Who Should (and Shouldn’t) Try Fasting?

Last week, my post on the “Myriad Benefits of Intermittent Fasting” opened up a can of worms. In it I discussed how fasting can have a positive impact on human longevity, blood lipids, diet compliance and neurological health to name just a few of the potential health benefits. Naturally, many readers wondered if they’ve been missing the boat on IFing, and whether they should start skipping breakfast, lunch and dinner ASAP. In fact, who needs food anymore when you have IF! Not so fast.

Fasting can be an effective lifestyle hack, but is it right for everyone?

Not exactly. Not always. In other words, no. Let’s take a closer look.

Intermittent fasting is a tool that can be used – or misused – in the pursuit of health. As Keith Norris might put it, it’s something to add to the quiver. A tool to be drawn upon when the time is right. You know what? Let’s extend this archery metaphor, possibly to the breaking point (a skill I’m well-known for). Let’s go ahead and butcher Keith’s neat and tidy and effective metaphor with a look at a fictional monster-hunting archer with a quiver full of specially designed arrows. This monster-hunting archer, if he’s any good at what he does (and I’m going to assume that he is well-versed in classical monster lore, including weak points and monster food allergies and heavy metal sensitivities), is going to pick and choose which arrows – which tools – to draw from the quiver based on the context of the situation. Now, does this archer reach for any old arrow when faced with, say, a vampire? No, he goes for the wood-tipped garlic-laced arrow. He’s not going to waste the silver-tipped arrow on the common henchman (being a soft metal, it might not even pierce the armor, let alone kill the guy). He’ll save it for the werewolf. The metaphor is probably mangled beyond recognition now, but my point (shakily) stands: IF is a tool to be used in the right context. Zombies, for example, are particularly vulnerable to fasting because their satiety hormones are all out of whack.

So what’s the right context for fasting?

You might say that the perfect context for fasting was our ancestral past. Industrial food didn’t exist so metabolic dysfunction wasn’t an issue; “exercise” was either intense and brief and infrequent, or low level and drawn out; stress was acute, rather than chronic; and eating one or two large meals was the natural result of having to hunt and gather. We can’t return to those times, so we do what we can with what we’ve got today. Avoid industrial foods, exercise like you’re a hunter-gatherer, and limit chronic stress by sleeping, sunning, doing things that make you happy, and avoiding things that crush your soul. If you’re doing all these things and feeling like you need a final push to lean out or jumpstart the weight loss after a plateau or explore the myriad benefits listed last week, you’re probably in the right place to be experimenting with intermittent fasting. So – Primal folks who are losing weight or looking to lose a bit more, and getting the right lifestyle changes enacted (sleep, exercise, sex, leisure, rest, relaxation, mental stimulation) should definitely try fasting. They will likely flourish.

What are the wrong contexts for fasting?

An insufficiently Primal Blueprint-based diet. You have to have all your dietary ducks in a row. I recommend that anyone new to IF that wants to incorporate IF should be fully Primal for at least three weeks before trying it. That means getting rid of all excess sugar, grains, legumes, and vegetable oils, all of which conflict with satiety, metabolic function, and insulin signaling. If you are overweight, carbs should also be reduced. If lean, reducing carbs isn’t quite as important. Either way, you should be proficient in drawing upon fat as an energy source (since that’s what you’ll want to be running on during a fast), and those who are overweight or obese are efficient at storing, but not burning, fat. IF can be a good tool for speeding up the fat loss process, but it’s best used to supplement an already-strong eating plan. Once the food is dialed in, fasting will be immensely more beneficial and far less difficult.

You should also be in a good place – mentally, physically, and emotionally. Take stock of the negative and positive aspects of your life. Do the former weigh more heavily on you than the latter? Intermittent fasting may not be right, then. Get those things handled, or put them in proper perspective, and perhaps it will one day. Remember: IF is a type of stressor, and adding any new stressor (however potentially beneficial) to a heap of existing stressors will likely compound the problem. Are you the glass half-full type, the bright eyed optimist fully appreciative of just how green your own grass is? If so, you may be able to handle another stressor in the form of fasting.

