal, his vitals are quite excellent.”

      As are Brad Phillon’s (Eat Stop Eat) and Martin Berkhan’s (

  26. This IFer’s not going silent!

    I am a very IR Type II diabetic. I first got interested in IF upon reading that it seemed to improve insulin sensitivity and reduce inflammation.

    I’ve been doing IF about 5 days a week for 9 months now. I eat all my food for the day in about a 2 hour evening eating window.

    I’ve seen significant improvements in my BG. Spiking after meals was a big problem for me, the worse was after breakfast, which would often shoot up 50 or 60 points.

    Now that I don’t eat all day, my BG stays nice and low and flat all day. And since my glucose stores are very depleted by the time I do eat, I believe my muscles take it up better. I have very little spiking now after my one meal. Last night I was 101 right before eating, and 104 1 hour after I stopped eating. I was never able to achieve BG numbers as good as that through LC alone.

    When I began Low Carbing 18 months ago, I was a walking pharmacy on Actos, Glipizide, Lantus, and 1500 Metformin. (Along with Lisinopril and Lovastatin). My A1c was still 11. Now it’s 5.2 and I no longer have metabolic syndrome.

    Now I’m off all of that except 1000 metformin. I just went off the insulin 1 week ago.

    I added IF 9 months ago. LC alone took me a great distance, but I was still struggling to get the BG numbers as low as I wanted them. Adding IF to LC really has taken me the rest of the way in reversing my diabetes.

    I’ve lost 127 pounds. Adding IF to LC neither increased or decreased my rate of weight loss. But it has improved my relationship and control over food. I think it will be a very useful tool as I begin maintenance.

  27. The thing that strikes me most about this very interesting article is the danger inherent in jumping on every passing bandwagon. I think the best advice for any normal adult is what the medical profession have been telling us for decades, to the extent that we maybe don’t listen any more.

    As a layman my summary would be as follows:

    Eat three modest size meals a day, giving a calorie intake a little over 2000 (for a man, maybe less for a woman).

    Don’t eat between meals.

    Avoid highly refined foods like the plague.

    Drink little alcohol (none would be better).

    Take a moderate amount of excercise.

    If your lifestyle makes you stressed, deal with it. Change jobs, do whatever you have to.

    If you do these things you stand a better than even chance of leading a long and healthy life.

    Trouble is this is just so mundane and boring that most of us seem to have stopped listening!


    1. “Drink little alcohol (none would be better)”. Does the research say that? My understand of the evidence is that moderate drinkers live longer than teetotalers. (Heavy drinking is obviously injurious to health).

  28. PS I just posted as Tim F. My apologies if I inadvertently misled anyone. I am not Tim Ferris, I am Tim Farnham.

  29. I agree with Dustin Lemos. It’s unscientific to compare IF eating high-carb to regular meals eating low-carb. A valid scientific experiment is done by changing one variable and only one variable (if possible). The rat studies didn’t go and feed the IF rats totally different food. They were all fed the same food. Only the meal timing changed. That is a crucial factor. As other commenters have noted, you do not see added benefits from IF unless you continue to eat your normal diet. If you eat a totally different diet, then you are throwing in multiple confounding variables.

  30. IF can and does work…if you don’t eat crap…or as I call it IFOC (Intermittent Fasting on Crap). The so called Mattson study of a group eating a boat load once a day for 8 weeks, is not intermittent fasting in my book…that’s just dumb eating. (I wish I could only eat a whole pizza every night and look like a model)

    Like said above, IF works if you:

    – break it down into smaller meals

    – don’t overdue the carbs (high insulin response)

    – use it “intermittently”

    – don’t use it as a pass/excuse to eat anything you want

    (of course along with exercise is always recommended as resistance training only helps to improve insulin sensitivity)

    Of course the whole increased longevity, increased health parameters and not obsessing about food is one of the big reasons why I still do it.

  31. I’m struck by the Paleolithic diet hypothesis and IF.

    Paleolithic people were both hunters and gatherers. Gathering gives you a steady stream of low-calorie (but often nutrient-dense) vegetables, especially greens, and the occasional fruits and nuts. All day, every day (provided you live in a warm climate!).

    Hunting gives you occasional (once every few days? maybe once a week?) bursts of high-calorie (relative to greens) lean meat.

    So if you were following a Paleolithic diet, wouldn’t you fast from meat (and splurge on a big lean buffalo burger once or twice a week), but keep eating mass quantities of greens (and some other vegetables, fruits and nuts occasionally) throughout?

  32. Tim,

    I am having a very hard time with this post. Contrary to this suggestions in this post, there is a very large body of research showing that there is no significant effect of fasting on human metabolic rate.

    This is true in studies examining models of IF as well as acute fasts of up to 72 hours in length.

    The comments on insulin resistance are accurate. However it should be noted that this is a result of increased reliance on Free fatty acids as a metabolic substrate, is transient, and returns to normal once feeding recommences. And, other trials have noticed improved insulin sensitivity with IF protocols.

    As far as IF being to difficult to maintain, this may be true of traditional, day-on day-off scenarios. However, it is my opinion that if someone were to fast once or twice a week and combine this dietary protocol with resistance training and maintaining their normal eating patterns during the times they do eat, they would see a 20% reduction in caloric intake, without a reduction in metabolic rate or loss of lean mass.

    Fasting only once or twice a week has been found to be easy by a very large number of people, from many different walks of life, with many different weight loss goals.

    Lastly, not all proponents of IF are also proponents of the paleo argument. Some of us simply see it as an easy way of reducing caloric intake that is easier than prolonged dieting.

    I enjoy the majority of your work, and will point out that I do have a vested interest in IF as I authored a book on the topic, however I still find it necessary to challenge the last couple paragraphs in this blog regarding IF and thermogensis.

    Normally I wouldn’t post such a negative comment, and I admit that Dr. Eades is basing his argument on scientific data but in my personal opinion, this post could easily be misinterpreted to be very close to the “starvation mode” scaremongering that occurs all to often in the diet industry.

    I am positive you could find a very large group of people who have seen impressive weight loss while following some form of an IF protocol. Just as you could find people who have lost an impressive amount of weight following a low-carb higher protein diet, or a simple calorie reduced diet such as weight watchers.

    In the end, its all about finding the easiest way to fit a caloric reduction into your lifestyle (whether this is a form of If, avoiding carbs, or counting ‘points’), and ignoring all the confusing rhetoric that is so prominent in this industry.

    Thanks for your time,


  33. A couple points:

    1. Eating/Nourishment is basic. We shouldn’t need to have to listen to a PhD to feel like we should be convinced about something. Micheal Pollan is a food expert and his advice is don’t listen to the experts, listen to your grandmother.

    2. Good presentation of science isn’t like a magic trick where you pull a bunny out of the had at the end. Or a joke with a punchline. State your case (preferrably with an abstract/executive summary) and defend it. I’d say the mini-series adheres more to the former than the latter.

