Marks Daily Apple
Serving up health and fitness insights (daily, of course) with a side of irreverence.
9 Aug

Is Intermittent Fasting Healthy?

If only I weren't so skinny!

One thing is certain in the field of health: what is common wisdom today can easily become “misapplied science” tomorrow. What’s “in” this year may be “out” next year. Often it’s hard to arrive at the right answer.

For example: Oily fish is good for you because the Omega-3’s are so healthy, but oily fish is bad because it can be contaminated with heavy metals, but oily fish is good because recent tests prove it’s not actually very contaminated, but oily fish is bad because the fishing industry paid for those tests…you get my point.

The Fats vs. Carbs argument is another. So when a reader recently asked about regular fasting as a means of maintaining good health, I had to re-evaluate my point of view slightly. What I found surprised me and convinced me to add a new twist to my ongoing health-and-anti-aging regimen. It’s called Intermittent Fasting – or IF.

Twenty years ago, as I was first forming my Primal Health point-of-view (based on a model of how humans evolved), I found it very easy to embrace the concept of “grazing” that seemed to represent the collective conscious of the weight-loss-and-health movement at the time. After all, eating several small meals a day – grazing to maintain even blood sugar and to avoid having your body go into starvation mode and start hoarding gobs of fat – seemed to fit my picture of early humans roaming the plains of Africa foraging for roots, shoots, nuts, berries, grubs and the occasional road-kill leftover from a hyena feast. The explanation that we in the weight-loss business gave the public was that by maintaining this steady supply of protein, fats and carbs throughout the day we would never experience a wild swing in blood sugar due to rapid rises and falls in insulin, therefore we would be less inclined to store fat and more inclined to burn off our existing fat stores. Heaven help us if we skipped breakfast, overate or starved ourselves periodically. That would surely wreak havoc on the delicate hormonal systems keeping us in homeostatic balance.

Well, maybe not.

The truth is, many people have succeeded in losing weight and keeping most of it off using this simple grazing method, which consists of eating 5 or 6 small meals or snacks spread evenly throughout the day, with no single meal exceeding 600 calories and where each meal or snack contains a little protein. This grazing method is the ultimate in portion control: take the 2400 (or more) calories you might otherwise scarf down in 2 meals and simply spread them evenly throughout the day. I think it’s reasonable to project that many more have avoided or postponed getting type 2 diabetes using the same method.

But like many behaviors in the fitness and health world, there comes a point where the benefits decrease and we find ourselves on the dreaded plateau.

The first thing most people will tell you about their attempts at grazing is, while it usually works well if you are diligent, it’s pretty difficult to stick with, since you need to be near a source of quality food every few hours. If you work at home most days as I do, it’s not a problem, but it can make life difficult if you work in an office setting or happen to be a road warrior.

The next common issue is that after a few months of progress, you arrive at a frustrating point where the weight stops coming off, the initial high energy levels decline or you stop building muscle. That makes sense from an evolutionary perspective, since the body is so well-tuned to adapt to any situation – including a perfectly even flow of nutrients. In this case, the body’s reaction to this steady supply of nutrition is to actually decrease insulin sensitivity. It “knows” there will always be food, so it “down-regulates” insulin receptors, and probably down-regulates other metabolic systems as well.

In my Primal Health articles here at MDA, I am always looking at ways we can harness our DNA blueprint to maximize health. I like to see how we can shake things up a little and trick the body into burning more fuel, creating more lean muscle, repairing cell damage and staying injury- and illness-free. So when my 79-year-old buddy Sid at the gym started raving about his weekly 24-hour fast over a year ago, and my friend Art started writing about his own fasting experiences, I decided to look into it further.

The results were surprising and impressive.

Numerous animal and human studies done over the past 15 years suggest that periodic fasting can have dramatic results not only in areas of weight (fat) loss, but in overall health and longevity as well. A recent article in the American Journal of Clinical Nutrition gives a great overview of these benefits which include decreases in blood pressure, reduction in oxidative damage to lipids, protein and DNA, improvement in insulin sensitivity and glucose uptake, as well as decreases in fat mass.

How can you argue with results like these? And it all makes sense from an evolutionary perspective, because our predecessors almost certainly went through regular cycles where food was either abundant or very scarce. The body may have established protective mechanisms to adapt to these conditions by sensitizing insulin receptors when it was critical that every bit of food be efficiently used or stored (as in famine), or by desensitizing them when there was a surplus, so the body wouldn’t be overly-burdened by grossly excessive calorie intake.

Beyond insulin sensitivity, it appears that caloric restriction and intermittent fasting may “turn on” certain genes that repair specific tissues that would not otherwise be repaired in times of surplus. One could surmise that this adaptation serves to allow certain cells to live longer (as repaired cells) during famine since it’s energetically less expensive to repair a cell than to divide and create a new one. That might help explain some of the extended longevity seen in animal studies using caloric restriction and/or intermittent fasting (read about here, here, and here). Intermittent fasting has also been shown to reduce spontaneous cancers in animal studies, which could be due to a decrease in oxidative damage or an increase in immune response.

So, what are the practical applications of this research?

It depends. There’s probably no right answer (remember what I said at the beginning!) Art suggests mimicking the experiences of our ancestors, which is to say don’t plan any fast, just surprise your body every once in a while with 24 hours of little or no food. My friend Sid does his fast every Tuesday like clockwork, so he has a light final meal on Monday night and doesn’t eat again until Wednesday breakfast. He does drink water and a little juice on his fasting day. Some fasting programs suggest you take a two-week “cleansing” approach where you eat regularly every other day and fast (or eat 40% of normal) on alternate days for two weeks twice a year.

One thing that is most interesting about the intermittent fasting studies is that slightly overeating on the non-fasting days (to make up for the lack of calories on fast days) yielded similar results, so it wasn’t so much about total calories as it was about the episodic deprivation.

As for me, I’m going to try the once a week deal, but I’ll start by no longer agonizing over a skipped breakfast or late dinner. What I used to think was the end of the world might just be the beginning of a new one!

Let me know of your own fasting experiences.

UPDATE: See this post on Women and Intermittent Fasting.