You should have cortisol under control. Fasting boosts cortisol, which is not a problem in healthy folks, but in those with cortisol disregulation (think belly fat, think the skinny fat look, lack of sleep, overtraining, chronic cardio, the incessant need for coffee to keep eyes open, persistent low-grade stress) it can be disastrous. If you know you have a cortisol issue (that is, you’re actually monitoring it clinically) or even if you just suspect you do (maybe you notice the creep of belly fat accumulation, more so than in other areas), fasting may not be right for you. Get the problem handled (get more sleep, stop overtraining, stop following politics) and you’ll probably be able to reap the benefits of IF.

There’s also the grey areas. Let’s explore a few of them.

Should pregnant women fast?

There are a few studies that shed some light on the subject, most of them focused on pregnant women fasting for Ramadan. One study found that in pregnant women fasting during Ramadan, placental growth slowed but grew more efficient; fetal development proceeded as normal, but nutrient reserves were limited and there was less room for error. Assuming fasting mom has steady access to nutrients during the pregnancy, the decreased placental reserves shouldn’t be a problem for fetal development. Another study using healthy pregnant women concluded that fasting during Ramadan had no negative effects on fetal development or maternal health. In another study, LDL/HDL ratio decreased, cortisol increased, and fetal health was unaffected during Ramadan, while another found that fasting had little effect on uterine arterial blood flow (which supplies nutrients to the fetus). All in all, though the studies indicate that fasting doesn’t likely pose any danger to the fetus or to the mother, I lean toward no. I mean, why? I’m sure a fifteen hour fast is safe enough, but I’m just not sure it’s necessary or even beneficial during pregnancy. Just eat when you (and your fetus) are hungry.

Should diabetics fast?

I hesitate to make medical recommendations. In fact, I won’t. But I will point you to an interesting account by a guy who “defeated” type 2 diabetes with intermittent fasting. He didn’t call it that – he called it skipping meals – but it amounted to IF. Lee Shurie began by lowering carbs, exercising, and losing weight, which helped but did not cure him. He noticed that his blood glucose was elevated upon waking so, instead of eating immediately and spiking it further, he waited until it dropped to normal levels before eating. Now, this took a while, sometimes until the early evening, but he found that if he ate only when his blood sugar had normalized, it stayed normal all the time. Shurie was effectively IFing without knowing it, and no longer classifies himself as diabetic. Will the same thing work for every diabetic? Maybe, maybe not, but it’s something to consider. IF does generally improve insulin sensitivity, glucose tolerance, and helps with weight loss – all desirable things for a diabetic – but remember that before he was able to skip meals, Shurie had to reduce carbs and start exercising.

Bottom Line?

Bottom line, there is no concrete, objective law regarding the suitability of intermittent fasting for a particular person.

If you’re truly hungry, eat. Failing to do so will add stress.

If you’re stressed, don’t IF. You don’t need another stressor.

If you’re training six days a week, don’t IF. Unless you’re genetically blessed, you’ll need lots of fuel to prevent overtraining.

If you’re not hungry, don’t eat. If coffee’s enough, skip breakfast.

If life is good, try fasting.

In the end, the prudent path is to simply listen to your body. Don’t let CW grazing propaganda drive you to eat when you aren’t hungry; don’t let the IF dogma make you feel guilty about grabbing a handful of macadamia nuts and jerky in between meals when you are. Try it out, skip a meal, go fourteen hours or so (you already do eight every night) without eating, get a workout in, go for a walk, go about your day and see how you feel. A quick trial is not going to kill you. Remember when Primal eating sounded extreme and even dangerous? When the thought of purposefully consuming animal fat seemed sacrilegious? Exactly.

Are you lightheaded?

Are you weak?

Did your workout suffer?