  34. I definitely agree with Sarah K’s post on this subject.

    I think the your description of paleolithic diet could be a bit off, her model sounds more accurate.

    My theory is that fasting prolongs life of laboratory animals and because lab animals are not fed what they would typically eat in the wild. When they fast their body begins to heal from all the poisons they’ve put into it over time allowing for greater net life expectancy.

    The same principle holds true for humans as well. Humans fill their bodies with processed refined junk, alcohol, animal flesh, and animal byproducts that degenerate our condition of health over time. When Humans refrain from consuming those things for an extended period the body begins to heal itself, until these poisons are reintroduced. It seems logical that this would produce a net gain in life expectancy. It also seems logical like not putting all of those poisons into your body to begin with would create an even greater gain in life expectancy.

    I recommend reading Dr. Douglas Graham

    His website is at

  35. I’ve been following an intermittent fasting routine for about 13 months now. I take two 24 hour periods off of eating each week (for example I stopped eating last night at 9pm and I will resume eating tonight at 9pm)

    I’ve also done many 36 hour fasts in there and a few 48 hour fasts (I’m currently in the middle of a 56 hour fast…26 hours and counting!, I did a 48 hour fast last week, hit two weight/cardio workouts during it and I was fine). I’ve maintained all my muscle mass and dropped about 20 pounds this way. I’m 205lbs 6 feet tall and it hasn’t affected my strength or my muscle size.

    I’ve also checked my blood sugar on my fasts and it never drops below 4mmol which is totally normal, even if I do a workout at the end of the 24 hour period my blood sugar is always fine.

    Unless a person has a blood sugar disorder most healthy humans can easily go 24-36 hours without any change in their blood sugar levels, including a few regular weigth/cardio workouts. The reaction people have to long periods without food might actually be some sort of food addiction withdrawal at the brain/nervous system level and not a blood sugar issue at all. A recent article in scientific american mind illustrated this quite nicely.

    For those of you who want a thorough explanation of how IF works with your body I recommend you read Brad Pilon’s book Eat Stop Eat at He has compiled all the most recent science on IF and put it in terms that anyone can understand.

    I did my graduate studies in nutrition and human biology and had the privilege of editing the book so I have first hand experience with all of the research as well. I think all of your questions will be answered with this book.


    1. You stopped eating at 9 and will resume at 9 tonight.. = 24hrs

      “I’m in the middle of a 56hr fast at the moment, 26 hrs in”…

      at least have some consistancy.

      I did like Brad’s book especially the updated edition

  36. I posted a version of this comment over at Dr. Eades’s blog:

    I started IF on December 31 last year after reading Brad Pilon’s e-book ‘Eat-Stop-Eat’. Pilon recommends two 23-hour fasts per week, from after-dinner one day to before-dinner the next, claiming that the benefits (lipolysis, growth hormone production, and so on) really begin to kick in around the 15-18 hour mark. He also recommends three resistance workouts a week, to prevent muscle tissue from being consumed for fuel during the fasts.

    At the outset, my weight was about 198 lb. at the time (I’m 6?1?), and all my blood indicators (cholesterol, triglycerides, blood sugar) were excellent, so I was hardly in terrible shape. I was eating a relatively low-fat diet, but not much processed food.

    Intermittent fasting was a revelation. First of all, I couldn’t believe how good I felt during the fast. From my early adulthood onwards, I’d had frequent low-blood sugar episodes (which had disappeared almost completely after I’d stopped eating large amounts of bread for breakfast), and I was wondering if I’d get the same symptoms on a fast: dizziness, headaches, cold sweat, inability to think clearly.

    Nope. Nothing at all. In fact, I felt more alert and energized than I had in a long time. I walk to work, and on the way home on my fasting days (after ~22 hours without food) I often felt like sprinting just to use up the energy I was feeling, something I’d never experienced before.

    I get hungry towards the end of my fasts, sure, but not for carbs, and not in that craving, need-to-eat-now way that I’d been used to feeling. (Though I have to admit that diet sodas and sugar-free gum make it a lot easier to get by. They fill my need for flavour of some kind while on a fast.)

    Another fascinating effect is that IF has transformed my appetite. Before, I’d eat homemade muesli for breakfast, crave carbohydrates around 10am, then around lunchtime again, and then have a fairly large serving of starches with dinner. Now, I take only fruit, vegetables, and mixed nuts to work, and often find myself leaving bread and pasta to the side of my plate at dinner. I am much more capable of distinguishing actual hunger signals from routine cravings than I was before IF, and the cravings themselves have actually gone down dramatically. (I still often crave sugar in the form of chocolate or ice cream after dinner, and allow myself that indulgence. And wine is always on the evening menu!)

    Since I had such a reduced desire for starches, I decided after about a month to go much more high-fat low-carb, and increase my fasting to 3x a week. This has also been a resounding success: I cannot remember when I felt so good and so alert, I am far less hungry than I used to be, and my much reduced food intake is made up of much more satisfying substances. I look forward to my M/W/F fasts, and love to break them with a good meal. (I believe that my success with the Eat-Stop-Eat method has been due to the fact that you eat dinner every day, whereas a 30-hour full-day fast would be much more difficult to pull off.)

    I have to say, though, that IF hasn’t been much for weight loss, although that wasn’t my primary goal: I’m down to ~193 lb. from 198, and seem to have stabilized there, despite my much lower energy intake. However, Some of this will be lean muscle, since I’ve been doing core workouts 3-4 times a week. I have lost a substantial amount of fat around my midsection, gone up a belt notch, and several pairs of my pants are now too large to fit comfortably.

    I am eagerly awaiting the results of my next blood tests, due in August. Since my cholesterol and TG levels were already in the “excellent” category (my HDL might have been borderline TOO low), it will be fascinating to see if my new fasting plus HF/LC diet has done me any harm.

    So, my IF results after two months are as follows: No desire to binge on carbs, NO LOW BLOOD SUGAR EPISODES, far fewer cravings for junk foods, an increased intake of healthy, satisfying foods, and a huge improvement in alertness, well-being and healthful feeling. Works for me!

  37. I have done intermittent fasting all my life -I m 27, woman- without knowing that i was doing something special- i just eat when i m hungry and when i m really busy at work (I also travel a lot ) i just forget to eat. I don t follow a pattern with my meals -there are days when I eat my first meal in the evening and days when i eat 3-4 consistent meals a day. I do eat a lot of carbs and often sweets. I m really skinny but my doctor says i m perfectly healthy, I have a lot of energy, don t catch colds and my weight is very stable -it s hard for me to lose or gain weight. So it seems intermittent fasting is my natural way of eating and it works for me.

  38. I’ve been IFing since right before the Xmas holidays and man did it make a difference. I had been doing resistance training since last May, but still eating poorly. I made slow gains, but when I added fasting the progress picked up tremendously and suddenly in a matter of a couple of months I’m about half way to where I need to be. I’ve gotten off a couple of medications, my BP has come way down, and most particularly, the fasting has radically altered my appetite and given me real high-resolution, i.e., I don’t seem to crave food when I’m not particularly hungry. And, a bit of hunger has actually become a pleasant feeling rather than a gnawing feeling.

