Dear Mark: Feast or Famine Diet?

Among the questions I get from MDA readers are those that ask about timely diet trends – you know, the latest regimens highlighted in the media or promoted by high profile stars and athletes. Some are bookstore blockbuster plans like The Zone, while others are the latest celebrity diet du jour. As my wife and – well, everyone who knows me – can tell you, I’m always up for talking, debating, deconstructing, and fully dissecting any version or concept of diet under the sun. (Thankfully, my wife at least finds it endearing after all these years.) But it’s a treat when a diet trend comes up I can actually find common ground with. Take this question from reader Jim.

Dear Mark,

I saw something this week about a “feast or famine” diet. From what I get, people alternate eating a small amount and eating as much as they want. I’m still kind of a newbie and wondered what you thought of it. Thanks! Love the PB!

The feast or famine diet (also called alternate day fasting) isn’t really a new idea (even discounting Grok’s experience), but it got recent press after the American Journal of Clinical Nutrition published results of a small study this fall. Researchers at the University of Illinois Chicago designed an alternate day regimen that restricted food on “famine” days to 25% of estimated energy needs. Sixteen obese participants went through a 10-week program: a 2-week control period, 4-week alternating day 25%/”controlled intake” period, and 4-week alternating day 25%/”self-selected intake” (albeit with diet counseling) period. The results? (Can you guess, IFers?) Subjects lost weight consistently in both 4 week periods and showed improvement in key blood markers (total cholesterol, LDL, triglycerides and systolic blood pressure).

A few years ago a neuroscientist named Mark Mattson published study results supporting the same famine-feast regimen. In commentary for The Lancet, he questioned the conventional wisdom that supported “grazing” for calories throughout the day, citing humans’ evolutionary development within an intermittent fasting existence. Mattson, a central researcher in calorie restriction and intermittent fasting, has produced research demonstrating the benefits of both practices, benefits which include enhanced memory, reduction in neurological oxidative stress (with associated risk of neurological conditions like Parkinson’s and Alzheimer’s), neuron resilience, and an improved regulation of glucose and insulin levels.

As an intermittent fasting routine, the feast-famine diet promises to upregulate metabolic systems while decreasing the overall caloric intake and oxidative stress associated with food intake and digestion. In the Primal Blueprint model, I highly recommend it. As Mattson and other researchers have noted, our systems evolved to expect periods of scarcity. We weren’t designed for the constant eating (and associated physiological stress), couched as healthy “grazing,” that we’re told to practice today. Dr. William Davis of the Heart Scan Blog, a blogroll friend of mine, did a great sequence a few weeks ago on grazing, fasting and postprandial patterns. As he emphasizes, the postprandial (aka “after eating”) period is the most damaging for artery plaque buildup. In our society, we’re encouraged to be starting the next meal before the previous one has even been fully absorbed. Our systems rarely, if ever, have the chance to return to zero. Fasting allows for that resetting.

The common criticisms of the feast or famine routine (or any form of fasting) revolve around images of all-out gorging. Apparently, too many experts believe that anyone who fasts for even 24 hours will be found in a gluttonous mountain of pizza boxes and Snickers wrappers at the end of restriction time. There are people who might go this route, but I’ll bet you a nickel they won’t continue the alternating day routine. The practice takes a certain amount of discipline, yes. But it also takes energy. Gorging yourself on the worst foods will leave you so sluggish and miserable the next day that you’ll likely drop the program. That said, if you return to a diet (say, the PB) that keeps your glucose and insulin pretty steady, you’ll feel the best benefits of the fasting routine (lightness, focus, energy) instead of the carb hangover.

Finally, I want to stress that if you’re interested in the benefits of a feast-famine routine, you don’t need to commit to an alternating day diet. Nearly any form or degree of intermittent fasting provides benefit. Do what feels manageable in the beginning. Skip breakfast one day. Reduce your calories by half for a day. Every IFer I know (myself included) developed – and advanced – their routines over time and manage it with ease now.

As always, thanks for your questions and comments, and keep ‘em coming!

About the Author

Mark Sisson is the founder of Mark’s Daily Apple, godfather to the Primal food and lifestyle movement, and the New York Times bestselling author of The Keto Reset Diet. His latest book is Keto for Life, where he discusses how he combines the keto diet with a Primal lifestyle for optimal health and longevity. Mark is the author of numerous other books as well, including The Primal Blueprint, which was credited with turbocharging the growth of the primal/paleo movement back in 2009. After spending three decades researching and educating folks on why food is the key component to achieving and maintaining optimal wellness, Mark launched Primal Kitchen, a real-food company that creates Primal/paleo, keto, and Whole30-friendly kitchen staples.

