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

Fasting Makes You Active

It’s a familiar image we might attribute to stereotype: a sluggish, maybe portly individual lying prostrate on the couch, his/her front littered with Dorito crumbs. Could there, however, be truth behind the picture? Is there indeed a connection between incessant snacking and chronic slothdom? Or considered another way, is there a connection between fasting and being active? As a long-time fan of intermittent fasting (and a believer in the research behind it), I’m convinced. A study out this month sheds even more light on the relationship between lethargy and continuous eating.

For decades now, conventional wisdom has told us that we should eat regularly throughout the day to keep our blood sugar steady. With three regular meals and at least two snacks, we’re counseled to keep our bodies in a perpetual postprandial state. However, newer research, including this month’s study from ETH Zurich, questions this assumption. Scientists focused on the opposing relationship between a transcription factor, Foxa2, and insulin. Foxa2 is found in both the liver and the hypothalamus, the central command for hunger regulation. It has a hand in the expression of two eating and physical activity related neuropeptides, melanin-concentrating hormone (MCH) and orexin. When insulin is present, as it is during and after eating, Foxa2 and the related MCH and orexin are reduced. However, fasting mice showed consistently high levels of Foxa2, MCH and orexin. The researchers then found that “hyperinsulinemic, obese” mice showed reduced Foxa2, MCH, and orexin, regardless of whether they had eaten or not. When the scientists bred mice with continually active Foxa2 (immune to the counter effect of insulin), these mice showed high levels of MCH and orexin – and a correspondingly high level of physical activity whether they had eaten or not. The specially bred mice had low body fat as well as higher muscle mass.

Consider this study another nail in the coffin of conventional wisdom. (It also goes a long way in explaining the snacking couch potato association.) Fasting, even short, between-meal breaks, promotes the activation of Foxa2 and the resulting formation of MCH and orexin – as well as their activity-inducing effects. A simple survival principle explains this: a hungry animal needs to get up and move to find food. On the other hand, if we are constantly swimming in the insulin of eating and post-eating states, we’re undermining our own motivation (and biochemical stimulus) to get up and burn off what we just ate.

CW encourages us to never skip breakfast, bring along a mid-morning snack, make time for a good lunch, grab a mid-afternoon nibble and then have a good dinner. Oh, and if you can’t sleep, you’re supposed to have warm milk and a banana before bed. Our bodies are either eating or processing what we ate. There’s never a recovery period. Nary a resetting opportunity. We’re so focused on the hobby horse of “stable” blood sugar that we’ve forgotten that there’s more to the biochemical story of balanced energy. We make ourselves feel perpetually full to the exclusion of feeling anything else. (How about light, energized?) We continually raise our blood sugar and insulin levels and, in doing so, turn off the body’s chance to activate or upregulate other key substances that promote energy balance – and as this study shows, the physiological motivation to be active. Simple advice: skip the snack. (Besides, dinner never tasted so good as it does on a healthily empty stomach.)

Let me know your thoughts. IFers – have you found this principle to be apparent in your own experiments? Thanks for reading.

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 find that when I fast I am more likely to curl into a ball and do nothing – no energy to do stuff.

    AlyieCat wrote on December 30th, 2009
    • probably because you are not yet adjusted to the process. I’m a regular now and I can last quite a while (up to 3 days) without serious hunger pangs or drops in blood glucose. you could just be… weak.

      wd wrote on December 30th, 2009
      • IT fasting is a great time for the body to rest the digestive system … if you are new to fasting of any kind, I have found that eating my last Primal Meal of the day by 5pm and going to bed feeling a bit hungry helps me sleep better and feel alive and energized in the morning…. practising this as consistently as possible you might find fasting a joyful pleasure rather than an unpleasant experience…

        Sygun wrote on December 31st, 2009
    • I was the same before switching to a [more] primal eating style. I haven’t tried a full day IF or longer yet, but the single skipped meal IF brings zero loss of energy, zero mood swing (from decreased blood sugar) and a feeling of intensified alertness/awareness. My brain (not my body!) keeps trying to tell me it’s “meal time” and therefore I should eat something – despite the fact that I’m NOT hungry – so I sometimes walk or cycle just to distract my brain :)

      Ben wrote on December 30th, 2009
      • this subject intrigues me. for several years now, i’ve noticed my body go through cycles of hunger and not-hunger. i’ll be eating normally and then randomly (at least, to me) for a week or so i won’t actually feel hunger and have a hard time reminding myself to eat. then after several days of this, i’ll swing to the opposite end where i’m hungry all the time. i’ve never noticed energy changes with the swings. only when i try to mess with it, like, make myself eat regular amounts when in the non-hungry phase or not eat when in the hungry phase. and it seems to work to go w the flow – ‘binging’ when in the hungry cycle seems to trim me up, counterintuitively.