    Anyway, here’s my progress in pictures:

    And here’s some of my posts specifically dealing with my fasting experience, in chronological order. As you might notice, it has been a bit of an evolution for me.

    And if you’re not inclined to wade through all that, and I wouldn’t blame you, what I basically do and how I approach it is to put myself into what I call an “evolutionary state of hunger.” So, basically, I’m fed until I decide to stop eating and then I go for periods of 24 on up to 36 hours before eating, but I always polish off my fast with a very intense full-body resistance workout at the gym. Curiously, even if I haven’t eaten a thing in 30 hours and have a pretty deep hunger, 10 minutes into the workout and my appetite is completely killed, and hunger does not return until about an hour or two after the workout.

    It’s pretty much working out to two fasts per week, 30 hours each. I have found that lunch to dinner next day is actually far easier than dinner to dinner. I think it’s because by bedtime you have skipped dinner and so are hungry and during sleep your body better prepares you for the hunger. I wake with no hunger at all, and it’s pretty easy to take until dinner the next day.

    …Also, the fist few fasts had me pigging out a bit after. Now I eat normal meals like I always do (low/no carb, pretty high animal fat, moderate protein) both before and after fasts. In other words, I don’t try to make up the calories, nor do I use IF as a means to eat poorly. Haven’t been to a fast food joint or ordered a pizza in months, and it’s not willpower. It’s just I honestly haven’t the slightest desire.

  39. What you describe as eat / fast / eat is not intermittent fasting. The key characteristic of intermittency is that it breaks the pattern: in contrast, a regime of three square meals every other day is just as much a fixed pattern as three square meals a day every day. The point of breaking the fixed pattern is that it exercises the adaptivity of human body systems in ways that a fixed pattern doesn’t. The hypothesis is that this reflects the way our ancient ancestors ate – food being available most days, but not guaranteed every day – and is therefore better suited to our metabolic make-up.

  40. The best mix I’ve found is to eat ONLY when there is a genuine feeling of hunger. I believe there is magic in this ‘hungry’ feeling, and I like to experience it at least once a day. Unfortunately, that is just too simple for a lot of folks…

  41. This message – if one exists – gets lost in the “eat-whatever hype” in the beginning as well as the science jargon.

    Point: Eat to keep insulin low, boost your “anti-aging” hormones and more…This works, and it’s a balance of eating healthy fat, protein and slow carbs…

    Eades appears to be touting “eat as many calories as you want – in protein…live forever.” Or I just got tired of reading it and skipped the best parts of his story….???

    Fact is, those who eat more calories in fat and protein are satisfied quicker and feel as though they don’t have to count calories…And by keeping insulin low, they don’t get hungry that fast…Eating frequency should be every 4-5 hours…Try it and see if it works for you…After all, no solid rules truly exist.

    To Eades: Simplify and Thrive

  42. I am pretty disgusted right now.

    First we have these quotes from 9/13 and 9/19/06 articles:

    9/13/06 Fast way to better health article:

    “If you buy into the idea that the Paleolithic diet is the optimal diet for us today because it is the diet we were molded by the forces of natural selection to perform best on, then you should probably also buy into the idea that a meal timing schedule more like that of Paleolithic mean would provide benefit as well.

    One of the things MD and I took away from our IF experience is the idea that we don’t have to eat three meals per day. We now often skip lunch and don’t seem any the worse for it. Sometimes we get up and get going with all our projects and don’t eat breakfast. We try to skip a meal here and there because figure it’s probably good for us. When you get used to it, you don’t really even think about it. And it’s good for you. Don’t take my word for it–look at the medical literature.”

    9/19/06 PP vs. IF article: “Now, based on the IF research data, MD and I are of the opinion that a Protein Power style diet interspersed with a little fasting is probably the optimal diet.”

    “There is probably no magic in the 24 hours [fasting]; who knows, maybe it’s 15 hours[fasting]. It just isn’t known at this point. I’m firmly convinced, however, that there is an advantage to going without food for periods here and there. I’m convinced for a couple of reasons. First, all the data on IF is pretty persuasive…”

    “In short, IF is just an adjunct to the Protein Power diet that makes it work better by making it even more like the Paleolithic diet we cut our collective teeth on.”

    Now, in this article we have:

    “he one question that remains unanswered is whether or not the intermittent fast followed in a low-carbohydrate way will lead to these same problems. To me, that point is kind of moot. Why? Because I looked at the IF as a strategy that allowed me to eat a lot of high carb foods that I would normally avoid and not pay the health consequences for it. If I’m going to limit myself to low-carb foods, why go on the IF? I can get the same results just following a regular, whole-food, low-carb diet without having to eat only every other day.”

    So which is it???

    I’m trying to decide if we’ve all been inadvertently misled, purposely duped or just old-fashioned back-peddling after sticking one’s foot in one’s mouth and speaking about something they just really shouldn’t have.

    I’d really like to know which one, too.

  43. I am on a 36 hour fast right now (well, 35 hour since I lose an hour in daylight savings).

    I generally subscribe to the Paleo diet theory and think it’s useful to examine things from that perspective (rather than laboratory science).

    However, I find it hard to beleive that our ancestors fasted, then gorged, then hunted, then gorged, then fasted.

    All evolutionary science and anthropology points to the fact that our ancestors weren’t imbeciles like fish wandering around in an aquarium, waiting for fish food to drop. I’d imagine the hunters of the pack (let’s rule out the gatherers for now) packed a “snack” of some sort when going out on the hunt, to sustain them (whether a small game or big game hunt).

    Our ancestors were smart, analytical, and able to prepare ahead for the future. They didn’t leave home without something to sustain them.

    I do think there were periods of time of extended fast, in times of famine, for sure.

  44. I have been doing calorie restriction now for 3 years. A few points that I thought I’d make

    1) The large majority of CRer are not anxious, and not depressed, but are very happy people. They also are NOT violent despite low cholesterol levels. I’m less aggressive now than I have ever been in my life.

    2) Decreased thermogenesis is a BENEFIT of calorie restriction. Yes, decreased body temperature is related to the increase in lifespan of the little rodents. There is also evidence in humans that lower body temperature results in longer life

    3) Artificially increasing body temperature in a CR rodent eliminates or decreases the anti-cancer benefits of calorie restriction. Lower body temperature is good… it is something one should go for if they are interested in less cancer and a longer life. In animals that were eating an ad lib diet but had their temperature reduced by 0.5 degrees C lived upto 20% longer without CR or IF.


  45. This is a lively discussion. It seems that many of you are getting caught up with specific definitions and ‘ideal diets’. The concept of the paleo diet might hold some water but it is somewhat irrelevant.