Further Reading:

My Carb Pyramid

Healthy Recipes

Sponsor note:
This post was brought to you by the Damage Control Master Formula, independently proven as the most comprehensive high-potency antioxidant multivitamin available anywhere. With the highest antioxidant per dollar value and a complete anti-aging, stress, and cognition profile, the Master Formula is truly the only multivitamin supplement you will ever need. Toss out the drawers full of dozens of different supplements with questionable potency and efficacy and experience the proven Damage Control difference!

Subscribe to Mark’s Daily Apple feeds

You want comments? We got comments:

Imagine you’re George Clooney. Take a moment to admire your grooming and wit. Okay, now imagine someone walks up to you and asks, “What’s your name?” You say, “I’m George Clooney.” Or maybe you say, “I’m the Clooninator!” You don’t say “I’m George of George Clooney Sells Movies Blog” and you certainly don’t say, “I’m Clooney Weight Loss Plan”. So while spam is technically meat, it ain’t anywhere near Primal. Please nickname yourself something your friends would call you.

  1. I used to do (once upon a time!) papaya juice fasts for 24-48 hours. While my whole system seemed to enjoy the “rest”… I dont think there were any long term beneficial results.. I think intermittent fasting is good for head and heart

    gp in montana

    GP wrote on August 9th, 2007
    • My fasting experience has been successful. I did it three or four time a week. I know some people did it once or twice a week, but still achieving good results. March marks the 5th year of my IF. I lose weight, stay fit and feel much healthier than before. Though more people should go on the IF way of eating.

      Intermitten Fasting Success wrote on March 5th, 2010
      • Just remember NOT to fast right after an intense workout and do give your body a chance to recover completely before start on a fasting program.

        I agree with some of the users in here that drinking juice on a short fast is NOT ideal since your body will think you are on a low calorie-diet instead of really fasting.

        I fast on water/herb teas once a week on a Sunday for 24 hours starting after lunch until noon on Monday. Again, the reason for Sunday since it is a quiet day for me and I have done my intense workout during the week, which my body completely recovered by then.

        I alternated between drinking hot water with lemon and herb teas throughout the day. The kind of herb teas I drink are detox teas like kidney cleanse, liver cleanse, artichoke leaves etc.

        I break my fast with a vegetarian protein shake, which consist of two tablespoons of organic brown rice sprouted powder (85% protein digestibility), two cups of coconut milk, one tablespoon of wheat grass, a large ripe banana or pear and a handful of baby spinach.

        Cheers from Karl :-)

        MrRoberts wrote on June 2nd, 2011
        • Great explanation, thank you so much. I am starting a once a week 24 hour fast. I will be traveling so will bring along teas and citrus for my water.

          Mel wrote on July 27th, 2012
      • Just curious what your IF schedule was like. I just started learning about IF, I would like to give it a try I just don’t know what to do. Thank you in advance.

        Mary wrote on April 5th, 2012
    • This is interesting, because I have always been one of those people who can’t not eat for longer than a few hours. I my stomach would literally rebel if I didn’t eat, and I wouldn’t then be able to eat without feeling super sick and crampy in my stomach. Lately, I have been intermittently going for like 12 hours without eating, because I have time and access to good food in the mornings, (wake up at like 5 for breakfast), and after about 1pm I usually stop eating until 10pm, sometimes I don’t eat from 10 to 10, and I have found that it doesn’t hurt me like it used to any more, and I have been surprisingly ok with it. However, with workouts it seems to make me lag when I haven’t eaten.

      Naomi wrote on July 22nd, 2011
      • I lIke the additions to your book and I lenraed some new things that were very useful.However, I was surprised that you made little mention of autophagy-one of the major advantages of IF. Of course autophagy might mean more to me than you as I am close to 70.I have done a link chase on autopphagy and there is a wealth of information available. Based on that information, I use IF to do cell hardening, strengthen muscle cells and to kill random cancer cells floating around in my body. There is enough information available to justify a chapter in yet another edition in your book when the time comes.Otherwise, congratulations on your great work.

        Giovanni wrote on June 5th, 2012
      • Hi bud just seen comment and taut would give some advise. Most of your IF should be done while sleeping to make it easier and fasting like 16 to 18 hours each day. What i do is wake up skip breakfast like half 2 i hit the gym so i eat a wholegrain bananna sandwich to carb up and have some energy for the lifts , then have your protien and a small dinner and then at half 6 or 7 have your main dinner and thats your fasting done wait until next day to start cycle over again. And like commented above on your off days (non working out) kind of carb cycle so during the eating period avoid your carbs and you can stack up on your juices through out the day while body is in recovery mode. Hope this helps

        Mikie wrote on July 14th, 2012
        • Thank you for your input. Your explanation makes the transition achievable. Just to clarify, is it best to eat prior to a workout to maintain best results? I’m an early riser and prefer my training in the mornings which would be prior to the completion of the fast for that day.

          LaPier wrote on October 23rd, 2012
    • There seems to be a great deal of confusion about the idea of fasting… With the so many variables at work, it seems that one beneficial step for fat loss (fasting after a workout to increase growth hormone release) would also be detrimental for muscle-building/retention (a catabolic state due to muscles being “starved” for food). Perhaps the best approach is to see what works for you, evaluate and measure your progress, and tweak appropriately.

      Abel James wrote on October 19th, 2011
    • The problem with juice fasts is you are still taking in massive amounts of sugar, thereby negating any health benefits

      Michelle wrote on February 8th, 2012
  2. I knew a guy who did a juice fast one day a week. He said it cured his sleep issues and gave him greater mental clarity. Haven’t ever tried it myself. I’m way too much of a foodie. :)

    Sara wrote on August 9th, 2007
    • i had similar results…with 48 hour fast…..There is actually some research that say fasting helps de-calcify the pineal gland….basically helps it reset and get all the fluoride and other crap out of your pineal gland.

      kev wrote on July 4th, 2010
  3. Only problem with a juice fast is that you may be defeating the purpose. Many forms of juice are high in sugar and might lull one into thinking they are fasting when they are not really. I think you have to achieve that true low blood-sugar state to start prompting the desired changes.

    Mark wrote on August 9th, 2007
    • Yes, fasting means water only. The moment you take in any external calories you break your fast. Then it becomes a low calorie diet not a fast. Juices are loaded with calories.

      Faster4life wrote on April 9th, 2011
      • so no Tea or coffee?