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60 thoughts on “Dear Mark: Feast or Famine Diet?”

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  1. That’s really very interesting. I know from having done a couple of 24 hour IFs and then doing 17 hour fasts by just missing breakfast, that it really does make me feel more alert, more productive and just more alive.

    It’s good to get some more evidence that doing something that feels good is also actually a beneficial thing to do.

  2. I can see my next experiment looming on the horizon…

    I tried IF a while back, but it was before I had my Primal ways down, and it didn’t go so well. I’ve seen advice since to get your food quality dialed in for a while first before trying IF, because it’ll go a lot easier.

    Now that I’m eating 95% Primal, it seems that it’s a good time to look more into this.

  3. Feast Famine?

    It’s hard to believe, but I do some form of IF everyday. I tend to eat one big meal during the day or in the evening (whatever’s convenient) and just cruise the rest of the 24 hrs.

    It’s incredible once you realize you only have to eat once; One meal means more time!

    1. Not hard for me to believe 🙂 Pretty easy actually, especially if you can keep yourself busy.

      I’ve been a grazer since Thanksgiving corrupted me, but I usually do the one meal deal. About the only way to keep my daily calorie intake from from grasping at 5 digits.

  4. All of this info is so new and cool to me. I’m impatiently awaiting my copy of Primal Blueprint to hit my mailbox this week. Perhaps in honor of its arrival I’ll fast till it comes… Or smoke a pack of Marlboro 6-packs…

  5. I have been doing this for about a year. I found it as JUDDD (Dr. Johnson’s alternate-day dieting) when I was stalled for a long, long time and unable to lose weight. Since I’m both post-menopausal and hypothyroid, I have to severely restrict calories, but that’s difficult on a daily basis. This program has been great. I don’t do true alternation (for convenience), but I do 350 cal on M, W, F. On Sat or Sunday to ‘balance’ things, I’ll do a ‘medium day” of about 1000 cal. The other days aren’t a gorging thing–I eat to satiety but primally and moderately.

  6. Intermittant Fasting is one of the most interesting fitness/weight loss niches.

    There are people who swear by this method and others who think it is the stupidest idea they have ever heard of.

    Unfortunately, most of the people who think that it’s a bad idea have never even tried it.

    Personally, I questioned it’s effectiveness for most “normal” people due to the likelihood of a post fast pig out on ice cream, candy, pizza ,etc…

    In an attempt to test that hypothesis, I had half a dozen of my clients test drive two different IF programs.

    Three of my guinea pigs tested an IF after a week a healthy, paleo style eating.

    The other three testees tested an IF after a week of typical North American eating.

    The paleo group found that during the IF:
    Their energy levels were unchanged
    Their hunger was under control
    Their athletic performance was fine during moderate intensity exercise, but was a bit of a problem during high intensity
    and they didn’t pig out after breaking the fast

    Conversely, the typical N.Am diet participants

    Were ravenous throughout the IF
    Had very low energy levels
    Craved carbs like it was heroin
    and pigged out for hours after breaking the fast

    The paleo group lost a little weight – too small to notice difference between fat & water weight, while the N.Am group gained weight.

    My conclusion:

    IF is a useful tool for trainees who already eat healthy.

    I wouldn’t recommend it for the average Joe

  7. Douglas, that is amazing! Wow is all I have to say.

    Lately I haven’t felt the need to eat breakfast, so I haven’t. Yesterday I went for a longer period of time with no eating because the day before I had more carbs than I was used to. I ended up eating in the evening with bacon and sweet potatoes (cooked in the bacon grease).

    What I want to know, if anyone has done any experiments or has experience is if it is better to IF after a day of eating non-primal, i.e. if you’re at a friends house and the only non primal thing they have is steamed broccoli or a holiday dinner with family.

    1. I’ve found that it’s “better” to just not have a non-primal day if you can avoid it. But sometimes if I do (hard to be perfect you know) fasting is one way to “reset” things, especially the carb cravings.

      Otherwise I might have a few really high carb days in a row (even if they’re primal carbs like fruit). It’s not the end of the world, but … having a meat/eggs/cheese only day or IFing for 18-24 hours really does help me get off the carb cravings after a “slip up.”

  8. kongluirong

    I don’t know if “better” is the right word.