    There is plenty of modern scientific research examining all different kinds of diets…low fat-high carb, low carb high protein, IF etc…there is a good body of research indicating that people can do very well on all different styles of diets…there is also many different types of traditional diets from all 4 corners of the world that work just fine so the concept that there are specific foods that all humans are meant to eat is very simplistic and naive. The traditional diet of someone living in the northen parts of canada (Inuit) is going to be vastly different than people living in brazil, India, germany, the USA or china and so on, based on industrialization, lifestyles, wealth, tradition, religious views, and the foods that are available in those regions.

    This discussion obviously centers on people living in wealthy industrialized countries who have an abundance of food and the real issue is avoiding eating too much.

    Enter the diet and weight loss industry to stop us from following our instinct to eat food when it is present (as I agree we haven’t evolved yet to the point of being able to resist the temptation of food 24/7, but I bet in a few generations we will evloved to be able to handle 24 hour access to food and avoid overeating…either that or the standard human form will just be bigger!)

    So we get a myriad of different solutions pitched to us, from specific nutrient avoidance (carbs or fat) to meal timing, 6 meals per day, IF etc…

    All of this is in an effort to just eat less. Caloric restriction no matter how you arrive at it is beneficial (if you’re overdoing it, which most of us are)…

    it seems so far that IF has some real promise to more health benefits and even some life extension properties compared to other forms of caloric restriction. There is however no strict definition of IF. So really IF is talking about spreading your meals out a bit more, like from every 4 hours to maybe a few 15-24-36 hour gaps every few days. And that isn’t such a big deal really, especially if the preliminary benefits it seems to have in rats happen in humans too…IF might actually be the fountain of youth (combined with weight training that is, there is definitely age slowing properites to weight trianing that I think everyone would benefit from)

    There is no hard and fast scientific proof of the superiorty of any number of meals per day, 1 vs 6 meals per day etc…whatever seems to work for you should be fine.

    I think we all would agree that what we are all looking for is to maintain vigorous health for as long as possible and avoid lifestyle diseases if we can, “Die young as old as possible!”

    And so far many different lifestyles and eating patterns can acheive this.

    John B

  46. I would like to comment on a couple of things. First, I would guess that many people will do well on an intermittent fast despite the studies showing a worsening of insulin sensitivity. Because of biological variability people perform differently on various regimens. The fasts studied were not every other day fasts nor were they even the fast schedules that my wife and I used ourselves. There is some evidence that longer term semi fasts during which regular meals are consumed on one day followed by a 200-400 kcal worth of meals on the next provide more benefit than going totally without food every other day.

    My basic worry is that the process of adaptive thermogenesis – which is indeed real and documented – will lower the body’s set point and make weight loss maintenance more difficult.

    Based on the Paleolithic data, it would seem that early man probably fasted on a regularly irregular basis. If so, the forces of natural selection would have weeded out specimens that couldn’t adapt well to such a regimen, leaving us, who did adapt well. If this reasoning is correct, the case could be made for a day of fasting here and there instead of a regular, clock-work style intermittent fast.

    Tim has asked me what my view is of which part of a calorically-restricted diet brings about the increased longevity. Is it the fat restriction, carb restriction or simple the caloric restriction irrespective of which macronutrients are restricted. The answer to this question can be found in a paper by Gerald Reaven’s group (Gerald Reaven identified and described the metabolic syndrome, which he named Syndrome X) in the journal Free Radial Biology & Medicine. (Here is the URL for the abstract The entire article is by subscription only)

    Here is a quote that pretty succinctly sums up what happens with caloric restriction:

    “…and the radiation-like effect of ad libitum feeding versus restriction of calories but not of essential nutrients in rodents. In the latter circumstance, it is interesting to note that 40% calorie-restricted rodents had a 40% increase in lifespan and that this effect was associated with lower

    plasma glucose and insulin levels and with enhancement

    of insulin sensitivity. In these studies, calorie

    restriction was usually achieved by a 40% reduction of

    both carbohydrates (CHO) and fat while amount of protein and mineral was kept constant. Since composition of the ad lib diet was 21% protein, 60% CHO, 10% fat, calorie restriction mainly entailed an absolute reduction of CHO (rather than fat) intake. For example, if ad lib fed rats had a dietary intake of 10 g/d, quantitative proportions of CHO, fat, and protein were, respectively, 6, 1.2, and 2 g/d; with 40% calorie restriction, reduction in CHO intake was therefore 5-fold greater (from 6 to 3.6 g/d: 2.4 g), than that of fat (from 1.2 to 0.7 g: difference = 0.5 g).

    Therefore, in rodents, a 40% greater CHO intake had

    a radiation-like effect with development of premature

    cancer, heart and kidney failure, and consequent short-

    ening of lifespan.”

    At least from the perspective of Reaven’s group (and Reaven isn’t a fan of the low-carb diet) it is the carb restriction that makes the difference in the caloric-restriction model.

    Tim also asked about differences between men and women as far as hunting and gathering. Some people reason that since men were the primary hunters, that men would mainly eat meat and would eat only after kills whereas women, who were primarily gatherers, ate throughout the day. This may have been the case when we were all still living in Africa, but not since we moved to more northern latitudes where gathering is difficult, if not impossible (especially during the Ice Age), for at least half the year. In these climes women would have to rely on hunted meat as did the men. We also have to remember that much of the gathering women did was of clams, oysters, insects, small animals (rodents, rabbits, etc.) as well as roots, shoots, nuts and tubers. These circumstances lead me to believe there is very little difference between the metabolic physiology of men and women where diet is concerned.

    1. Very belated comment on an old post, but the idea that big prehistoric man went off and wrestled beasts to the ground with mbaky bare hands while the wimmin and chilluns picked berries was a fantasy by early anthropologists. Everyone hunted, it looks like from more craeful analysis of early sites, usually using snares and traps. Please don’t hit the dainty woman eats salad sexism in IF land, too!

  47. Calorie Restriction relieves depression and anxiety! Kind of the opposite of what is said in the above post LOL. 😉

    It is true that the majority of people that do CR are incredibly happy people and not aggressive.

    Lutter M, Krishnan V, Russo SJ, Jung S, McClung CA, Nestler EJ.

    Orexin signaling mediates the antidepressant-like effect of calorie


    J Neurosci. 2008 Mar 19;28(12):3071-5.

    PMID: 18354010

  48. There’s a lot of interesting info out there these days about intermittent fasting and paleo-style diets. Here’s some before and afters for a 54-year old guy who went from a body-building style diet/regimen to one based on a Paleo-style diet with intermittent fasting:

    I don’t know about all the scientific studies, but based on what I have seen recently, these types of regimens are worth a try. And it seems that people such as the one depicted are getting their results not on an overly strict total-fast-every-other-day regimen, but on what Michael Eades suggested in his March 11 post:

    “There is some evidence that longer term semi fasts during which regular meals are consumed on one day followed by a 200-400 kcal worth of meals on the next provide more benefit than going totally without food every other day.”