        Mary wrote on April 5th, 2012
        • Personally I find that drinking tea (no milk/sugar of course) or black coffee does not upset the fast the way juice or other caloric substances do. I just spent several weeks eating one meal a day (except sundays) and felt great by the end; to help me get through that last stretch before the meal I would drink coffee, and it was a nice boost, didn’t destabilize me like calories did. (I felt especially good the week I did zero grains – my main food was almond butter.)

          Kathleen wrote on April 19th, 2012
      • home-made vegetable juices would seem ok, e.g. cucumber and celery

        cis wrote on July 11th, 2013
  4. I can personally attest to IF working wonders. Most people especially in the gym are so brain washed into thinking they need protein every 2-3 hours or they go into a catabolic state and wither into nothingness. I say the body is smarter than that and can do with what you give it.

    Personally I do a daily fast and only eat from 1-7pm taking in enough calories that I would normally take in and focus on lots of protein, quality fats and vegetables. I mix in some carb up days whenever I need them for a more explosive activity such as playing ice hockey.

    So far I have lost 10lbs of fat, gained 5 lbs of muscle and hover at around 8% BF. I have plenty of energy in the morning to do a strength workout 3x a week and add in some walking and hiking. Needless to say I had to see for myself and I did not lose any muscle during the fast but rather gained and lost fat. I am sure my LDL and BP have gone down, I have more focus in the AMs with only a cup of coffee (and I only need one to last me a whole day) and my life does not revolve around food and I enjoy my meals when I have them.

    Best part is IF is a lifestyle, not a fad fast. You can do a 16-18hr fast daily(like I do, 24 hr fast 1-3x a week, or just fit it in whenever. That’s not even to say the healing powers of fasting go back 100s of years.

    Sorry for the long post, but as a fitness professional and working with many people with chronic illnesses, I can’t stress this lifestyle enough.

    Mike OD wrote on August 9th, 2007
    • Quick question Mike -Will taking ACV with water during my fasting period affect the quality of my fast?? Normally I stick to water and black coffee during my non-eating time, but have been trying to incorporate some ACV into the scheme lately and it suddenly dawned on me that i have NO idea what affect that would have on my blood sugars… thanks!

      Hazel wrote on June 20th, 2012
    • Thank you for the long post mike! I was curious if it was healthy to do this on a daily basis as most posts only seemed to focus on a “once and a while” or once a week basis. As a new father, student, and having 2 jobs, this way of eating is so much easier for me then the every 2-3 hours diet. I started last night, eating a normal healthy dinner about 12-14 hours before I knew I would be training the next day. I must say that I couldnt be more surprised at my energy level and stamina during my intense 12 mile bike and hike.

      I will be sure to post back after 2 weeks with my results. Feeling great right now!

      Thanks for everyones advice and input.

      Jason wrote on August 26th, 2012
    • You sound you got off to a great start. How are you maintaining your goals since this last post? That window for you fast is the one I will try, any tips regarding how to stick to a clean lunch when bringing it from home?

      LaPier wrote on October 23rd, 2012
  5. sorry just to clarify too, it’s not a reduced calorie/calorie restriction diet, it’s just a smaller window of eating with the same healthy calories (within 10%) I would normally intake in a day. Also the fasting is strict water and only coffee for me, no sugar added. I also add in some apple cider vinegar and fresh lemons during the water fasting periods.

    Mike OD wrote on August 9th, 2007
  6. Mike
    That sounds worth it! I believe i’ll give it a try, thanks for sharing how well it works, i’m convinced. Oh, i always drink water with a fresh squeezed lemon after a good work out.

    I have a friend that did drank juice for her fast. She did not complain about being hungry, it didn’t bother her not eating, You’re right, it does defeat the purpose. I told her i did not think drinking juice was a “fast” that she was just sacrificing eating.

    Donna wrote on August 9th, 2007
    • I think that drinking juices and more so mineral based beverages are essential to physical health. keeping in mind that a certain amount of natural sugars are very good for the body. you may choose a more deprivation based fast but the body needs some form of nutrients in order to survive in a healthy manner. I started my fast two weeks ago. I only eat twice a week within a 24 hour basis and plan to go the entire month as a starting point. yes it doesn’t sound but so interminent but i find that my body does need these vitamins. i tried only on water and the effects were not favorable. nonetheless i think anyone at least trying a little deprivation in an overindulgent/obese country is admirable in there actions to break societies’ poor habits. anyway…the fast feels great and i encourage anyone to try as within reason.

      Megs wrote on May 3rd, 2011
      • Megs
        Please be careful. What you are doing is definately not healthy. Even Alternate Day fasting is hard on the heart:

        “This is not a positive report.

        CONCLUSION: Chronic ADF in rats results in development of diastolic
        dysfunction with diminished cardiac reserve. ADF is a novel and unique
        experimental model of diet-induced diastolic dysfunction. [!] The
        deleterious effect of ADF in rats suggests that additional studies of
        ADF effects on cardiovascular functions in humans are warranted.”

        Ahmet I, Wan R, Mattson MP, Lakatta EG, Talan MI. Chronic alternate-day
        fasting results in reduced diastolic compliance and diminished systolic
        in rats. J Card Fail. 2010 Oct;16(10):843-53. Epub 2010 Jul 1. PubMed PMID:
        20932467; PubMed Central PMCID: PMC2953475. ”

        Please, Meg, reconsider and reinstitute at least 5 days per week of 2000 calories. Two days of water/lemon fasting per 7 day period is plenty for quick weight loss.

        Maggie wrote on May 9th, 2011
        • been fasting three days a week for three months– maybe lost a pound. on my eating days, it was maybe 1300 cals of very healthy foods. I run about 10 miles week. I’m about 190 at 5’4″ 34″ waist (rolly polly) very healthy, never get sick— just meant to be chubby I guess? before doing three days a week I was doing two for nine months– didn’t loose then either. I started two years ago with Tuesday fasts and daily 1200 cal days. over two years lost maybe 10 pounds? I’m close to 60, so maybe that’s it? people say I look early fortys, and that’s the way i feel— just thought by now I’d be.., maybe, 170?

          mory wrote on May 16th, 2011
      • That is not the type of fasting we are talking about. Eating only twice a weeks is starvation not fasting; however the compressed eating window or one or two 24 hour fasts thrown into the diet is healthy.