        Amy wrote on January 20th, 2011
  2. Great post! I used to be one of those who was under the influence of CW. I thought I had to eat every 2 hours. It was a struggle because I was hungry all the time and I never could get my body fat % down. Now that I follow a PB I never worry about the next meal and I’m happy with both weight and Body%. Thanks Mark

    Bryan Cash wrote on December 30th, 2009
    • I also used to eat every two hours (prior primal) and NEVER loss weight lol, or body fat. Ever since the primal diet I noticed my calorie intake is fine, and I don’t get so hungry and so I got curious about fasting and came accross Marks wonderful posts, and will start my first fast tomorrow :) I am actually excited. BTW since primal I have lost 17lbs and dropped 7% bf to a wonderful point of 125lbs and 20.6% woo hoo. I find this so amazing.. I too never stress about my next meal and don’t binge crave… I love the experimenting of awesome refined carb free recipes… very fun. LOVE IT. Can you tell I have mega energy, and at the end of the day AND caffeine free!!

      Desiree wrote on June 7th, 2011
  3. I really want to believe that when I skip the between meal handful of dried figs, coconut and or handful of almonds that I am helping my body regulate insulin properly. However I struggle with fasting even between breakfast and lunch (about 4-5 hours). This morning I did eat 1/8c steel cut oats with flax, 1 pear, and 2 eggs cooked in bacon fat at 7am. Its 11:30am now and I am so hungry that I am afraid that lunch is going to be a gorge-fest on more grains (pregnant wife loves 1 slice of Roggenbrot per day). As a matter of fact, yesterday I had to perform magic on myself to give an illusion that I was not hungry by drinking so much water because I decided that after dinner [7pm] until 7am I was not going to consume anything. I did, but I was awake all evening, I had trouble sleeping and my dreaming was so lucid I thought I was reincarnated as bear and ate my dog.

    Mark, I really want to subscribe to IF, really, but I note that my sprinting, strength training or any real deep interval training suffers.

    Could I not be eating enough at my normal B, L, D meals? Should I step up more fat?

    Daniel Merk wrote on December 30th, 2009
    • Daniel,

      Could be that the 35 +/- grams of carbs in your breakfast are causing the problem. If you had had 4 eggs and no oats and/or pear, you might reduce insulin and, hence, the hunger that accompanies. As I say here, it takes about three weeks of steady low carb eating to “reprogram” the genes to preferentially burn body fat. When that happens, hunger subsides and energy stays even and balanced.

      Mark Sisson wrote on December 30th, 2009
      • Weird, 2 days of oats (we’re talking 1/8c dry) and I am beginning to notice a scratchy throat and a bit of the sniffles. So crazy because I don’t feel like a cold or anything. I have been really off the grains for a long time now, but thought I’d change things up as long as I keep the carbs under 150ish. Time to re evaluate. Thanks!

        Daniel Merk wrote on December 30th, 2009
        • Daniel, I would definitely say increase the protein and fat, with or without the carbs. In fact, with the carbs the protein and fat will slow down digestion and prevent blood sugar swings, so you may be able to go longer without eating. But if that still doesn’t work you might want to cut out some carbs as Mark suggested.

          It does take time to get used to, though. I was a chronic eat-eight-small-meals-a-day person about a year ago. I’ve finally got myself down to 2-3 meals a day, and in the past couple weeks I’ve been dabbling in IF as well.

          It takes some adjustment to consume the right amount of food in fewer meals. I like the idea of an “eating window” of a couple hours or so. It makes it less of a strain to consume enough food to keep hunger at bay for a longer period.

          Elizabeth @ The Nourished Life wrote on December 30th, 2009
        • Daniel, I concur with what Elizabeth and Mark both said. I’d only add that you really should try increasing your consumption of saturated fat. Many, including myself, have found a hperlipid diet to be incredibly satiating. I usually go about 15-17 hours between dinner and lunch with nothing in between each day. I eat a lot of FAGE Total yogurt, eggs, bacon, full-fat meat, cheese, etc., and this satiates me for a LONG time. Before starting lacto-paleo, my breakfast was whole grain cereal. I was ravenous by 11am and remained irritable and cranky until my lunch fix. And so on throughout the day. The idea of fasting was a complete turn off. After going lacto-paleo, and now that my body is in ketosis, I find fasting is a breeze. A few times a month I’ll go 24 hours like it’s no big deal. I did so on ThanksGiving day this year. I drove down to San Diego to visit my cousins, and hadn’t eaten since the night before. TG dinner was at 4pm. When I arrived at 1pm my aunt asked if I wanted anything to eat and I said that no, I hadn’t eaten since the night before but wasn’t very hungry so I’d wait for TG dinner. She was shocked and thought I must be ravenous, but to her disbelief I repelled the snack foods she waived in front of my face.

          I wouldn’t have believed this about myself just a year ago. Now it’s second nature. Go true primal (lacto is okay if you tolerate it, and fermented full-fat lacto is great!). You’ll probably find your energy levels increase dramatically, especially when well fasted.

          Aaron Blaisdell wrote on December 30th, 2009
      • I so agree!! Fruit especially seems to be a trigger for me. Berries I can handle, but even those have to be kept to a small portion. Oatmeal and a pear for breakfast and I’d be starving within an hour….adding the eggs might allow me to last 2 hours. But give me a couple of eggs and a few strips of bacon and I’m good for at least 4-5 hours!

        Alcinda Moore wrote on December 30th, 2009
    • Daniel,

      I don’t know how long you’ve been going Paleo, but I’d recommend not forcing the fasting issue until it becomes easy for you.