  49. Some food for thought:

    Is it possible that our current rate of thermogenesis is artificially high BECAUSE we eat so much, and so regularly? I mean, if you think about it, super-obese people (300+ pounds) eat the amount of food in one sitting that an individual of much lesser weight eats in a day, and often what a person of healthy weight eats in a week. I would think that the rate of thermogenesis would depend on the food the body is accustomed to receiving, no?

    If this is the case, that people nowadays have a higher rate of thermogenesis than paleo man, is it POSSIBLE that this is the very cause of many diseases we face today? You know, attributable to increased cell turnover or some such?

    Naturally, I am not a doctor… Just someone who has been a natural IFer since I was VERY young, and am healther than anyone I know. I eat when I am hungry, which is about two to three times per week, usually only one meal on those days, often a low-carb meal. I’d estimate that in one week I eat about what the average low carber does in two-ish days. My rate of thermogenesis is undoubtedly EXTREMELY low. But I suspect it was low when I was BORN, which is why I had a weight problem in the first place. I do know that if I eat every day for a month, I can EASILY gain fifteen to twenty pounds or more, but to do so makes as little sense to me as fasting does to someone who eats regularly.

    For what it’s worth (and not having participated in any formal studies) as a natural IF’er eating largely low carb (meats, eggs) and raw fruits, veggies, nuts/seeds, I don’t get sick (no colds or flu for the last 8 or so years), my weight is healthy, my muscle tone is INCREDIBLE for someone who literally does nothing all day. I have been IFing for about 10 years now, and the last cold/sore throat I had was near the beginning of that.

    Again, not trying to prove a point, just offering up some food for thought and experience. 🙂

  50. Interesting read. Like other posters above, I was wondering why you ate high-carb foods every other day instead of combining IF with the paleo diet. That seems like something I’d be interested in trying next.

    Currently, I’m doing a low-carb CR diet experiment (read more here: We’ll see how it goes, but right now I’m absolutelu starving, and IF sounds a lot easier.

  51. Dr. Eades points points out that IF does not help you lose weight perse because of a decrease in thermogenesis. But, I think the decrease may be a good thing for long term health. I would equate it to running a car engine at a higher than needed RPM. You will burn more fuel in the sort term, but you will decrease the life of the engine.

  52. Thanks Tim ~ I just bought your audio at B&N. I was amazed while listening – this sounds like exactly who I am and how I’ve lived for the last 20 years!

    I’ve been a serial entrepreneur that only works when I choose. I earn lot’s of money and take about 10 months off each and every year. I love that because my wife and I enjoy being parents to two wonderful boys.

    Teaching business owners and entrepreneurs is my absolute pleasure in life.

    To higher profits,

    Bill Covert

  53. “If people increase kcal out by exercising, they end up increasing kcal in because they eat more. It’s called working up an appetite. And since exercise doesn’t burn a whole lot more calories than simply sitting on one’s butt, it doesn’t take a lot of food to compensate.”

    I have to disagree with this, I can easily burn an extra 900 calories an hour while running or 700-800 while biking.

  54. Tim,

    I have been doing a flexible version of Intermittent Fasting on and off for about 5 years. I am someone who enjoys good food and good beer and this is a way for me to enjoy good food and stay around 8% body fat year round.

    What I like to tell readers on my site is to attempt to eat their main meal at night. To burn a lot of body fat they can do cardio about an hour before their meal. Going into a workout in a fasted state works wonders to attack “stubborn body fat”.

    I also tell people to be flexible with this, just try to do it 5 times per week. If they are extremely hungry to eat an apple. I also find that sipping on green tea helps with hunger pains.

  55. To quote Dr. Eades:

    “My basic worry is that the process of adaptive thermogenesis – which is indeed real and documented – will lower the body’s set point and make weight loss maintenance more difficult.”

    Preventing this is what Joel Marion talks about in his Cheat to Lose Diet book and various articles; the appropriately named ‘metabolism reset.’

    Perhaps a period of a few months on IF, followed by a overeating period that lasts for several days or up to a week (or maybe just one day, as Joel specifies), would assist in raising the set point of the metabolism when it starts to slide?

    And what are the best ways to know when the metabolism is slowing? I’ve heard that measuring your body temperate immediately after awakening is one way.

  56. I do VLCD 4 days and I super high calorie diet every 5th day. I am 5 ft and 103 lbs. This is my lowest weight ever including high school and I am 50 years old. I have been maintaining for 5 months. To me it is similar to intermittent fasting as 650 calories is almost fasting I would say 😉 It seems to work even though I eat the house down on day 5 more or less. On day five at some point I become more thirsty that hungry and cannot keep eating. I eat mixed carbs/protein although day 5 seems to be more carbs–but whatever I want. I find I need that really full feeling and the psychological reward of no foods barred. Day 1 is easy–not hungry really. Day 2 is okay and day 3 is okay. Day 4 is trickier. I weigh every morning except the day after–don’t need that info 😉 I find my brain tells me when it is time and I cannot argue with it. Day 5 is not an option. I think this works because I do not feel deprived. I like to bake and I freeze what I make for myself for day 5. It is delayed gratification not no gratification. Plus, I enjoy feeling stuffed. I really do. It has a kind of comfort. Well, okay sometimes discomfort too but it is fun. Good luck to all in finding your way.

  57. My life is definitely an IF life and your first article was quite interesting, as was this one. Only because i know plenty of people who IF and none of them complain about no weight loss or feeling worse, everyone feels better and were all very healthy and work out regularly.

    Most everyone i know who IF’s eats one large meal a day around dinner time. Making sure to work out before dinner so your work-outs aren’t more challenging. (because after a large meal, or any semi high calorie or dense meal,clearly your going to be sluggish).

    Give it about 5 years until everyone is eating this way when they realize the health benefits.

    read up


    look up

    Mr. Ori Hofmekler

  58. To be honest, I believe in IF:

    1. Never seen as much weightloss as doing early morning HIIT and having one low GI meal at around 8PM.

    2. I train better on an empty stomach.

    3. Move around, do stuff, no need to eat.

    IF is not a fad. The studies have been around for a while, there was a rather obscure Spanish study done in the 1950s which contended that TB patients placed on a IF type diet showed significant improvement compared to those on a normal diet.

    Later on, in the 1960s there were a number of studies carried out in Eastern Europe which suggested that the body is in a more adaptive state when injured or fasted. The benefits of this seem obvious with regards to the CNS, and Abadjiev (famous Bulgarian weightlifting coach) was inspired by it to create perhaps one of the world’s hardest training philosophies around. Many a Bulgarian weightlifter has set a world record on an empty stomach.

    Similarly, most of the world’s toughest battles have been fought on an empty stomach.

    I must also say Dr Eades’ perspective is somewhat limited and somewhat confusing:

    So if a calorie isn’t a calorie then why are we talking about calorie restricted diets? Or lowering the amount of calories consumed in a given period? Should we not think of this in terms of insulin response? I can only eat 400kcal one day, and that could be a bar of chocolate.

    And also what about the effect of fasting on the body? It is a very efficient way to detox. It has a great effect on the skin and hair.