        Furthermore, your dogma sounds extremely pro-ana to me, being a recovered anorexic(26,4’7,134lbs oh healthy!) I know the kind of things we come to beleive. This is not deprivation for the sake of deprivation, it is about health but it is a fine line.

        Please do a little more research on the difference between intermittent fasting and eating disorders.

        Michelle wrote on February 21st, 2012
  7. I’ve fasted for 24 hours on water only. I do feel better. Monday night to wednesday morning may be difficult. An easier 24 hr. fast would be to quit eating on say Saturday 2:00pm and eat again 24 hours later Sunday at 2:00pm. It seems easier, anyway.

    Crystal wrote on August 9th, 2007
  8. Hi Mark

    Inspired by Art Devany, I’ve been doing IF for a while now – combined with a low carb / paleo approach – and find it is realtively easy to stick to. I’ve leaned out a little bit from it and it actually frees up time from food prep.

    Eades wrote about this earlier int he year on his blog too.

    The method I use is typically to eat only in the evenings – like the Warrior diet or It is realtively easy to eat nothing during the day and feast at night. Loren Cordain had an article on this in his paleo newsletter a while ago

    saying that the evidence suggested that typically hunter gatherers would tend to eat big once a day. Which is sensible when you think about it – life was feast and famine in general and this approach mimics the same hormone drives.

    IF you search pubmed for “intermittent fasting” there are loads of interestig articles. There are a few on my blog too.

    Chris wrote on August 10th, 2007
    • How does that affect your workouts? Do you exercise in the morning on an empty stomach?

      Gracielou987 wrote on April 12th, 2011
      • I don’t know loads about IF, but I’m curious enough I may try skipping breakfast. I did, however, used to run in the mornings before breakfast. I was a bit more into mileage back then than I am now, I can remember going for 6-8 miles before breakfast. Seeing as primal workouts are less demanding on glycogen stores, I can’t see it taking that big of an effect.

        James wrote on May 22nd, 2011
      • Lot of people do this, Chris:

        – fast from 6 pm till noon (your body will do a cleansing during this time, and start cleaning out old broken cells)
        – exercise vigorously at 11 a.m. or 11:30 a.m. (right before you break the fast)
        – then have a big healthy meal at noon, right after exercising (it needs to be within a half hour) (your body will use the nutrients to rebuild, repair and rejuvenate)

        If you do it this way it’s important not to eat anything before you exercise, but eat very healthy foods (lots of healthy fats, carbs and protein) right after exercising.

        sarah Morrow wrote on July 15th, 2011
        • How often do you recommend doing this? daily?

          Mary wrote on April 5th, 2012
  9. I read it too fast and thought it said Intermittent FLASHING. Keep’in cool in the summer!

    Seriously, as I initiate a dramatic change in lifestyle to a Primal Diet, I have attempted to IF in the evening and it is too difficult at this time because of the already drastic reduction in caloric intake.

    However, I am able to sustain on a High Protein Shake (Meal Replacement) at 5:20 AM until a 12:00PM lunch weekdays.

    Honestly, I am not ready for any food consumption that early in the day. Shake and DCMF for breakfast.

    Oxybeles wrote on August 10th, 2007
  10. While I think that intermittent fasting is reasonable within the context of how we evolved and life prior to farming, I do have one caution. If you are susceptable to gout you may not want to fast or try it in short bursts and build up to longer ones. I’ve had a gout attack flare up practically every time I’ve tried this (voluntarily or not). Fasting tends to increase uric acid levels and increase your risk of having an acute attack. That said, losing weight will significantly lower your risk for getting gout so I am working on lowering my weight and taking the med’s necessary to stave off an attack at the same time.

    Brian wrote on August 10th, 2007
  11. I was doing a shortened eating window like Mike OD up there (MOD, is that you?), but was having trouble getting in enough calories in a 4 hour window. I’ve since switched to a 24-on, 24-off plan and I’m enjoying it. I don’t have to gorge as much to get enough food, I don’t have to feel overstuffed, and I can maintain my bodyweight and activity. I’m doing 6:30pm to 6:30pm of fasting and then 6:30pm to 6:30pm of eating, usually four meals (dinner, breakfast, lunch, light dinner).

    Scott Kustes
    Modern Forager

    Scott Kustes wrote on August 10th, 2007
  12. Michael Eades had some great write-ups on IF’ing earlier this year. I’ve been doing low-carbing (which had already become second nature) with 18/6 IF’ing since then. All you have to do is skip dinner or breakfast most days (no snacking!), which is pretty easy if you’re working.

    Terry wrote on August 10th, 2007
    • I definitely agree with this. Sometimes I’ll keep lunch too but I don’t make it a job. I just about always keep breakfast, I’m use to it now. But I decide at the time if I was to keep lunch, if I feel like eating, I eat. I just don’t make it a job or chore. Stress free as possible. I’m doing this in combination with the starch solution and it’s doing wonders for me already. I have been doing the starch solution for the last month and added IF for the last three days. My knees have been aching for at least the last two years. It’s gone! as inflammation in my arms has decreased to hardly noticeable and this is from hardly being able to move it on some days. I thank god for wisdom. Give up the meat and dairy people!

      Kenny wrote on June 4th, 2013
  13. My feet hurt!

    kim wrote on August 10th, 2007
    • hahaha

      brian wrote on February 3rd, 2011
  14. I like what’s called low carb in this context. I’m referring to an earlier post where Mark describes a lunch salad. I like eating this way. I don’t know if I have my food/energy level dialed in or if I’m just more naturally aware I’m in need of a nap (no constant supply of energy coming in). Anyway, the post has inspired me to fast, today. I’ve done it irregularly (which is the right way I hear) from reading Devany’s blog.

    What kind of exercise are people considering on fasting days? Mimic the ancestor and walk a lot like I’m in search of food? Maybe an occasional run and throw a rock like I’m aiming for small tree rodents?

    I normally do 3 exercises (from a mix of about 30) at high intensity 2 to 5 days in a given week. I’m skipping that stuff today.