      My wife, for example, took about 6-8 months of Paleo eating before missing breakfast was realistic for her. It just takes some of us a long time to restore our bodies ability to mobilize fat and regulate blood sugar.

      Eat lots and lots of fat, avoid crap, and only eat when you’re hungry. After a while, months to years maybe, fasting will happen naturally.

      Don’t force it or you’ll turn yourself off to IF forever and miss out on the great benefits!

      In answer to MDA – I find I’m jumping out of my chair all day when I fast, I’m doing one right now!


      Bryce Lee wrote on December 30th, 2009
      • I absolutely agree with this, Bryce. It took me nearly 5 months on the PB (at near 100% compliance) before I was ready to IF. When I was ready, it happened almost by itself, without effort.

        For me, it was a combination of learning to trust my body not to go into chew-my-arm-off-hunger mode if I skipped a meal, plus learning to identify (and wait for) genuine hunger rather than eating “because it’s mealtime,” plus understanding the science behind IF.

        I started by stretching out the time between dinner and breakfast to 12-15 hours most days. Then, the day before Christmas Eve, it happened…I had a late lunch at 3:00. Worked out in the evening. Wasn’t hungry, so didn’t eat dinner. Slept well and woke up early, worked out again, and didn’t eat until company arrived for brunch at 10:00. Totally easy.

        Give it time. Let it happen. :)

        BarbeyGirl wrote on December 30th, 2009
        • Another thing — learn to accept hunger. It’s okay. All the world’s food will not evaporate if you wait half an hour to eat…but likely as not, your hunger WILL evaporate.

          This only works for me when carbs are low and grains non-existant, but it’s wonderful! I just now went through an “I want dinner” phase that lasted about 20 minutes. I’m hungry, but not starving. I’d rather wake up tomorrow with that wonderful, light, fasted feeling than indulge in a snack tonight. So, I didn’t eat…and now the hungery feeling in my stomach is settling down.

          This is very cool, Mark. Thanks so much for helping me get off the carb carousel!!

          BarbeyGirl wrote on December 30th, 2009
    • My own experience is that it’s all about adaptation. I don’t follow PB explicitly (although now reading about it with interest) but I’ve been practising daily IF (anywhere from 19/5 to 23/1 schedule, usually after 6pm) daily for most of the last decade. I’m also a regular exerciser (mainly Heavyhands and bodyweight) and hill-walk, bike and ski, mostly without the need or desire to change my usual feeding schedule.

      Nowadays I associate fasting with energy and clarity, for work, play, or exercise of whatever level of intensity is needed. Eating, by contrast, is followed by a noticeable (though not necessarily unpleasant!) post-prandial period of relative sluggishness, and poorer performance should significant exercise demands occur at these times.

      I assume that numerous changes have occurred in my physiology over time that account for these effects – not being expert in these matters, I can’t claim to know exactly what they are. But I suspect that we can’t know what our bodies (or psyches) are capable of under any particular circumstances until we have had time to adapt to them, and this makes such matters impossible to assess over the short term.

      David wrote on December 30th, 2009
  4. Great post Mark. It certainly makes sense and I am sure everyone here can attest to having more energy when in a fasted state. People who eat all the time, or as many call them, grazers, don’t stimulate those processes that tell them to get up and move to food. Their bodies think food is and will always be around.

    I am currently bulking and trying to get all my calories in a 4-6 hour window. It’s nice being able to feel hungry, prepare and gorge. I’m also not convinced about pre and post workout nutrition leading to higher gains.

    BlazeKING wrote on December 30th, 2009
    • Has anybody heard of the warrior diet? seems to comply with fasting all day and having one meal at night time.

      Diego Paparella wrote on January 1st, 2010
  5. I have been experimenting with fasting and I find if I eat breakfast and lunch I can skip dinner. I usually try to eat between 9 am to 2 pm and not eat the rest of the day during my work week and 11am to 4pm on the weekends. I feel great. I have found that dinner seems to be superfluous and I eat it out of habit or boredom. Most intermittent fasters seem to skip breakfast but I get up a 530am and there is no way I could work all day and last until dinner.

    thecarla wrote on December 30th, 2009
    • as far as I understood it you’re not really reaping benefits in full from the fast unless it’s around 24hours w/o caloric intake. someone strike me down if this assumption is incorrect.

      wd wrote on December 30th, 2009
      • [quote]Fasting, even short, between-meal breaks, promotes the activation of Foxa2 and the resulting formation of MCH and orexin – as well as their activity-inducing effects.[/quote]

        From above. I’ll trust that Mark did his research 😉

        hannahc wrote on December 30th, 2009
        • I find it hard to believe that you quoted the article above… actually I’m flabbergasted.
          Perhaps it wasn’t in the article? {Wink}

          wd wrote on December 30th, 2009
      • The 24 hour fast is the least prevalent form of fast. The most common is the eating window fast (fast 19 hours, eat in a 5 hour period), or the one meal a day (23 hour fast, eat in a 1 hour window). You reap the full benefit by just giving your body enough hours to process and reset. 36 hours is also great, beyond that and while there is still some benefit, the law of diminishing returns sets in. I believe 72 hours is where metabolism really slows down and your body starts preparing for famine mode.