    My experience is that IF is easier when you are already eating healthy.

    After a big holiday feast, odds are that your resultant blood sugar/insulin levels are going to make an IF pretty miserable.

    You will be ravenous all day long.

    That’s my experience anyway

  9. Anyone care to comment on this?

    Cutting your calorie intake by more than 15 percent makes your brain think you’re starving, so it shuts down testosterone production to wait out the famine. “There’s no need to reproduce if you’re starving,” explains Thomas Incledon of Human Performance Specialists in Plantation, Fla. Ironically, this dive in circulating testosterone stops you from burning body fat efficiently, so you’re actually thwarting your hard efforts to melt that tire off your gut.

    1. There are data to back this up. But this drop in testosterone and suppression in metabolism doesn’t occur unless it is long-term continuous calorie reduction over a period of weeks. In IF or ADF, calories are not *continuously* reduced. Most studies show that fasting actually raises the metabolism and the levels of catecholamines forup to 72 hours. Which makes sense from an evolutionary perspective: You’re hungry? Then you better get on your feet and go hunting and gathering.

    2. Whey protein (no carb/fat) mixed with water two or three times a day constitutes my “fasting” days (35 grams protein per shake). I feel I get all of the benefit of a true fast without sacrificing hard-earned muscle or potentially diminishing T production.

      1. “all of the benefit of a true fast”

        Well not quite, for several reasons… but I’m a fan of the protein sparing fast with quality whey also. If you’re having a hard time for whatever reason on a water fast, a protein scoop is a nice way to compromise and still have great results 🙂

      2. Guys I would just like to say I TOTALLY disagree with this! It makes no evolutionary sense that if Grok didn’t have any food for a day or two his body would start chewing up all his hard earned muscle, the very muscle he needs to get his next meal! Not to mention water+whey (pure protein no fat no carbs) being totally unnatural in an evolutionary point of view… Im also pretty read up on these matters, and I have come across NO evidence whatsoever that this protein-sparing idea has any legs. If it does I would love to see some research! But to me it just smacks of old ‘grazing’ conventional wisdom…

        1. If you’re worried about losing because of IF, you don’t have much to worry about.

          Intermittent fasting raises HGH (human growth hormone) levels, which protects muscle and even encourages muscle growth. Also, probably the best way to ensure you keep your muscle would be to do some INTERVALS or do some HEAVY LIFTING on your IF day. Just make sure that you get a good amount of protein in your next meal.

          After all, the old saying truly does apply to muscle: If you don’t use it you lose it.

        2. I agree you don’t need it, and feel it’s more beneficial if you DON’T use it.

          For body composition reasons, the shakes can help get through tough fasts rather than say… scrapping the whole thing. They are low-cal and provide good amino acids. Many people don’t resistance train to preserve muscle during fasting, so it may not be a bad idea for them.

          Depending on the brand, one 30g shake scoop has almost the same macro nutrient content as Grok eating a small squirrel or chunk of rabbit 😉 Unless you have squirrels and rabbits living in your house like me, many people have better access to shakes. LOL

      3. Um, I run, mountain bike and weight train all pretty seriously. I find that if I don’t have at least a little protein each and every day my performance suffers (time and weight are absolute measures); just me sayin’ is all.

  10. In the Varady study mentioned about, the subjects lost as much weight in the second 4-week period as in the first, implying the potential “momentum” for continual weight loss beyond the completion of the study.

    I personally observed in friends and weight loss people I work with that IF and ADF are highly flexible and are incredibly compliant. I’ve been doing this for 3 years now, and I’m convinced that it can be a sustainable and permanent lifestyle.

  11. Actually, my experience has been the opposite. I’ve lost fat with this kind of fasting, and my midsection is leaner and way more defined than ever before. As a 6 ft., 183lb. man, my waist is about a 29 or 30. I must admit though, I eat pretty paleo as it is, with mostly meat (including seafood and eggs)and leafy greens.

    I do cheat occasionally. In fact, I cheated pretty much every day with sweets for the last two weeks due to the holiday offerings, and have found my physique has stayed pretty constant (after the initial bloat from the gluttony wore off). This was after doing IF all summer/fall.

  12. I was answering this post with my last post:

    Anyone care to comment on this?

    Cutting your calorie intake by more than 15 percent makes your brain think you’re starving, so it shuts down testosterone production to wait out the famine. “There’s no need to reproduce if you’re starving,” explains Thomas Incledon of Human Performance Specialists in Plantation, Fla. Ironically, this dive in circulating testosterone stops you from burning body fat efficiently, so you’re actually thwarting your hard efforts to melt that tire off your gut.”