    Abraham Williams wrote on August 10th, 2007
  15. After reading about this last Fall, I started doing IF, and have continued to do it with good results. I generally eat from about 6pm to 10pm at night and fast the test of the time. It is a good weight-management tool. After loosing some weight initially, I’ve stayed pretty steady for the last 5 months. This of course is without making any concerted effort to lose, but it sure is nice to not have to worry about how much I eat or even what I eat, as long as most days I eat what I feel is an optimal diet for me healthwise. So I wouldn’t say there’s no plateau for IF’ers. I think there are plateau’s for just about any eating plan. But I also think IF makes it very hard to regain weight and also potentially has some great health benefits on top of it’s facility in helping one lose weight.

    Levi Wallach wrote on August 11th, 2007
  16. It was nice reading the posts. I have started this way of eating two months ago and have noticed incredible results. Mostly, I fast for 19 hours and eat in a 5 hour window. I have lost weight and inches, have more (lots more) energy, sleep better and seem more alert. Generally, I eat whatever I want to in my eating window, but since the weight loss has slowed down, I am considering making some modifications and lowering my carbs. A couple things I noticed–the flavors of all foods seem more intense, so be prepared for fruits to seem too sweet, and be careful to taste your food before adding salt.

    You asked about exercise…well I will be 69 tomorrow, work full time and exercise 5 times a week. I do yoga 3 x and work out at a gym with a private trainer 2 x. I do all of the exercising in my fasting mode and have had only one time that I dot dizzy when going from lying down to standing quickly. That may have been due to dehydration, so I try to keep my fluids up during the exercise phase.

    Looking forward to learning as much as I can about this way of eating.


    MJ wrote on August 11th, 2007
    • Hello, I was wondering at time is your 4 hour window


      Joe wrote on March 30th, 2011
    • I’d like to add that this is what I do as well. I fast 7 days a week, eating only between 6-10pm, it’s not constant eating but I will have dinner, then maybe a little dessert and a glass of red wine all within this time frame, then I don’t have anything but black coffee till my next day.

      Every morning I get in an hour of cardio; uphill speed walking or a moderate jog. Then I do some weights all on an empty stomach. I feel wonderful living this way.

      I sleep better, I am mentally more clear and focused and after years of trying to find a eating plan that worked for me I can say I finally feel this is right.

      I’m 34 yrs, 5’3″ mother of 1, and weigh 112lbs…down from 178 3yrs after having my son!

      Farrah Knight wrote on May 24th, 2012
      • Sorry but this sounds extreme. The reduced eating, the hour of daily cardio etc on an empty stomach EVERY DAY…. and your weight is ok now, you can find a somewhat more moderate lifestyle plan now.

        cis wrote on July 11th, 2013
  17. This IF stuff is becoming quite a fad in the fitness world today. As interesting (and seemingly logical) as this article was, it lacks solid research to validate some of its claims. Much ‘promising’ research has only been done on animals. Take a look at this for more info:

    Moe wrote on August 12th, 2007
  18. PS… Don’t get dragged in by weight loss anecdotes! Many people will experience weight loss simply because they are NOT eating as much as they used to, because, well, their available eating times are significantly reduced.

    Moe wrote on August 12th, 2007
    • Moe, do not downplay practical experience. Anecdotal evidence has its place in these types of issues where sufficient scientific evidence has not yet been completed.

      Patrick wrote on February 2nd, 2011
      • Or you could just try it for yourself and experience the benefits first hand! Placebo or not you’ll look and feel better.

        Wylie wrote on April 13th, 2012
        • I don’t feel better doing 2 IF days a week (dinner previous day to dinner today), have lost NO weight or body fat whatsoever (in fact, I seem to have put some weight on and body fat seems to have increased!). During fasting, I got some headaches and have low energy issues: not so much physically but rather I feel unable to do any mental work (even invoicing or playing sudoku feels difficult, let alone creative thinking about where to take my business or contacting clients). Also, I am a fitness instructor, so I am expected to be active, energetic and in a good mood (not grumpy from lack of food) daily.

          I do enjoy being able to have a nap in the afternoon between classes, but overall I suspect this approach is best suited to men than women.

          cis wrote on July 11th, 2013
  19. Have many of you tried the Master Cleanser by Stanley Burroughs. Its the one done by Beyonce with the Madal Bal Syrup. I am actually the US distributor of the syrup and thought some of you might be interested. The Master Cleanse makes fasting a bit easier than juice fasting because you get more calories from the syrup yet you still give your digestive system a rest. Over the years working with this diet I have heard so many miraculous stories that I really believe periodic fasting is the missing link in western medicine.
    Be well,
    Charlie Rebich

    Charlie Rebich wrote on August 15th, 2007
  20. Hi,
    I have been doing intermittent fasting (eating every other day) since January of 2007. I only use water on my days off food. Many people I explain this to say it sounds to difficult for them. However I found the body adapts and gets use to the routine, you have to stick with it or it becomes difficult. That is the only trick to it, just maintain the routine and you won’t be hungry on the days off, but if you cheat and make exceptions your system gets confused and you will have trouble. When people ask why your not eating today, just say you are detoxifying today(which is true), don’t say fasting or they may start to judge you because they may not understand etc. I’m also now a 100% vegetarian with I am enjoying very much and have never felt better in my life. I also completed a long fast (healing) in January for 14 days (water only) this was more difficult and I don’t recommend anyone to do this without a lot of knowledge on it first and even medical advice from a Doctor who knows the subject. I plan on a 30-40 day fast (water only) when I’m ready. The intermittent fasting will always be part of my life and I just would not be happy going back to eating food every day. If you have any questions I checked the notification for resposnes to this post. God Bless!

    Jordan O'Hara wrote on September 7th, 2007
    • “I plan on a 30-40 day fast (water only) when I’m ready. ”

      I really hope you’re not serious, because this is a recipe for serious health problems up to and including organ failure, hair loss, severe weight loss, and even death…

      George wrote on February 25th, 2010
      • Many people complete 30-40 day water fast all the time. However, for the unexperienced faster you would want to be under medical supervison as you have to monitor the body carefully. For the experienced faster you will know already if you can undertake a 30
        -40 day water fast. Also you would want to ‘fast prep’ meaning living a ‘very’ healthty lifestyle for as much time as it takes to be in excellent health – otherwise the toxins released during 30-40 days could cause complications. I’ve completed 5 – 15 day water fast with no supervision and no trouble and will complete a 30 – 40 day water fast when I know I’m ready for the journey.
        There is over 100 years of medical data showing the safety of water fasting.