        The point is any break you give your system is beneficial, and you will notice that you don’t need as many calories as you thought you did. You sh*t most of the overage out anyway. You’ll notice less frequent bowel movement when IFing, as your body extracts more of what’s needed without rushing to evacuate.

        Big IF fan here.

        void_provocateur wrote on December 30th, 2009
      • As a diabetic who test blood sugar hourly when making dietary changes, I can confirm that a 12-hour fast makes a difference in my blood sugar levels. I’ve been eating breakfast and dinner with no lunch for only about a week and there is a noticeable difference in my response.

        David wrote on December 30th, 2009
  6. I have stated this prior to finding your website as well as the benefits of IF. There would be days I would be laying tile, building cabinets or some other type of work only to find it becoming dark outside and realizing I had skipped all meals that day. At the time, I attributed it to a micro-calorie diet, and rather then eating well and properly, I simply ate less. It gave me loads of energy, but was probably not that healthy.

    Michael wrote on December 30th, 2009
  7. Hm…I do IF, but I find that the only reason I move around more during fasts is to keep warm.

    Meeses wrote on December 30th, 2009
  8. I think you’re right on… although I don’t have enough IF experience to say definitively.

    I felt better and was more energized when I was IF’ing, but then I got the flu… so I don’t know if my loss of muscle was due to IF or being out of the gym – or both.

    I’ve always liked the higher activity level I have when I’m fasting, and as long as I’m eating clean, I don’t have any energy swings or cravings… and that’s with an 18-19 hour fast, on average.

    Adam Kayce wrote on December 30th, 2009
  9. Great post and it totally reinforces my experience. I eat twice a day, once around 10am then dinner 6-9 ish depending on the convenience of it. Also do 2 24+ hour fasts per week. I’m quite active and feel fine energy wise. I do occasionally succumb to the hunger and snack on some nuts and cheese, but not too often. I am still carrying 15# of spare tire fat and wonder if by my body having a ready energy source to tap into that keeps me going and all the sluggish folks are skinny little punks?
    Thanks for all the effort.

    Ken wrote on December 30th, 2009
  10. I’m replying to Daniel Merk’s post — Daniel, maybe you’re very carb-sensitive. I am too and I would find that quite a carby breakfast, with the oats and the pear (tried to eat a pear last month and found it too sweet). Dried figs are also very sweet. Maybe eating just protein and fat for breakfast…?

    Anne Scott wrote on December 30th, 2009
    • Interesting. For 4 months now I had been eating uncured bacon, and 4 eggs for breakfast. By noon I was not hungry and noticed I would not eat again until dinner. I thought that if I went back to doing “some” oatmeal I would change things up a bit but I think you are pretty much spot on– I am carb sensitive.

      Daniel Merk wrote on December 30th, 2009
      • I think 150 g. of carbs a day is a lot for anyone. If you do have insulin sensitivity issues then its way too much.

        David wrote on December 30th, 2009
      • Carbs at evening, or every few evenings. By morning, you’ll be in ketosis again.

        Protein, fat, and low-starch vegetables in the morning.

        Christoph Dollis wrote on September 2nd, 2013
    • I responded directly to Daniel, but I would definitely agree with Anne. Unless you have restored your insulin/carb sensitivity, I’d avoid oats and starches for a while. If you are hungry three hours after eating starches, then you are not adapted to them, and should give yourself a break for a while.

      An occasional piece of fruit, or weekly sweet potato, won’t derail your efforts to restore carb sensitivity, but dried fruit and oats in the morning will.

      Good call Anne.


      Bryce Lee wrote on December 30th, 2009
  11. When I’m active (which is pretty much all the time) I’m ravenous. Three meals a day don’t cut it for me; I’ve gotta have snacks.

    I gave IF a try once, and all I wanted to do was sleep.

    dragonmamma wrote on December 30th, 2009
  12. I work out fasted, I’ve played a day long tennis tournament in a fasted state with no drop in energy….only enhanced “senses” if you will.

    IF is much less scheduled for me know. Most days I eat only 2 meals a day. First one around noon or 1. Second anywhere between 6 and 8.

    As anything new….. START SLOW.
    Happy new year everyone

    Marc Feel Good Eating wrote on December 30th, 2009
  13. When I eat consistently throughout the day, I get really panicky. Maybe I’m crazy (ok I’m definitely crazy) but my anxiety is non-existent when I fast. For the last few months I’ve been thinking that “snacking” is sort of like an assault on the body. It’s helping me think twice before eating between meals.

    Shauna wrote on December 30th, 2009
    • I had incredibly bad mood swings when I was eating higher carb, so it definitely makes sense.

      Susan wrote on December 30th, 2009
      • I had major anxiety and panic attacks for years, on drugs and everything. They all vanished with low carb. It was amazing. We’re not alone.

        Louise D. wrote on December 30th, 2009
  14. I find this to be absolutely true. I typically eat only breakfast and dinner, sometimes just dinner. I find I have more energy than when I have 3 squares. Not to mention when I fast for any duration I’m more apt to break into a run rather than walk. Even if it’s from my car to the front door.