  13. Do you recommend the (IF)if you are training in a high intensity workout regiment (Crossfit)? I’ve found that the grazing is the only possible way I can get in the neighborhood of the amount of protein required to maintain muscle growth.

      1. Going by Mark’s recommendations I try to consume a gram of protein for pound of body weight. Approximately 200 grams per day.

  14. Not to mention the fact that an IF will cause a decrease in the production and absorbtion of testosterone.

    1. The decrease in absorption and production of testosterone would be after hunger for well more than 72 hours to the order of weeks. Unfortunately people have allowed semantics to cloud the issue.

      When we are hungry we say we are starving because we feel ravenous. In reality this is just somatic hunger which has little to do with our actual needs, just a time conditioned digestive tract trigger. The real hunger is limbic, real hunger effects energy production and has real noticeable physical costs other than grumbling stomachs (which are meant to be a conditioning response to make you eat.) Note that stomach grumbling vanishes within 2 to 30 minutes and will not return for hours sometimes (till your next conditioned eating window).

      Now I mention this because medically, starvation is what you found in the survivors of Auschwitz. Their bodies were literally feeding on themselves. Starvation is what you see in those pictures and videos of famine in Africa. Starvation is what you see in a long term anorexics. This often requires weeks and months to achieve. When starvation is reached, everything that is said about “famine mode” is true. In real terms your metabolism will not slow down until you have gone approximately 72 hours without food. Intermittent fasting is at most 24 hours (though I’ve heard of 48 hours periodically).

      If you are doing intense work then you will need a few more carbs than usual. Remember that the fasting depletes some of the natural dangers of carb overload (just don’t gorge), but it also depletes the muscle. as my trainer proved to me one day. If you haven’t eaten in 24 hours and your workout is suffering… it’s all in your head, and you need to stop making excuses to yourself. Evolutionarily speaking, it makes little to no sense for the body to slow down in the early part of hunger or even famine. it needs to speed up because, that is when you need the most energy, most desperately to hunt.

      Another approach is the eat stop eat approach which is just 2 24 hour fasts a week. You won’t even notice those and can plan your workouts around the other 4 days you are eating if you feel you cannot bring it on a fast day.

      When you come out of a fast, eat a regular meal, don’t eat a whole day’s supply of food. That is a pointless exercise.

      1. That’s a very good point…

        I’ve never read an article that clearly defined the time that had elapsed in the fasting mode to yield the production and absorption of testosterone.

        What do you mean 2 x 24hrs fasts per week? That seems like a lot of fasting. I thought intermittent would literally be a sporatic fast over a given time period.

        1. The most popular intermittent fasting program online is Eat Stop Eat. In it he advocates a 2 X 24 hour fast in which you eat normally on sunday and monday with your dinner at 8pm for example, then you eat nothing until 8pm dinner on tuesday (24 hours), followed by regular eating on wednesday, thursday, then maybe a fast on friday or saturday. however you want to do it.

          Another very popular way is the reduced eating window. For example giving yourself a 5 hour window to eat each day, say from noon to 5. Not an excuse to overeat, though even if you do, you’ll find you eat fewer calories. The truth is we all eat more calories than we really need, and if you have been eating primally you will learn to tell very quickly when you are over or under eating.

          Another less structured way is to occasionally just skip a meal or two. There is a benefit to this, but I prefer the 24 hour gap periodically (twice a week). You need that amount of time for the cleansing and such.

          Here is a free e-book it goes into explanations of IF and also some sample schedules you can try. It really has all the information that “Eat Stop Eat” has, but free. (Eat Stop Eat goes into more detail.)

    2. I haven’t been fortunate enough to see any study substantiating this. I would greatly be appreciative if you can share with me any study you might have seen to back up that Intermittent Fasting causes a decrease in testosterone and absorption.

      Thank you!

  15. Energetically I think many people have a tendency to over eat from time to time–the food just tastes good or you were really really hungry. Fasting for a meal or two or even a day helps move through the stagnant food sitting in your intestines and can make you feel better. My husband refuses to change his eating habits but he loved the alternate day “fasting”…

  16. Mark, I am still confused on the whole concept of IF. I mean, I get what it’s supposed to do and all, but where I have problems is skipping a meal puts me in a danger zone to pig out (literally) the next meal. For instance, on Saturdays I forget to eat a late morning snack and then lunch. I eat a nice big 4 egg and 2 slice of pasture raised bacon along side with a 1/2 grapefruit. This meal fills me up but then by 3pm I am starving. I’ve been doing this for years and I believe that is what got me in this mess. (weight gain). After reading your book in April, I started seeing results because I was eating more often and I ignored IF. I thought this was the reason for losing more weight and getting stronger. Saturdays became more difficult again so here I am once again skipping meals on weekends and pigging out for dinners. Result, I am slowly add more pounds as a result.