    I also find that the whole 24 hours without eating business is too damn academic. In nature that would never happen, the tribe (because man does not live alone but in tribes) would be divided in such a way that there would always be food to eat at night. Primitive societies still work like this.

    There isn’t much else to say really. i have tried having breakfast, and not having it; eating 1, 2, 3, 4, 5 and more times per day, not having dinner, not having lunch; and thus far this is the best approach to eating I have yet to see, the most practical, effective, and (judging by body comp changes) healthy. I might change certain things if you want to put on some muscle (train in the morning, then eat all day and go to bed early, I have yet to experiment)

  59. Given the scaling laws between mice and humans, isn’t one day off / one day on for mice equivalent to something more like one week off / one week on for humans?

  60. Intermittent fasting is an amazing tool to reset your body and remove yourself from the idea of food addiction. Not “having” to eat all the time really gives you a lot more peace of mind and helps a lot with stress. I wrote a review about the book Eat Stop Eat on my site as I highly believe in its methods.

    Unless you have diabetes or some serious health issues I would recommend everyone try at least a twenty-four hour fast, you won’t regret it.

  61. I prefer doing the 24 hour fast. Actually going 20 hours with a 4 hour eating window ruins my evening supper appetite. I don’t eat as much at supper time doing 20/4 and I think that my husband would rather see me eat a little more heartily in the evening. I sleep better doing the 24 hour fast. I have done 20/4 hour and 24 hour fasting for nearly 2 years on a regular basis and I recommend it. I have more energy,more rested, less stressed. BTW, It got me back on track with my low carb lifestyle and I lost nearly 25 lbs. with very little effort.

  62. I read this article with interest recently, after someone found it in an internet search and asked me to read it. I think there’s a lot of assumption in your comments and they almost seem to be misleading. I’ve used intermittent fasting over many years and so have a lot of others and I have yet to come across any of your so-called many studies showing negative effects of IF on metabolic profile. I have an incredible metabolic profile and there are positive human studies going on. Please let us have detaisl of these numerous negative studies. Are you referring to anecdotalm web comments by people who use this eating method then eat an extremely unhealthy diet?

  63. Most people involved with Calorie Restriction are doing so with low-carbs – eat the least amount of the best nutriments and absolutely no empty calories.

    So the intermittent fast (IF) is going in the wrong direction in the first place.

    Calorie restriction does work – and wonderfully so, please look up forums – one of the key factors is training your system to go progressively on an extented time/hours without food.

    For example the easiest way to understand and practice is: eat dinner as early as you can, and delay the first meal of the next day as much as you can. Try to extend that time..

    But forget the macaroni and cheese.!!.. that’s not even in the picture, if you’re doing CR, you are on low carbs anyway. No gorging either.

    The beauty of it .. it’s gets easier and easier, you feel ..great, you sleep deeply….

  64. It’s been a while since that article was originally submitted. It’s been interesting to watch the comments cascade.

    I am utterly convinced that Dr. Eades’s conclusion to what he wrote was a cop-out. I think the bug of the “medical establishment” is firmly in his ear.

    IF has tremendous benefits — and equally tremendous variability. Start testing yourself.

  65. As a Muslim, I do believe that fasting is good for the body and soul, since God created us and if i believe that islam is HIS message then I believe HE knows what’s best for me.

    Here’s how we fast, for research purposes, so you guys can compare it to IF:

    In Islam fasting is from dawn till sunset, no food or drink in between. It is recommended by the prophet Muhammad (whose actions we are ordered by God to emulate since he is the example for us) to eat as close to dawn as possible before the fast starts and then again eat right after sunset and not wait too much to break the fast even if we eat something small like a date.

    1. We fast everyday for one month a year, Ramadan. That’s 29-30 days depending on the lunar calendar. Fasting this month is mandatory for all Muslims.

    2. Then comes volunatry fasting. We can follow the examples of the prophets Muhammad and David and fast extra days. We are rewarded hugely for each day of voluntary fasting..

    – The prophet fasted on Mondays and Thursdays every week of the year and he also fasted lots of random days every month in addition to that. We are recommended to follow his example but it is not necessary at all to fast except for in Ramadan. Still lots of people do fast Mondays and Thursdays and random days of the rest of the year as well.

    – The prophet told us that the best fasting is that of Prophet David who used to fast every other day. Some Muslims also emulate this, though its much harder.

    While i was reading the article I thought this way of fasting would be interesting to compare to IF 😉

  66. The big insight for me is that weight loss is no longer the main issue. It’s all about being healthy. Fasting is healthy if you have to clean up. Once clean, you can stay clean for a while if you cut out the processed foods.

    I just love the scientific approach to these things. The idea that I can start up the CMA process to clean up my mitochondria gives me a feeling of control.

    I don’t need to eat everything all the time. But when I am dining in a restaurant, I don’t want to push the potato’s off the plate. And I do want some garlic bread. And I do want some good wine.

    Flexibility and control is what I need to stay healthy and lean ánd enjoy life to the full. Dr Eades set me on the right track, and I am eternally gratefull for that.


  68. Hi, I have been doing a version of IF for 2 years now. I do this on a daily basis and I am so glad that there has been studies done on this. For many years I considered this evil and supportive of the anorexic lifestyle.I now realize that I was eating too frequently and my whole day was spent on what to eat next. One thin nice about IF is it makes it so easy to know exactly what I want to eat.

    I fast for 20 hours then enjoy a 4 hour feasting window. Well, at least my first meal is a feast…subsequent snacks and meals are comparatively small. I have come to the point where I sometimes eat only once a day. My diet is low carb which works hand in hand with IF. Both are ketogenic so you are receiving ketones needed to maintain healthy muscle, and cell tissue. IF gives your innards time to rest and regroup. This is how I see it through my experience with IF. I don’t think that our bodies are equipped to take on the daily riggors of 3 meals a day with in-between snacks.


  69. Well, I have been inlcuing IF with my low carb lifestyle for over 2 years. I have enjoyed a loss of around 24 lbs which is only 12 lbs a year. I feel good and will be visiting my doctor today for his input. I don’t know where he stands on this type of combination…or even low carbing. So I made a synopsis of my dietary plan. I included a list of nutritious food that I consume.

    I basically fast for 20 hours and eat within a 4 hour window. It’s possible that varying fasting styles add to the success and/or failure to IF. I also added a few cycles of jogging to prepare for a 5K run.

  70. I was again recently prompted via a visitor to my site to see the progress of this debate since my last comments in January. Nice to see the responses to this article (that have gone on for over a year now)! I’m not surprised most of them are positive and in line with my own views.

    There are numerous ways of doing IF and it is now well known that a number of top athletes are using IF very successfully. As a well known martial arts conditioning writer and martial artist myself, I (and many others) have had very good results with IF. My interpretation of the research data out there is that IF is mainly a form of Caloric Restriction (CR) which trains the body to run on free fatty acids (and to secrete less insulin as a result).