    Diana Renata wrote on December 30th, 2009
  15. IF makes everything easier throughout the day. I always take my midterms and finals fasted because I feel much more awake and alert and I always try and go to Crossfit fasted between 12-16 hours. Granted, eating primally I never really feel sluggish. Even when I overeat I still feel like I could go sprint if I needed to.

    Accipiter Circus wrote on December 30th, 2009
  16. Today I did 5 x5 sets of military presses followed by 10 rounds of deadlifts (about 50% of my max) followed by 10 burpees at 6 am. It’s now 9:30 am and doing an IF til noon. Will this have a negative effect on muscle gain? I am trying not to lose weight but am trying to gain muscle mass (I’m 56 years old-have lost some muscle mass)and lose BF “love handles”.
    Will IF or longer fast after a workout help me reach my goals (gain muscle and lose BF?

    David wrote on December 30th, 2009
    • I wouldn’t worry about losing muscle while IFing. You would need to fast for up to 72 hours for that to happen. Make sure you are eating a lot of fat and a lot of protein when you do eat. Going IF and Primal is like going on a ketogenic diet. hell yes you’ll lose body fat! Just maintain your training and you will maintain and even grow your muscle.

      If you can, I would recommmend the book eat stop eat and it will explain how the idea of negative effects on muscle growth is falls. Body builders routinely IF for weeks before competitions (the bad ones starve which is stupid, but whatever).

      As always though, listen to your body, give it a chance to adapt. Once it frees itself of decades of bad programming you will see the difference. The only thing you’ll notice is, like everyone else, you get colder, but heat up fast when you get moving.

      void_provocateur wrote on December 30th, 2009
      • Thanks for the reply. I am in my mid – fifties and have worked on gaining muscle the past 2 years. But, no muscle gain. So, following PB religiously has been very productive with muscle gain. Been told to eat more protein but feel too stuffed and lethargic. So, maybe fasting can help me gain the HGH needed for muscle growth??

        David wrote on December 31st, 2009
        • Ooops. Following PB outline for gaining muscle has not worked for me, waaaah!

          David wrote on December 31st, 2009
      • About the getting colder thing. I am low in carbs (<100), but high in calories. What does it mean to be cold?

        Daniël wrote on August 10th, 2011
    • According to Art Devany, you will be better off not eating until noon — his theory is that eating after a workout will reduce the growth hormone response. On the other hand, many studies indicate that eating some protein and carbs (some say before, some say after, some say both) enhances muscular development. Supposedly, thirty grams of protein is the maximum needed, more than that provides no benefit, for a lighter workout, 20 gms would likely suffice. Myself, I prefer some protein/light carbs before a good workout and my body tells me whether it wants a booster afterwards.

      discgolfgeek wrote on December 30th, 2009
  17. I agree with Meeses. I don’t really notice much difference in energy level (usually not a problem). However, I definitely feel colder – esp. in the a.m. Perhaps “enhanced senses” as Marc puts it?

    Ryan wrote on December 30th, 2009
  18. I am new to PB. I have been doing well but wonder if I am esting too much fruit. I do berries once or twice a day, a grapfruit and then an apple or banana? Any help would be appreciated. Thanks!

    Jamie wrote on December 30th, 2009
    • That’s a hard question to answer because everyone is different, but what you mention doesn’t sound like too much, as long as you’re not loading down your diet with any other carbs, and as long as you’re eating plenty of fats and proteins. It’s important to listen to your body and see if you can tell how it’s reacting to what you’re eating.

      Elizabeth @ The Nourished Life wrote on December 30th, 2009
  19. So hunger pangs are good? I want to try IF, but I’m nervous. In the past whenever I go too long without eating, my stomach gets bloated and hurts like crazy. Can that really be good for you?

    Dee wrote on December 30th, 2009
    • Hahaha, I had those problems at the beginning too. But you have to realize there in lies your answer. Hunger pangs are not real hunger. Hunger pangs are muscle contractions. It is muscle memory. You have been eating a certain way for years, decades even. If you pay attention, the worst hunger pangs always hit at the time you were statistically most likely to be eating a meal. Your whol system starts working, stomach acids churning, before it realizes there is nothing coming.

      If you drink a cup of tea and then find something to do to keep you busy, you will quickly realize that the pangs do not last long. The bloating happens because your system is used to being stressed and it has mobilized all your internal chemicals out of habit. Think of that as withdrawal. When you see someone in drug withdrawal, how bad it is, is a good measure of how bad the drug itself is.

      Have you ever been so busy with work or having fun that you missed a meal? Congratulations, you have IFed. Where were you hunger pangs then? The pangs have nothing to do with hunger, they are just a ghost of your body trying to conserve energy by setting a schedule based on an inflated schedule you gave it.