    One thing to note is that you spoke of discipline. Its so hard to have had issues with weight and using the discipline that got me in this mess. That part is really hard to overcome. Working out is the easy part…

    1. It’s good that you’re mindful of how IF affects you. I say that IF is a nice addition to the PB but not a mission critical component. If you’re finding that you hit your ideal body composition without IF and that IFing is difficult/torturous and means you put weight on then I’d simply skip it.

      With regards to pigging out, if you do a FitDay breakdown you may find that your regular meal plus your pig out meal may still not equate with a regular day of eating.

      On the issue of hunger and IF – many people note that they’ll feel hungry right around the time they usually eat but that it passes. Have you experienced this?

      1. Mark,

        I’ve read about the hormone grehlin and understand it has a lot to do with the transient feeling of hunger around the same time meals are typically eaten. This feeling, however, almost always passes within minutes.

        For those unfamiliar: Grehlin is a hormone released from the stomach wall during habitual meal times. This hormone appears to stimulate hunger, which makes sense from an evolutionary standpoint — it encourages continuous intake of nutrition for survival. Some people have said that regular meals (the standard 3 square meals, or worse, today’s mass recommendation of eating 4 to 6 smaller meals a day) makes it harder to control grehlin release, which leads to constant hunger and overeating.

        I think there might be something to this, as so many people are told by their trainers, nutritionists, and other so-called health experts to “graze.” The result is that most people lost the ability to differentiate between true biological hunger and just behavioral hunger. Also, what started out as 4 to 6 small meals a day often end up as overfeeding in a phenomenon sometimes called “calorie-creeping.” Put grehlin and calorie-creeping together and you have bad news.

        The 3 square meals is a modern tradition; the 6 small meals is simply a lie… or a band-aide for wildly fluctuating insulin levels from eating grain-based carbohydrates and processed foods.

        1. There is of course a reason I ended up grazing. It all has to do with pre and post workout meals.

          My current schedule is as follows:

          9AM: 2-3 eggs and Turkey, Spinach, Red peppers, coconut butter.

          12PM: Lunch (Always Primal)

          3:45PM: Pemmican Bar (Grass fed Beef tallow, dried berries, Jerky), half an apple.

          4:30 Crossfit WOD (Work out 1)

          5:15PM: Half of an apple, Whey protein, spinach.

          6:00PM Olympic Lifting Workout

          7:00PM: hard boiled egg, broccoli, almonds.

          7:20PM: Dinner (Always Primal)

          10:00 Whey protein, Almond butter (2 TBSP)

          So, as you can see I end up eating lots of little meals. Keep in mind this is 4-5 days a week and on off days I eat 3-4 meals, and eliminate the pre and post whey.

          What do others do? I notice a difference in my strength output when I’m not eating.

      2. Mark, I have noticed that the hunger pangs I experience are more physiological than mental. I have a pretty great grasp on my mental ability and am sometimes too aware of what is going on in my body. (I once actually felt slow digestion throughout my system during a long meditation session) I’d have to say that there are times on the weekends I get that “low blood sugar” experience. I sit with it for 5 minutes and it gets pretty rocky. But I can relax through it and it goes away. Saturdays and Sundays are so difficult to keep that 4 meal schedule that I enjoy during my work week. I find that by noon or so, I am hungry but only because my brain is working on memory to eat and not an actual physical experience.

        Regarding “ideal” body composition. Heh. Come on, ways to go bro. Ways to go! I’ll get there. 7lbs a month. That is all I expect. Still around 200 (from 250) It’ll happen, 2010 is going to be an amazing year. 1 full year of PB style! Thanks again Mark!

    2. I had this problem for a while.

      I would cook up a big meal and be full and satisfied. Although within an hour’s time, I would get hungry again. Then when I went to bed, I would get really thirsty.

      After some time I realized to drink a few cups of water with my meal. Turns out that since I was eating less frequently I was also drinking less water. I realized that the hunger that returned after the first meal was not hunger, it was thirst!