        Jordan O'Hara wrote on February 25th, 2010
        • You posted this in January so you’re probably dead by now, but if you’re still in the process of “prepping”, please don’t starve yourself for 40 days. You will die. You’re a lunatic.

          Joe wrote on November 14th, 2010
        • I’ve never starved myself and your generalization that fasting for 40 days causes starvation is incorrect. A complex organism in a true fasting mode has no direct biological relation to the state of starvation…starvation only occurs when all the bodies reserves are depleted and you start converting energy from the vital organs. A person in starvation mode would be hard to miss – skin would be tightly wrapped around all the bones and they would look like they should be dead. I’ve been fasting periodically for many years so my body is well adapted for this lifestyle. Anyone without years of experience should probably not attempt a 40 day water fast but rather stick to 15 days or less under medical supervision.
          Final note: Comparing fasting to starvation has been an error I have seen in some medical books – this is due to lack of knowledge on the subject and also often used as a scare tactic to keep the general masses from discovering the power of fasting. However, I do not see fasting becoming very popular as many people I find ‘live to eat’ instead of eating to live.

          Jordan O'Hara wrote on November 14th, 2010
        • i find it interesting how so much of this parallels the eating patters of an anorexic/bulimic.

          i should do, i am both.

          Ashleyy wrote on April 14th, 2011
        • According to Bragg, starvation does not occur in a 30-day fast. It is only if you fasted, over 40 days that you would incur starvation. He should know because he did lots of (distilled) water fasts and healed lots of people that way (and lived a long and healthy life). However, I simply cannot accept the highly ketonic state they cause – it makes me feel very sluggish and unwell.

          cis wrote on July 11th, 2013
        • Props to Jordan, who seems to really know what he/she is talking about. I’m curious as to whether you ended up taking on the 30-40 day fast, now that it’s October, 2013?

          Shannon wrote on October 11th, 2013
    • Hi Jordan,

      What do you find to be the benefits of alternate-day fasting?

      Jake wrote on May 6th, 2012
  21. Hi I was just wandering around looking for more information on fasting, I myself am on my 8th day of just water, I am feeling so much better, I havent cheated once and I started at 242lbs and now Im at 217lbs, the weight came off quick in the begining and now I loose about 1lbs a day, I am so pleased that I dont feel hungery I never thought I could even go 1 day without food. So to anyone that has doubts( You can do it!)

    Rose wrote on September 7th, 2007
    • Hi,

      I have done the master cleanser and lost about 40 pounds, How many days have you gone and how many have you lost. I am now a hardcore grok, so no fear in gaining the weight back after losing it.


      Peter wrote on March 21st, 2011
  22. IF may be good for your health but not for losing weight. As soon as you eat the next day you start gaining it back at least for me.

    Cheryl Diamond wrote on October 7th, 2007
    • One thing about water fasting is that it forces your body to use the energy stored to maintain activity. That’s its only choice, since no energy is entering the system.

      Because of this and the fact that fat is the body’s optimal source of energy, IF is excellent for decreasing BF levels. I certainly suggest that everyone try short fasts at first, as recommended in the comments previous to mine. Maybe 16-20 hours at first. Maybe one day out of the week. Something like that.

      As for you regaining some weight (did you mean fat or just BW?) after you stopped, it could just be water weight OR you were simply eating the wrong food.

      Another thing to keep in mind is that body weight fluctuates to some degree. If you gained weight the day after your fast ended, it could simply be because you had extra weight in you! The food!

      All the best,

      Patrick wrote on February 2nd, 2011
    • Cheryl, I agree. I also think this is more of a problem for women than for men. Men seem to do better on IF diets (also the “5:2 diet”) and similar. Women may need to keep a more balanced food intake (including enough good fat) for hormonal balance, for instance.

      cis wrote on July 11th, 2013
  23. well it has now been a little over a month and as I said I started at 242lbs and now Im at 192lbs. I have now started eating a little veggi broth and every other day a mashed up veggi like a carrot, I mash it so it digests faster and easyer, for me this whole thing has had to be a change that will be with me my whole life, you see my grandmother died at 700lbs, my mother is 450lbs and I have a younger brother that at 22 weights about 360lbs so my fasting has been to correct my eating habits and make the change that will keep me around longer for my 3 children, I cryed when my kids got excited that they could give me a hug and fit their little arm’s around me all the way, I feel great inside and out, I will never make excuses again!

    Rose wrote on October 8th, 2007
    • I know this was 3 years ago.. but reading this comment made me want to cry (happiness and hope)! I hope you’re still strong!

      SarahAnn wrote on February 11th, 2010
      • I’m real inspired at this post. In my 20’s I IF’d after two childbirths and lost about 75 pounds after each child. I kept it off until age 35 when my job and a divorce got too stressful. Then at 40 I was disabled and jumped to 235 pounds with hypothyroidism. I fasted off 35 pounds three years ago. Then got into cycling and lost to 187. Then injured a knee for a year and up to 216. Last week decided to IF like when I was in my 20’s. I mainly fast and only eat a full large meal every 48 hours. I’m on blood pressure meds with a diuretic so on fasting nights I have bullion so I don’t get sick from the blood pressure medicine. I spice it up with jalapeno, fresh basil, chinese 5 spice, onion and it feels like a meal! If my stomach hurts I might have 4 crackers or a cup of soymilk right before bedtime and take calcium, vit D and magnesium. I am on calcium and D per my doctor for deficiency. I do this for 5 days then eat for two days. I just did my first week and went down a size. What I like about IF is freedom to eat foods I like again without guilt. I still eat mostly vegetarian but BBQ or ice cream doesn’t freak me out like it used to on occasion. I am prediabetic so I am hoping to lose 100 or so pounds in a year and reverse the diabetes and high cholesterol and not need blood pressure meds. I have to get my health back. Everyone nearly in my family is diabetic and I don’t want to be one. I’ve tried every diet in the world and IF is the only thing that works for me. I believed the media on low fat etc and I ended up fat again listening to the media and the government/ food industry hype. Never again! I IF’d from age 18 to 30 doing it two days a week for maintenance. I was in perfect health and slim. I **will** do it again. Also to Mary Titus. Watch the fats. The liver will turn it to glycogen and it becomes sugar in the blood on your morning fasting glucose meter. Fat is ok small amounts.The liver turns any food group into sugar as needed. Carbs spike glucose right away whereas fat becomes blood glucose 8 hrs later.