      Give it a try, feel miserable, feel a headache, feel cold. I assure you after you feel the triumph that first time, the hunger pangs won’t feel that bad again, and after a few weeks, you won’t even remember what hunger pangs feel like. I haven’t felt a hunger pang in almost a year. And I do the most extreme form of IF. I eat 3500 calories each day, and then eat nothing the following day. One day on, one day off. According to conventional wisdom, I should be starving, lazy, racked with migraines, losing too much weight (I’m maintaining a steady 2 pound down a week), and losing muscle (I am actually gaining muscle size and definition).

      void_provocateur wrote on December 30th, 2009
    • I actually used to be the same way. I was severely carb addicted and if I did not eat breakfast, I would get incredibly nauseous and nearly throw up. I’m not kidding!

      All of that went away when I found my appropriate carb level (which is very low) and “real” hunger took over. I think all those horrible drops in blood sugar were to blame for the nausea. When I am going to IF I usually eat a very low carb meal before I do it, so I don’t set myself up for failure.

      Susan wrote on December 30th, 2009
  20. Im not sure if your familiar with the book “lights Out” Sleep, Sugar and Survival. I recommend it to anyone who wants to start “IF”. Make sure you have your diet down and get plenty of sleep (9 hours) and then through in a “IF” period. I try to run with a 15 hour fast before i start eating.
    Great as always Mark! Look forward to 2010.

    Charles Olson wrote on December 30th, 2009
  21. I try and do a 3 day fast every quarter, and through lent still fast on Fridays.

    Steven R. McEvoy wrote on December 30th, 2009
  22. Jamie, that does seem like too much fruit, at leat it is for me. I keep my fruit intake to a minimum, maybe every other day or less, and I restrict it to berries only, and just a half a cup at that. Treat fruit like a dessert that you imbibe in on an infrequent basis.
    Apples and bananas are very high in sugar…

    DB wrote on December 30th, 2009
  23. James-Try to limit your fruit intake, its like “candy” if your down with a low carb paleo diet, Try to stick with veggies, i run on about 50 to 70 grams of CHO a day since i switch to a low carb deal and cut of the fruit. Fruit also tends to give me GI problems so i treat it like a “cheat” and limit my intake to post work out meals.

    Charles Olson wrote on December 30th, 2009
  24. Hi Mark,

    I’ve been IF-ing for about a month now after reading about it on your site and doing some research on the benefits of IF and calorie restriction. I essentially skip breakfast, eat lunch at noon and dinner at 5 or 6pm and then don’t eat until lunch the next day except for some green tea in the morning. I am much more energized and am not constantly thinking about my next meal or snack- my appetite has decreased tremendously. I didn’t think I would be able to feel greater than when I started eating low-carb about 6 months ago, but IF is even better!

    This is a timely post for me, considering I was just home for the holidays and was unable to resist all of the delicious temptations- while I tried to stay relatively low-carb, I got completely off of my IF schedule. Since then I’ve noticed a remarkable drop in energy. I feel like I have some sort of food hangover. I couldn’t bring myself to go to the gym last night and could barely wake up for work this morning.

    So, after dropping IF for a week and experiencing such incredible difference in energy level and overall well-being, I think I am living proof of the theories presented in this article. Thanks for the post- it’s always interesting to learn about these biological mechanisms.

    Catie wrote on December 30th, 2009
  25. I have found a significant decrease in musculoskeletal aches and pains with IF.Granted it’s a n=1 but I am pretty observant and smart(also cute for an old guy.Even if you are sketchy on the scientific merits, IF is worth doing just to observe your relationships to food,desires,rituals etc.Brad Pilon’s ebook Eat Stop Eat is worth reading.

    OLDDUDE wrote on December 30th, 2009
    • I’ve tried to locate Brad Pilon’s book, but it seems to only be an e-book, correct? Can you get a print copy anywhere?

      Nancy wrote on December 30th, 2009
      • No, it is e-book only.

        void_provocateur wrote on December 30th, 2009
    • someone explain me this whole n=1 thing

      C2H5OH wrote on December 30th, 2009
      • n=1 is just a scientific way of saying that the statement is just based on personal experience. N is the number of whatever is being studied, such as 6,543 men and women in a study is written as n=6,543. In other words the commenter is saying the comment isn’t based on any large scientific study, just their own personal experience.

        Rodney wrote on December 30th, 2009
      • “n” is the unknown cause that equals the known result of “1.” So, OldDude is saying that he aches less (the known result, or “a”) and, due to correlation, he suspects that IF (a possible solution to “n”) is the cause. :)

        BarbeyGirl wrote on December 31st, 2009
        • LOL Oops, I meant “1” where I typed “a.” Just trying to confuse you!

          BarbeyGirl wrote on December 31st, 2009
        • Oh, good gravy. Laughing again…at myself. Listen to Rodney — he’s right.

          BarbeyGirl wrote on December 31st, 2009
        • NO. In statistics, “n” denotes the sample size and there was 1 person in his sample. He is just speaking of personal experience.

          Brian wrote on May 26th, 2010
  26. Thanks for the input. I have been very strict. Coffee,eggs with bacon for breakfast then eat thefruit while at work. Dinner has been a large salad w/almonds,cheese and chicken or steak and green vegatables. I also snack if I get hungry on almonds. I found fitday yesterday and I was in the 50-100 range ofr carbs. What are other snacks I could go toduring the day of I cut fruit down. Carrots and celery get old pretty quick. Any ideas would be appreciated. By the way, I am really enjoying this site. I feel so much better since going primal.