      I hope this can help you out Daniel. Good luck!

      1. I need to remind myself to drink more water. I do not hydrate enough. I never over do it, but I need to at least honor it more. Thanks!

  17. I have been experiencing steady weight loss due to eliminating dinner most of the time. I will eat a cup of soup for dinner or just skip it altogether and since I started doing that my weight has been dropping (albeit slowly) every week. On the weekends I only eat 2 meals per day and space them out at least 5-6 hours. I feel a lot better since doing that and have not had cravings or desire to nibble or graze.

  18. Has anyone heard about the risk of gallstones when fasting?
    I suppose the mechanism could be that the bile sits in the gallbladder for a long time as it doesn’t get emptied when fasting which can lead to development of gallstones.
    I think the gallstones would occur more if you constantly ate low fat.
    What are others thoughts on this.

    1. Sue, Interesting you mention this. One of my co-workers was also in on reducing weight and started a tough working out routine. He lost over 60 lbs in 8 months and looks great. Yesterday he told he that he was having his gall bladder taken out. He said “Be careful of losing so much weight. You’ll damage your gall bladder.” This is making sense. He went all “low-fat” packaged foods and I’ve been doing it with healthy natural foods with fats.


  19. I have always felt better IFing even before I knew that’s what it is called. Because I don’t get hungry until hours after I get up I would often skip meals and fast 15 hours or more. And when suffering from what was erroneously diagnosed as IBS and turned out to be gluten intolerance, fasting with warm water was the only thing to bring relief.

    When fasting for 24 hours or more I find the first day hard but I know it’s all in my head because it is triggered at “meal time” and it gets easier as time goes on.

  20. I’ve been doing the alternate day diet for a week, consuming three Atkins Advantage shakes on “down” days – about 20% of normal caloric intake. It’s been very easy so far. I’m not hungry on down days at all, and I eat normally on “up” days.

    Doing two weeks of alternate 20 percent down days is supposed to switch on the a gene called the “skinny gene” or “rescue gene,” according to Dr. James Johnson, who developed the “UpDayDownDay Diet.”

  21. For the last few weeks I’ve found myself eating just one meal, mostly out of convenience. Working 2 jobs makes time for cooking pretty scarce. So I’ll generally get up, run out the door to work, work all day, and eat when I get home. I can eat until I’m full and not really worry about the details.

    Since I haven’t really been exercising either at least my weight has stayed pretty much constant. Hopefully when I squeeze in some workouts my body composition will improve. For now though, the benefits of eating just a single late meal is that it saves both time and money.

    Since going Primal, I find skipping meals to be relatively easy.

  22. Great topic!

    I enjoy fasting for the self-discipline derived from this and, like it had been mentioned before, increased energy , etc.

    My weight is a little on the light side and I am trying to gain muscle mass. Should I continue IF where I skip one meal twice a week on different days? I am 56 yrs. old and gaining muscle is a challenge. Just trying to regain 10 lbs. of atrophied muscle but wondering if IF is the wise thing to do. I enjoy IF but will it impede muscle growth at my young age?

    1. More of the same
      I’ve been fasting weekly (36hrs) for 6 months, added PB the last 3 months, and dropping lbs is effortless. Now it’s time to add muscle. I’m hoping I can continue to lose fat thru the fast, while overeating for muscle growth the rest of the week. Any thoughts? (51yrs old, primal workouts)

  23. I think the key to avoiding a post-fast pig out session is maintaining a primal diet on days between fasts. Eating primal and reducing insulin sensitivity should preempt the ravenous feeling post-fast. I find that when am staying strict about avoiding non-primal foods, I feel well-conditioned to fast. If I’m craving anything post-fast, it’s more along the lines of strawberries and apples– not some food coma-inducing splurge. It is as if my body forgets about non-primal cheats or even primal treats.

    I’m a little surprised at how many commenters want to see a scientific study to support effects of IF. I guess it highlights the tension between the MDA mantras of questioning conventional wisdom and looking for convincing scientific underpinnings. Studies or not, I’m not bothered: if it works, it works. I see the results in my own body.

    I have been studying like crazy for law school exams over the last month or so, and eating quasi-Warrior diet. I’ve dropped about five pounds of body fat, continue to make strength gains, and look more cut. It’s improved my mental clarity and focus throughout the day, and my large meal at night effectively signals my body to start winding down for sleep. This morning I decided to “eat plenty” the day before my exam and I am markedly less energetic and focused; hence, the blog commenting. IF helps me meet my goals, and that is sufficient evidence for me.