        Linda wrote on May 2nd, 2010
        • Soymilk? I hope you realize soybeans cause so many problems from reproductive organ disorders to hypothyroidism to brain shrinkage that they are basically well-marketed toxins, right?

          mm wrote on December 19th, 2010
    • Wow…that is amazing weight loss!!!! Did you notice having a lot of loose skin after losing so much weight so quickly? I enjoy fasting but never wanted to lose more than 10 lbs at a time so skin can catch up!!

      Mariann Sidor wrote on May 15th, 2012
  24. I have being on a 20-hour daily fast since 04-01-07 and the result has being amazing.Prior to this fast ,i was lethargic,having chest pains,weighing 83kg(height 5ft 4inches),depressed.presently i am weighing 65kg which i have maintained for past 6 months.I have never experienced so much energy and happiness in my life.I am focused and rearing to go.I eat as much i like after 6pm daily and stop eating at 10pm.i have not being sick since i started this program.I hope this helps someone

    atumu wrote on November 23rd, 2007
  25. Yeah same here atumu I have been doing 20-hour daily fasts on water for nearly 2 years I dunno if its working but I am about 54kg 5’7. I eat as much as I want anytime really. Sometimes I start at 8pm, sometimes I start at 5 – 5:30pm. But no earlier than 4:30PM. When its cold and rainy and I have got nothin to do in the evening I just start whenever.

    Mitchell wrote on February 5th, 2008
  26. One meal every second day would be the best lifestyle for humans-(super). The meal should be of the highest possible nutrition such as oranges and apples and only small amounts eaten over a few hours. If one absolutely feels they need more calories then adding juicing to the meal would work. But remember the trick is to provide only what the body needs nothing more and nothing less. All cells in their natural state are immortal until debris is introduced (caused by eating) which leads to cellular death-(aging). Since humans have no other method of cellular stimulation – (needed to live) besides eating we are stuck with eventual death. To reduce the speed of cellular death we need to eat only what is required for stimulation allowing human life using food types that have built in cellular protective characteristics such as anti-oxidants.

    Jordan O'Hara wrote on March 17th, 2008
    • Boy I don’t know about just eating apples and oranges cause you would be a twig literally starving wouldn’t you? If you have NO protein you have NO muscle. Which means you can pump all the iron you want and its not gonna do anything if you can even still lift it. Won’t your body start eating your muscles?? Can’t you do a water fast like two to three days a week then on the other days eat 4 to 6 meals with lots of protein, complex carbs like red and sweet patatoes and veggies?? What do you all think?? Lose fat, still build muscle?

      Jeff wrote on September 5th, 2009
    • Interesting. Too intense for me, but I do a cleansing fast ever quarter. Stanley Burrough’s Lemonade Clease. I love that for 10 days or more. It renews my resolve to stay healthy. I started at 317 lbs now I am 227 lbs. Not sure of a weight goal, just a how I feel and look goal. These stories though encourage me. I commend anyone who sticks to what they believe in.

      Tanya wrote on December 5th, 2010
      • Actually Master Cleanse. It’s a whole lifestyle change. Eating veg. after a 10-60 day cleanse. Small amounts of fish organic only. I don’t striclty adhere, but I do get as much organic food as possible. I still do pork and beef a few of times a year.

        Tanya wrote on December 5th, 2010
    • Correct, absolutely correct. Young
      children and adolescents need at least
      3 meals a day. Young adults to age 30
      probably only two. From age 30 or 35
      to age about 50 one meal a day is
      ideal and beyond age 50 only
      one meal every two days. I currently eat
      only once every two days. The single meal should include all food groups and, (unless you are trying to lose weight), enough
      calories to keep the weight stable. Absolutely the worse diet you can have
      is ‘grazing’; this overworks the Beta
      cells in the pancreas (these produce insulin) and continuous eating is the major cause of the rise in maturity onset diabetes and obesity in our
      society. The human body has evolved to
      not only tolerate episodes of fasting
      but this is the NORMAL metabolic state.
      During fasting insulin drops and the
      pancreas releases glucagon. Glucagon
      raises the blood sugar and tells the heart to stop burning sugar and start burning fat; the heart is an obligate
      fat burning organ but only burns fat
      when the glucagon is switched on
      (i.e., only during fasting). The heart is the only obligate fat burning organ in the body. Dominance of glucagon metabolism over insulin (in terms of time) slows down the aging process, raises the good lipoproteins and slows down the rate of vascular atheroma development. Hence it lowers the risk of
      stroke and heart attacks (smoking is a much bigger risk factor however; so stop smoking before you even think about doing any fasting). It also reduces the blood pressure. It takes getting used to but, believe me,
      it’s actually easy once you become accustomed to eating every second day
      only. (N.B. I regularly swim 3 kilometers before I eat my meal, having
      not eaten for at least 36 hours – no problem at all).
      Hope this helps people.

      Greg wrote on December 31st, 2010
      • greg, I love your type of knowledge, can you recomend books, or sources where an exposition of your thoughts can be found?

        mory wrote on May 27th, 2011
  27. Why does everyone choose to do an eating window
    at night? I much prefer to do breakfast thru
    lunch and then fast for the rest of the day.
    It just makes more sense to me. I have only been
    trying it a few weeks just to loose some additional fat to increase my running speed. In the past the easiest way to loose weight was to
    concentrate on limiting my evening meals. It also
    frees up more time for you to do other things…
    like the exercise of your choice.

    G man wrote on April 1st, 2008
    • I prefer the evening window because it allows me to have dinner with my family. I struggle with not eating in the evening when I have to cook and the rest of the family gets to sit down and enjoy it. I’d rather not eat while I am at work. I use my breaks to read my favorite books or magazines instead of eating then enjoy dinner with the ones I love. :)

      MrsBehaving wrote on December 13th, 2010
    • Not everyone is the same. What works for you may not be ideal for others. For some people it may be easier to sleep through the first 6 to 8 hours of their fast. what better time to be hungry than when you’re asleep?