    Jamie wrote on December 30th, 2009
    • As far as the celery goes, It can get old, but I try to make it a bit more appetizing with Almond butter. Take some raw almonds and put ’em in the food processor until they turn to butter. It can take 5-10 minutes for a cup. I add one teaspoon of extra virgin olive oil. for more creaminess. Then I add one tablespoon of 100% cacao powder, and a few drops of Stevia. Spread in your celery stick. Tasty and good for you.

      DB wrote on December 30th, 2009
      • Boiled eggs, cold roast beef, cold chicken, all lovely snacks at work. I make mayo for chicken salad to go with crunchy veges sometimes as a treat. Add in some pine nuts, yummy.

        Louise D. wrote on December 30th, 2009
  27. My first swing at PB and within 10 days of starting, I was off of work and putzing around the house/running errands. The entire day went by, my family came home and was wondering what was for dinner! I had gone about 28 hrs without eating and never even missed it. And I got a lot of stuff done!
    I say first swing because I fell off and got run over by the wagon. Back on it again now and my simple goal is to make it thru today eating primally!
    Thinking I like accidental IFs!

    jenella wrote on December 30th, 2009
  28. I IF as a matter of lifestyle–I don’t like to waste time eating if I don’t have to–but I find that in colder climates (Korea, mid-west) it is hard to keep warm. When I was in Iraq in the summer, I was the only one who didn’t think it was hot and I also didn’t get as thirsty when I was fasted.

    I also spend less money on food, since I’m not eating all the time. I don’t know how this impacts anything, though it hasn’t made me less fit. I think the reduced heat production is evidence of less waste.

    Nick wrote on December 30th, 2009
  29. This is a very timely post for me. Working with a trainer right now who’s got me on a short but hard exercise plan very similar to PB. She has also gotten me to reduce my daily calories to 1600. At first this was hard. She kept saying, “I want to see what this does to your energy”. What I thought she meant was, am I getting enough calories at 1600? It turns out she meant the opposite: are you bouncing off the walls? Once I got good at keeping myself at 1600, I couldn’t fall asleep at night! She said, “Now that is what I’m looking for”!
    She said to me just the other day: “learn to accept a little hunger – not too much, just a little”.

    Katie wrote on December 30th, 2009
    • Just make sure you’re getting enough good food for your body. I like IF because it’s a temporary lull in calories that you can make up for. Skipping meals and eating less than you need triggers the release of adrenaline and cortisol (so does exercise) – that’s what gives you that energy surge. That’s all right for the short term, if you make up for the spent hormones with a good diet. But if you spend very long on a low-calorie diet (for most people 1,600 is low-calorie) then you risk adrenal burnout. At least in my own experience this has been true.

      Elizabeth @ The Nourished Life wrote on December 30th, 2009
  30. I’ve done 10+ mile runs, heavy weight lifting sessions, and 2-hour basketball games all on 12+ hour fast with only water. I experienced no ill effects, and continue to get stronger and faster. I’ve done the eating windows, the Eat-Stop-Eat method, and the alternate day fasting. ESE seems to suit me the best, but I LOVE working out fasted. Eating primaly with plenty of fat helps me go all day, even as long as 36 hours, without much effort.

    Brad wrote on December 30th, 2009
  31. I love this. Years ago, the conventional wisdom said three square meals a days and that’s what I grew up with. I never get hungry between meals if I eat every 5-6 hours and my meals are “clean” (no starchy carbs).

    Jen Nelson wrote on December 30th, 2009
  32. I clicked too fast. I meant to add that I used to fast all the time for a day of too and have done juice fasts in the past and always felt great. I think it’s a great idea and good research!

    Jen Nelson wrote on December 30th, 2009
  33. Strangely enough oats are the only cereal that doesn’t give me the munchies, I can eat a bowl of porridge with fruit and not suffer from hunger pangs for hours. This may be because I am a Scot… 😉

    PS No I’m not eating oats at the moment, I’m trying for the full 30 days free of any cereal.

    PPS I eat 4 times a day, and feel like I have good energy levels, even during this -12C snowy weather.

    Judymac wrote on December 30th, 2009
    • You know, Eat Fat Lose Fat mentioned a woman who experienced less hunger on soaked oatmeal than eggs and bacon (though the book promotes the eggs and bacon!). I would imagine that’s the exception rather than the rule, but it’s interesting to hear someone else had a similar experience. I know it wouldn’t be the case for me!

      Elizabeth @ The Nourished Life wrote on December 30th, 2009
  34. What amazes me is that we, as thinking, rational animals, often fail to examine, consider or even imagine what might have been the natural gustatory patterns of our ancestors, or at least the need for the gut to take a break.

    Even more odd is our insular belief that eating small frequent meals is the right and healthy habit, even though the French and Spaniards hardly ever snack yet don’t suffer the obesity epidemic that continues to grow in our country.

    Johnny at The Lean Saloon wrote on December 30th, 2009
  35. I too am very carb sensitive. I noticed that over a period of two days I seemed to be retaining water. It corresponded with a soup that I made from 3 pounds ground beef and one pound each of green beans, spinach, and carrots. I figured it was probably too carby for me to be having one bowl per day.