    That reduced insulin secretion and the running on fatty acids – instead of glucose – is probably responsible for the elevation in insulin reported in the negative article which prompted these posts. However, its not a negative thing in itself and the blood glucose elevation is never high enough to be regarded as worrisome hyperglycemia. IF users will have a different blood profile to multiple feeders, but that is because they eat differently. Health should be assessed objectively and not just against rigid criteria aimed at a specific demographic.

    Slightly raised sugars during fasts are normal for bodies well adjusted to IF, but are not unhealthy in those circumstances. A similar example of blind adherence to pre-set charts is the way that an athlete has a relatively high BMI measurement – which is bad, according to the charts. High BMI is bad for an inactive, overweight person, with high body fat composition – but not for a lean athlete, with big muscles (who then becomes too heavy for his or her height according to BMI measurements). Similarly, slightly elevated blood sugar is bad for someone eating 3-6 times daily, but not for someone who fasts intermittently.

    Note that not all fasting methods produce this effect of slightly elevated sugars to the same extent – mainly, daily fasting protocols do this more than less frequent fasts. But it probably happens for a period during all regular fasting of any type.

    One additional value of IF – which accounts for the reason why it still gives the same benefits of CR, even when calories are not actually restricted – is that it appears to activate gene expression of ‘healthy genes’ which prolong life. That’s why animals using IF (but still overeating) share the same extended lifespan benefits as the animals on CR. THE GENES PREVENTING DISORDERS THAT CURTAIL THE MAXIMUM POTENTIAL LIFESPAN ARE EXPRESSED BETTER DURING FASTING PERIODS. I BELIEVE THAT IS THE MAIN ADVANTAGE OF IF OVER NORMAL CR. The fasting period is crucial for awakening the life-extending genes most animals have in their cells at various degrees of expression.

    Having said all this, although doing IF and using what we’d call the ‘average’ Western diet is still effective – one should only expect to get down to about 10% bodyfat (lower if you have extremely big muscles – but remember the bigger muscles just add weight so that the percentage of your body weight made up by fat is ‘mathematically’ lower – but the actual quantity/weight of body fat is not necessarily changed). e.g. If you have 16 pounds of body fat and weigh 200 pounds, you have 8% bodyfat. Increase your muscle mass by 20 pounds and you weigh 220 pounds. But the body fat still weighs 16 pounds. That’s a lower body fat “percentage” but not actually lower fat levels – beware of stats and body fat measurements, they can never be really accurate and mainly are informative when only one parameter change is made in your regime and looked at comparitively).

    Still, 10% is low enough to be defined – maybe not quite ripped though. I usually get down to 8-10% using IF, but without particular focus on quality of diet. I’m not particular about being ‘bodybuilder ripped’ as my training is mainly for functional and health purposes, but I don’t think it would be hard to minimise bodyfat by cleaning up my diet. However, that ‘cleaning up’ act would be a miserable experience, wouldn’t it?

    To get to minimum possible body fat (really, that’s about 5% on any of the standard measuring systems) you would need to be as careful with what you eat as anyone else following the multiple meal philosophy (such as bodybuilders). Not for me at this stage, but maybe in the future. Surely, 8-10% is good enough for most of us – isn’t it?

    Idai Makaya

  71. The role of growth hormone seems to be completely lost in the above article. It may be inevitable that any form of calorie restriction will lead to reduction in thermogenesis. I have only my own experience with IF to consider that possibility. I may have experienced some reduction in thermogenesis myself with IF….but I have found that IF is the easiest method, from a behavioral standpoint, to create a calorie deficit. Also, just stop IFing and then resume IFing when your thermogenesis level goes back to normal…if that actually happens. This lower metabolic rate thing seems to need just a few weeks to correct. IF Stop IF.

    However, Eat Stop Eat protocol requires strength training in addition to IF…a huge metabolic difference. Properly performed strength training which is extremely rare (effectively unknown), especially among medical/university personnel, is by definition, “a shot of growth hormone”. This would dramatically alter the metabolic situation from simple IF alone….many studies support the crucial role of growth hormone in regard to fasting safety and effectiveness.

    My experience with the benefits of strength training is more than extensive. If diet is a common factor, effective strength training always makes a huge difference in fat loss regardless of diet.

  72. Well, for me these theories are kind of crap.

    I don´t need to be a scientist to say this studies are somehow false in real life, and we see it everyday.

    Hmm … Let´s see .. Caloric restriction makes you live longer and healthier? What the hell?? Some starvation and low food income makes your body better? I surely don´t believe that, and I don´t know why those studies drove to that conclusion! So these are for me some simple contradictions in that theory:

    – What about abandoned dogs, living in the street? They eat less then domesticated dogs .. but they are unhealthier, more likely to develop diseases, and die sooner;

    – What about people in undevelopped countries? Excepting extreme cases (like subsaharian africa, where they only get carbon hidrates diet) this persons have a low calory income, and a varied diet, but they surely have a life expectancy smaller then wellfed high caloric develloped countries?

    – What about vegetarian people? They eat few calories, but they seem skinier and unhealthier then people with a normal caloric diet;

    – what about physical activity? With low calories your body won´t have energy to perform them, and not performing them equals to not have all the health benefits from them.

    So unless there´s a study that proves me, like 1+1=2, that this diets really get to their point in humans, I´m not buying this.


  73. Well, there are articles posted about this every week if you care to read them. Here is a new one for you.

    I am sure you can find others if you are interested. Scientists have been studying this for decades and the original theory is ancient.

    It was a hot topic with Luigi Carnaro in the 15th Century. Here are some modern (like1833 and 1913 reprints) of his experiences:

    Of course there were questions back then about whether the world is round.

  74. March 3rd, 2008

    6:31 pm

    Didn’t paleolithic man have a lifespan of like 40 years?

    He didn’t die of ill health if that is your drift.

  75. With the whole 40 year paleolithic longevity issue… if primal man had access to the housing, medicine, and sanitation of today–he would have lived much longer, it just goes without saying.

    It’s impossible to disprove the effectiveness of a theory such as the paleolithic lifestyle with an outlier such as that (it’s just a blanket statement not considering other advances, not to mention epigenetics) …

  76. Okay, throw away observations of how people lived and survived hundreds of years ago. I chose to become the guinea pig in my own intermittent fasting experement.. In April of 2010, i will be doing IF for 3 years. All I can say is it gets better the longer I do it.

    I consider my lifestyle the modern paleo lifestyle. I’ve lost 35 lbs. I live a low carb/ketogenic lifestyle that consists of 1 to 2 meals a day. I eat lots of saturated fats, nutrient dense low carb fruits and veggies. I especially eat meat. I eat like a lioness. Now that is what I call research I can use.

  77. Idai, just read your post with much interest. I just had a glucose tolerance test this week. My glucose rose considerably and I am expecting my doctor to diagnose me as being pre-diabetic. I felt that my results may cause some concern yet I was not concerned about it because I fast. The more I read about this the more comfortable I am with my GTT.