      Faster4life wrote on April 9th, 2011
    • I do so in the evening simply because I’m not hungry in the morning. I’m at 84 kilograms, by the way. My healthy weight range is from 60 to 80, so I’m aiming for the happy medium of 70. Last Sunday, I started doubting the often repeated advice that breakfast was necessary for weight loss, and I stopped eating breakfast, starting my day with just water. At my age, 43, I don’t think I even need lunch. The usual mantra is that you’ll eat an entire warehouse full of food in the six hours a day that you’re not fasting. Ha! I’m eating the same amount at every meal as I normally do.

      Lucky Joestar wrote on November 29th, 2011
  28. I like your concepts, Jordan. You would become
    really lean and effecient on that type of diet.
    Getting going on it would be an adjustment though…

    G man wrote on April 1st, 2008
  29. Regarding the eating window. My theory behind eating a super only instead of breakfast or lunch is this: Digestion takes allot of nerve energy, if you eat breakfast and lunch the body is busy assimilating food all day. If you avoid eating breakfast and lunch, you instead detoxify all day (repairing) and you have all that extra nerve energy to use on what-ever you want…work etc. Some of the Free E-Books on my website discuss the NO breakfast approach to health.

    Jordan O'Hara wrote on April 1st, 2008
    • I love my breakfast… I feel hungry in the morning (within 1 hour of being awake) and it is hard not to eat then. If I don’t eat (ignore tummy noises) because of time-pressure or as an experiment, I then start feeling weak by lunchtime and weak/grumpy/hating life by 2pm. My diet is fresh foods, mostly veggies, some fish, fruit and nuts/seeds, no dairy, no grains.

      cis wrote on July 11th, 2013
  30. Jordan,

    Now I understand…you mean supper instead of
    super, right? I thought at first you were saying
    that eating once every other day would make you
    a super human.

    G man wrote on April 1st, 2008
  31. Woops! Sorry about the typo. Yes I mean Supper (Evening meal).

    Jordan O'Hara wrote on April 1st, 2008
  32. Mark,

    I think you might have to do a more clarifying post. I don’t think IF is meant to be long periods of starvation, and it seems some of the people responding think that is what you mean. People SHOULD eat, but there are benefits to intermittently not eating. I’d love to hear more about what are acceptable intervals and what is just plain starvation.

    camille wrote on April 15th, 2008
  33. First I should mention that fasting and starvation are two different things completely. During fasting the body uses Ketones for energy built primarily from fat reserves. During this time the body cleans house…removes any debris and attempts to rebuild any damages that it finds. Starvation only starts after all possible Fat and lastly muscle reserves have been depleted-basically you would look like a walking skeleton with some skin on it before you begin to starve. This takes many months to start for the average size human.

    Starvation with an IF lifestyle is impossible in my opinion. IF generally includes eating one day and fasting the other. I practice this lifestyle. I take in vegetables and fruits in liquid form every second day – no solids. I then Dry Fast (no water – no food) the other day for about 36 hours. (Dry fasting only recommend for experienced fasters) In total I go for over half the year without food or water, additionally I do at least two 15 Day water fasts. I maintain a weight of 190 pounds and I am very physically active. If fasting every 2nd day is too difficult then even 1 day a week would be very beneficial to the body and mind. For anyone truly serious about adopting a lifestyle involving fasting then you may wish to visit This site has fasting MD’s who are very experienced with supervising fasting. It was a great help to me when I was just starting a transition to this lifestyle. Remember… we are not nourished by the amount of food we consume but rather by the amount we assimilate.

    Jordan O'Hara wrote on April 15th, 2008
  34. I can offer a comment to G’s question about why some of us choose the evening as the eating window. I used eat only during the day but it often proved challenging to refrain from eating at night if hubby was cooking something that smelled fantastic. Not to mention air popped popcorn (one of my weaknesses). As a result I was sure I consumed more calories than I was aiming for.

    Since reading this website and trying the reverse – black coffee between 9 and 10, water with lemon all day and breaking my fast with fruit, then easing into a big salad, protein and steamed veggies at night. I have had postive results overall.

    In addition, eating at night will allow me to fulfill all my social engagements without having to be so fearful of eating. I am definitely less food obsessed and look forward to eating rather than having it be all about weighing my food and trying to figure out how many calories etc.

    I use the 3 days on, 1 day off schedule promoted over at and do a run with some intervals followed by a cf workout.

    Thanks so much for this website, Mark!

    Monica wrote on July 18th, 2008
  35. I have really enjoyed reading all of these very informative posts. I found my way to IF through a diet called The Doctor Johnson’s Up Day Down Day Diet. He suggests eating no more than 500 cals one day, then eat to satisfaction the next. But he had also talked about intermittent fasting, but said that “most” people could not do that, so their goal was to stay under 500 cals. But being the hard headed person I am, I was determined to not be “most” people. I have been fasting every other day for 2 weeks now, and find my fasting days much more pleasurable, than my eating days. I have more energy, better mood, and all around improved perspective on eating, and my relationship with food. I enjoy my ability to eat more intuitively now. I will be following this way of eating the remainder of my life!

    Jackie wrote on July 23rd, 2008
    • This page hasn’t been active for a while, it seems, but still a wealth of information and sharing. After an accident resulting in severe hip injury, I was extra-motivated to lose weight. At 40, I was about 75 pounds over. Factors such as difficulty exercising due to pain and reduced mobility, plus a change in my living situation, led me to what seemed an easy and natural solution: I just stopped eating alone. Sometimes I would eat one or two meals every day, sometimes I would go up to 4 or 5 days fasting. When I do eat, I eat whatever I want. And this ”whatever” has changed, as now I only want to eat healthy foods. I have done up to 15 days water fasting in the past, and find it easy. I’ve lost over 50 pounds in the past 7 months. During periods when I eat ”normally”, I don’t gain weight, but maintain. This is working for me. It’s easy, both physically and psychologically. For most of human history, eating has been a collective activity.

      Anna wrote on January 19th, 2012

Leave a Reply

If you'd like to add an avatar to all of your comments click here!

© 2016 Mark's Daily Apple

Subscribe to the Newsletter and Get a Free Copy
of Mark Sisson's Fitness eBook and more!