    I ditched the soup on the third day and had chicken and olive oil for lunch, and a small handful of almonds for dinner. I didn’t eat until lunch today after that. I felt much better and broke through the weight loss plateau I’d been on. Yay!

    Susan wrote on December 30th, 2009
  36. Anyone have any experience or know of any research about IF while lactating? How does it affect milk production?

    Rachel wrote on December 30th, 2009
    • I don’t know from experience but I thought I’d throw my two cents in. I think it’s most important to be sure you’re getting the proper nutrients in – plenty of saturated fats and fat-soluble vitamins. Think eggs, cheese, butter, meat, coconut oil, etc.

      I really don’t know if IF affects milk production, so I won’t specifically give advice on that part. But unless you hear of a valid reason why not, maybe you could try easing into it? If you’re used to eating three meals a day, try delaying breakfast for an hour and eating normally after that. Then after you get used to it, try eating a really good breakfast and see if it can hold you till dinner. However you do it, just work into it gradually.

      If you feel comfortable and satisfied, if you’re consuming enough healthy food and your milk production stays up it might be all right. But I would really listen to your body to make sure it’s a positive thing.

      I’d certainly love to hear if someone else has personal experience with this, or know someone who does.

      Elizabeth @ The Nourished Life wrote on December 30th, 2009
  37. First off, I love the MDA website and am a big fan. I really want to like the IF/MD lifestyle but have some concerns that I was hoping you could help answer.

    I am an ex-jock and division I two-sport athlete. I have spent much of my life in the gym and at the training table. However, now in my early 30’s, the main reason that I train at this point is for aesthetic purposes (I admit it!) and trying to stay lean and fit. The science behind your concepts do make complete sense. However, at the Olympia this year in Vegas, I met several of the “big wigs” of paleo/crossfit/IF lifestyle who’s stuff I had been just began to read on the internet. After meeting them, I left thinking “I already look better than them doing more traditional stuff.” After meeting several die-hard crossfitters who subscribe to the IF/Paleo diet principals over the past few months…it confirmed what I saw at the Olympia. Most folks out there who are participating in what I would term as non bodybuilding type workouts and diets really do not have impressive physiques….they just look skinny….not fit. Of course, yourself and Arthur Devany are two notable exceptions.

    My wife is an IFBB professional figure competitor and model and eats 6 times a day and does traditional bodybuilding splits and long cardio sessions. She looks fantastic year-round. Everyone that we have ever met in the fitness modeling/ bodybuilding industry eats 6 times a day and includes carbs such as oatmeal,yams, and brown rice into their diet.

    Do you see where I am coming from? I really want to get off the traditonal bodybuilding concepts. The science makes sense but besides a few examples, I don’t see the proof. Help?!

    Jeff Sakamoto wrote on December 30th, 2009
    • I have the same questions as Jeff S.
      I used to be in the Obese category – adopted a bodybuilding lifestlye got down to 9% BF and stayed healthy. I like what IF has to offer and I love the idea of not thinking about food all day but I do get foggy and tired if I go longer than 4-5 hrs without food.
      Can someone speak to Jeff S. concerns?

      Jenn wrote on December 30th, 2009
  38. Sorry to point out that the French now have a rising obesity epidemic. In the five years that we have lived here, we are seeing increased obesity on the streets.

    This corresponds with the huge updrive of junk food now available…all for convenience…

    The original French food pattern in our area was two small meals (breakfast and goute -afternoon tea) and two large meals per day (lunch and dinner).

    Judymac wrote on December 30th, 2009
    • Is the increased obesity with the “native” French people? Or is it the increased immigrant community to France who are the ones who are obese?

      redcatbicycliste wrote on December 31st, 2009
  39. Perhaps I just need to let my body get used to it, but I’m the exact opposite. I’m lethargic until I eat my breakfast, but once I do, I feel a burst of energy.

    Also, while trying to gain weight right now, I doubt I could fit 4000 calories into a tiny window of the day, especially while trying to cut carbs. Over half my calories come from carbs: rice, pasta, and oats. My calories would be less than 2000.

    Allen wrote on December 30th, 2009
    • Hey Allen. I tried I.F. once back when I ate a “standard” diet, and then recently again after I had adjusted to the primal-type of diet that Mark advocates. I found I.F. MUCH easier when eating very low carbohydrate, because my body was more efficient at using fat (dietary, and in my body) for fuel. I was doing 24 hr cycles (ie: eat dinner, breakfast, lunch, then not eat again till the next dinner).

      If your body is expecting to be able to use easily converted carbohydrates, then it’s no wonder you feel lethargic, and then a burst of energy after eating them.

      arlojeremy wrote on December 30th, 2009
  40. I fall into the same trap of overdoing it on the fruits. Also, I find IF much more manageable when I eat a ‘late lunch’ around 3 or so and then fast through the evening and night. When I wake up the next day I actually am quite energetic and usually do a workout, wait an hour or two and then have a nice big breakfast (late around 10 or 11AM).

    Curtis wrote on December 30th, 2009

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