    1. I wasn’t too surprised when commenters starting requesting scientific back-up for IF

      This happens all the time on all sorts of health/fitness blogs.

      often the debate devolves into a “my study is better than your study” kind of argument.

      I prefer to use research as a signpost directing me towards a potential solution to a problem.

      If the research is decent, I am willing to use myself (or clients) as a guinea pig to test out the research findings.

      If they work for me…great
      If they don’t, they don’t

      No need to get all caught up in the dogma between IF and Primal and High carb vs Low Carb or Endurance Training vs Interval Training

  24. Back in the ‘old days’ about 20 years ago I was studying off-campus and attending weekend schools once a month where the available food was really bad. I started to fast those weekend – evening meal on Friday and nothing but warm water until breakfast on Monday.

    18 years ago I remarried and. like all good things, the weekend fasts became a thing of the past and eating more became standard.

    I am now much heavier and would like to fast again but have been ‘warned off’ because of a near heart attack 9 years ago and a heart attack nearly 8 years ago. Apparently fasting is believed to not be a good idea for people with a history of heart attack but I suspect that my GP and cardiologist would never support fasting. I would be interested in hearing from readers who have information on fasting for people with a history of heart attack.

    I am also on rat-poison ( Warfarin)daily for the next 6 months and the recommendation then is to eat regular and similar meals to keep the blood clotting factors constant. I recently developed blood clots in my leg and lungs after lying in bed with a fracture; hence the Warfarin.

    However what I am trying to say in the middle of all this rambling is that the weekend fasts once a month; followed by light eating for 2 or 3 days, was a great way to fly, so to speak. I recommend it and when I get off the rat poison I would like to start it again.

    Then there is also the Every Second Day Diet; based around the concept that dieters should eat well one day and then fast the next.

    Oh, by the way, I have refused to take Lipitor and have been off it for nearly 2 years; threw out the margarine and canola oil; and started eating much more saturated fat since reading “Nourishing Traditions” by Sally Fallon. I was attracted to your book Mark because of your recommendations concerning meat and grains which basically parallel Sally’s ideas but was turned off somewhat because you sell and promote supplements.

    But, each to their own belief and I do take vitamin B6, B13 and Folic Acid daily as well as 20ml of Cod Liver Oil, yoghurt, garlic, ginger, chilli, raw honey and Turmeric with raw apple cider vinegar.

    I’m 68 and my cardiologist thought that I was 56 ( someone had entered my birth date incorrectly ) and I have 3 teenage children to age me… no I mean to keep me young.

    Anyway I support the occasional fast and when working physically I don’t see the need to stop and stuff oneself with lunch when water will do. Of yes when fasting I always drank a cup of water on the hour every waking hour – I carried a thermos of hot water with me. Don’t drink tea or coffee as they will stimulate appetite. I have fasted for a month drinking only warm water. I believe that one can go without air for 3 minutes, without water for 3 days and without food for 3 months drinking water every hour.

    This short comment has developed into a massive missive so it’s time to away.

    To your successful intermittent fasting.

  25. I have been doing a ~32hr, water-only fast 3 days a week (M,W,F) for the last 5 months. Basically, I stop eating in the evening before going to bed and then skip eating the entire next day. I find it extremely difficult to stop eating during the day once I get started, hence I stop when I go to bed as usual.

    Initially, my fasting required some mental energy to get over the psychological hurdle/habit of eating every few waking hours. I would liken it to conscientiously holding one’s breath when swimming under water. After a week or so, the effort required to fast pretty much disappeared. I also stopped noticing much in the way of physical differences/sensations between eating days and fasting days. Although I now have a preference for performing physically or mentally challenging activities on fasting days if I have the option.

    If you want to try IF’ing, you might want to try different approaches because there are obviously personal preferences involved based on the preceding comments.

  26. Don’t you ever get headaches when you don’t eat regularly? If I skip lunch I’m sure to have a pounding headache by 3 p.m.

    1. No, I don’t. Are you going cold turkey on caffeinated drinks, maybe?

      1. No, I don’t. I drink one coffee per day, if at all. It seems to have something to do with my bloodsugar level. At least I can’t think of any other explanation.

        1. Sometimes I get a headache around 36 hours without food which caffeine will not cure, but I am not experienced with fasting. I suspect it will go away as the body becomes more used to fasting.