  78. This study and his view is based on trash. First, he’s not looking at what the people ATE. Of course, if you eat cheesecake, meat, candy, etc. then fast, you will get bad results long-term – however, many benefits result from fasting anyway. But if people eat a raw vegan diet – then fast, they’ll get amazing results and improved health with the added benefits of fasting. It just amazes me this ‘doctor’ is so full of crap haha

  79. IF works. I do not or ever will again eat any grains such as wheat or corn and avoid all forms of soy and veg oils. IF works wonderfully with a low carb diet- Id be careful with total raw vegan diets as they are totally incomplete in nutrition. Vegatbles are a very important part of a low carb diet but animal protein still ranks as the best food choice.

  80. I think a modify version of IF works – and perhaps is the best way of eating. If you look at for example Hurtado and Hill, two anthropologists who have lived among the Ache people in Paraguay, they find that they ate ca. 95 percent of the food in evening. The women maybe a bit less. The same have been reported by Krogh and Krogh 100 years ago. I have been well trained my whole life, doing competition both in bodybuilding and powerlifting, but two years ago I decided to get mye daily, off-season fat percent down from 12 to 9. The only thing I did, was to start eat 60-75 percent between 18-21 (although just one meal), and the rest in two small meals – 08:00 and 13:00-14:00. Just in 2-3 months I reach my goal.

    If we look at the studies from Mattson et al and Varady et al, it’s perhaps better to eat something every day on IF, and a high fat diet is better than a low fat diet.

  81. I eat a high fat diet. I was already doing low carb. I increased my fat intake. If I had my druthers, I druther eat one meal a day all the time but right now, I will throw in a couple of days a week where I do eat one meal. By far, keeping your diet rich in fat and protein and all the nutrients that comes with that is ideal. This is just my opinion but fasting is ketogenic so why not fire the ketogenic fires with ketogenic fuels namely fats. I know you are speculating that I eat a vat of fat which is untrue. I just make sure that I have some form of fat ( butter, cream, coconut oil,omega 3s, MCT oil ) throughout my day, even while I am fasting.

  82. It used to be a very popular part of detoxifying and health regimes to incorporate fasting. However the newer approach is to have adequate amounts of amino acids, minerals, and essential fatty acids to drive the natural detoxification mechanisms in the body.

    With a lack of essential nutrients, more toxins like various heavy metals are retained versus being shed. In addition to ensuring that patients have adequate nutritional intake, it also can be very important to use natural medicines to facilitate detoxification pathways from the liver, intestines, or lymphatic system.

  83. Low calorie diets and fasting have interested me for many years. There is a lot of studies that correlate longevity with low cal diets. One of the main researchers I have found to be helpful was Edward Howell M.D. and his work on enzymes.

    Some of the studies on animals show that the ones who eat raw food diets versus completely cooked or enzymes-less foods have longer lives and less disease. Animals on the all cooked food diets had more pathology in various organs like their pancreas.

    Dr Howell hypothesized that when a diet that included a large percentage of raw food, the naturally occurring food enzymes would break down a lot of the food eaten, so that the pancreas would not have to work as hard to produce enzymes to digest food. Dr. Howell thought that the digestive system may be over worked from having to digest such a large percentage of our total calories. It was thought that the digestive system might rob nutrients from other systems just to keep up with the over worked system.

    Our eating habits have radically changed with modern food processing were enzymes are taken out of food to give longer self life. Dr Howell thought that it was impractical for the average person to eat a raw food diet, so he created the 1st digestive enzyme supplement to digest the food before it reaches the small intestine to signal pancreatic enzymes.

    After studying Howell`s work and others and seeing my own blood under a microscope before and after eating meals with and without enzymes (not pretty), I have been a big believer in daily enzyme usage.

    I also think the total caloric load, quality of the nutrients, and health of the persons digestive system influences the amount of free radical chemicals created from food that potentially creates disease in the body and possibly shortens life span.

  84. Hi David Majercin,

    Yes , I agree,you must make certain that your diet supports your fasting regime. If you are taking in proper nutrients, you should not need medication. Your body is perfectly capable of running itself quite well in nutrition is optimal.

  85. Ha, I love where you split the text in two parts .. what a contrast 🙂

    Even though I don’t “have a thing about seeing my grandson grow old” (song) I certainly want to live a healthy life and not become a burden to anyone. While reading the posts I was thinking whether there are studies about the Ramadan fast and sure enough I found a few that study the effects on serum glucose and the lipid profile. A thorough and large-scale study is still missing though.

    Unfortunately, the good effects of the fast are hampered by unhealthy eating habits of the societies throughout the Muslim countries. I’m excited for this year’s fast, because 1. it will be in summer and therefore more challenging and 2. it is the first Ramadan after I switched to a more healthy diet without processed foods. My ultimate goal would be to continuously fast for two days every week after Ramadan. That way the health benefits would be more constant .. not that we fast for the health benefits of course. It is an act of worship and the benefits are a nice bonus.

    I couldn’t agree more that it is a very liberating exercise. And also a very good practice for disciplining the lower self.

  86. Not sure if anyone has mentioned Martin Berkham over at His method of IF has shown real world results to the contrary of this article. I’ve never seen people so ripped eating basically whatever they want. Of course, they actually work out over there…I’m pretty sure their blood work is good as well.

  87. thanks for the article ! i hope to try this intermittent fasting plan. I was thinking of only having breakfast (a substantial one) then fasting until breakfast the next day, but I do like the 6pm idea. You and your wife seem like a cool, health conscious couple !

  88. Intermittent fasting should be 8 hour eating window followed by 16 hours of fast (8 of which are sleep).

    This diet works, reverses aging, makes you go down to single digit body fat and stay there very easily.

    If you want an extremer version you can go with the Warrior Diet, which is 20 – 4. I like the mindset of warrior and can really resonate with the fact that our ancestors hunters/warriors ate only one big meal at evening. And in the day it was necessary for them were on high alert to catch prey or fight enemy. Which is impossible by eating breakfast, launch… Just makes you lazy and sit around.

    I’ve followed the slow carb diet and it was mentally more challenging than intermittend fasting. I was always hungry and it was quiet inconvenient.

    I will probably stick to intermittent fasting as long as I live.

    Stay strong.

  89. wow, It’s been 5 years since I have been doing IF. I have changed it a bit as I have adapted to it. I now eat mainly once a day, low carb, high fat, moderate protein. I manage to keep my blood glucose at normal levels and know what to do if the levels change.

  90. Dear Tim,

    have you heard of Aubrey de Grey’s work? He has this great Ted Talk where he shares his goal of ending aging altogether. I think this guy is on to something. I HIGHLY recommend you check out his work. He is the founder of the Methuselah Foundation and he is a real visionary. Also, look into SENS for some more information on life extension that is out of this world.



  91. Brain scan shows tha braincells startsnew production and repairs of cell starts but how long fast before that happens in the fast was not revealed…but Im looking for that fact now!