  27. I am very interested in these topics. When I was in college I lost a lot of weight without really trying. I basically like most college students slept a lot during the day which meant I didnt eat until late and when I did eat again like a college student it was whatever I felt like. Late night trip to Denny’s or pizza def not the healthiest. I found it very strange that I was able to lose 30 lbs this way. As an adult I have put on a lot of weight. Im about 50lbs overweight and have tried calorie restrictions, low fat diets and have had no luck. I have done a few fasting periods of about 3days and lost 6lbs each time felt great which has me searching online for my next plan of action. Im thinking by going back to my college eating habits while changing the junk food to primal will be what works best for me. It makes sense when you sit and do that math that you are still eating less over time. Who would have thought… Thanks for the info!

  28. I have fasted for many years, usually 3-5 days, also every other day for a few weeks (the hardest for me), and twice for 30 days. And I mean fasting as in only water; juice is high carb food and not really fasting.  Usually the pattern is 2-4 days of using up the body’s stored sugar; it’s during this time that most people will get headaches, especially if you do lots of carbs and caffeine Once the body kicks in to using fat for fuel, and making ketones, then hunger disappears and energy goes through the roof.  One effect is that you need a lot less sleep, which I used to worry about since I have had problems getting enough sleep. But this is the Paleo-evolutionary response to heighten alertness, and is normal.  
    Fasting has been shown to clean the body of all kinds of junk, as it were, that leads to the so-named diseases of civilization/modernity. 
    The hard part for me is not the fast, but coming off the fast, for the biological programming triggers big cravings if I start eating any carbs besides the green veg. So I’ve learned to stay very low carb for at least as long as the fast.  This is also why fasting to lose weight is a usually a disappointment, but the many health benefits are more important. BTW, I’m often told that I surely can’t be in my sixties; I’m very healthy and my skin is quite good which I attribute to fasting (& moisturizer).  (I know that sounds boastful, but I’m just stating my experience.)

  29. About 20 year ago I fasted one weekend a month – nothing except water on Saturday and Sunday. (Water every waking hour)

    In 1992 at the age of 51 I remarried and started a family (3 kids) and my dietry habits changed over time. 25 kg and a heart attack later I feel the need to reclaim my smaller healthier body.

    I found that if I had even a cup of tea then it was difficult to not eat – as long as I stuck to water only then not eating was not a problem.

    I have been reluctant to fast since my heart attack (2002) but I gather that it is probably OK. Any comments on that welcome.

    I will be 70 years of age in 18 days and still working – I have to with 3 kids in High School.

    I went 30 days fasting in nce and only started eating because of pressure from ‘concerned others’. No hunger at all. I then eased back into eating over the next month. (Apparently the rule of thumb is to eat carefully for at least the saame time as the fats)

    It seems that we can go without air for 3 minutes, without water for 3 days and without food for 3 months. When fasting one should drink water – I found warm water every hour best for me. During my weekend fasts I was attending weekend classes at University as part of my off-campus study for my Diploma of Education and carried a large pump-top thermos full of warm water. I started the fast because the available food was not worth eating.

    I was on Lipitor for many years after my heart attack but disposed of them about 3 years ago. I have also reduced my blood pressure medication to half of the smallest dose tablet.(My caardiologists states that the dose is too small to work – my GP insists that I take something. This is the same GP that wants me to take Vitamin B6 and B12 with Folis Acid so he is open to alternative answers.

    I eat: Garlic, Ginger, Chilli, tumeric, honey, apple cider vinegar, LSA mix, cod-liver oil, yoghurt and 2 raw eggs for breakfast every day along with some vitamins and most days I only eat lunch out of habit or because someone puts it in front of me. I am part owner of a Chinese restaurant on the ground floor of my office building and am ‘expected’ to eat there sometimes.

    I have rambled on but does anyone care to comment of fasting after a heart attack?

  30. I do a version of this – I eat very low carb, and then ‘bust out’ on the occasional day or two with ramen or Tteokbokki, dumplings or bread, potatoes, sometimes chocolate ,(not all on the same day!). Then go back to the low carb.
    So usually about a fortnight on low carb, give or take… I listen to my body, and have a carb day when I crave carbs. I find this can vary with hormonal fluctuations – THANKS Menopause you a-hole.
    I’ve lost about 30kilos in 4 months, and I do not eat low calories on the low carb days, lots of protein, lots of fibrous veg, and lots of fats in cheeses and whatnot. No deprivation at all.
    When I eat carbs, I no longer find that I put on weight for just a day or two of eating those things, though I did at the beginning.
    Works for me.