Then maybe it’s not for you. Maybe you need to fix a few things (Primal eating, sleep, chronic stress) and then try again. In a perfect world, we’d all have untouched, undamaged metabolisms with jobs that we love and plenty of leisure time to spend with friends and family, and intermittent fasting would be the default eating method, but it’s not and we don’t.

How has fasting worked for you? How has it not?

TAGS:  hormones

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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154 thoughts on “Who Should (and Shouldn’t) Try Fasting?”

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  1. Good post. Thanks as always for the great information.

    FWIW, there is some raw vegan YouTube video out there that is making the Primal/Paleo blogosphere rounds. The guy accuses Devany of being on steroids and you of being on HGH and only using pictures of yourself from years ago and no longer showing yourself in public. Seems quite defamatory to me.

    1. Do you have a link to one of the videos or a tagline to search for?

      1. Yeah, the guy who posted the video is known TheRawVoice on YouTube, if memory serves. He has posted quite a few defamatory comments, in my opinion.

      2. youtube.com/watch?v=8L10cNeABbA

        I’m the guy arguing with idiots in the comments section. I feel like Reggie Jackson in a slow pitch softball game. Their comments are so feeble-minded or just plain lies that its easy to swat them out of the park.

        1. I watched 5 videos by this young man. He sure likes to neglect basic debate logic. He attacks individuals personally with differing opinion, not the actual point! So maddening! Oh well, I got to get back to my bacon.

        2. Ha Dave! I was lovin’ your comments over there. Great analogy too.

        3. It’s all been entertaining in a maddening sort of way. The video is supposed to slam Paleo gurus for being fat, but when I called him out on not showing any pictures of Mark or even mentioning Art De Vany he responds that Mark is a weakling and Art uses steroids. But the point of the video is that Paleo gurus get fat. To an emaciated vegan I suppose Cordain might look slightly overweight, but I thought it was a stretch. Then he goes after people not even in the Paleo movement like Taubes and Dr. Kendrick. They teach a very important lesson though. If Paleo ever becomes as dogmatic and as ideological as the Vegan movement, I’m outta here.

        4. Its Harley “durianrider” Johnstone that are running the “TheRawvoice”.

          Really annoying vegan guy :\

        5. “First they ignore you, then they laugh at you, then they fight you, then you win.”

    2. This guy is a complete tool. He hates everyone that doesn’t attempt to OD on bananas every single day. He even trolls raw vegans. lol

      1. He shouldn’t be able to make those statements and get away with it. DeVany and Mark could potentially have their reputations harmed by this guy’s BS.

      2. He is a dick head Aussie. He put up a picture of Taubes on his blog pointing to his belly. I’m an Aussie so embarrassed by this idiot.

      3. Ugh, this guy. There are many people in the vegan community that, while I disagree with their viewpoints, I still have a lot of respect for. Durianrider is enough of an aggressive conspiracy theory nuisance that even the raw vegan community GiveItToMeRaw gave him the boot a few years ago. https://www.giveittomeraw.com/forum/topics/removal-notice-durian-rider?id=1407416:Topic:1036626&page=1#comments

        I hate to hear that he’s taking jabs at Mark’s reputation though, especially the bit about how supposedly commercialized Primal is. There’s products for sale here for sure, but a) there’s also a freaking EPIC amount of free information and an also amazing free community and b) I find that product promotion here is overall pretty tasteful. Meanwhile, 30 Banana’s seems to have just as much for sale, including a 97$ ebook(!). Having been a member of both the vegan community and now the Primal community, it seems pretty clear to me that I want to be where the people are friendly and the vehement dogma is low; that would be here.

  2. Another good write up Mark. I am in the opposite boat now that I have been doing Primal and IF for a good 3 months now. I usually IF for 16-18 hours and eat 2 or 3 meals in the late afternoon and evening. Sometimes I’ll skip a whole day too.
    *If* I eat breakfast I feel hungry all day long and can’t concentrate on anything except how much I want to eat. My workouts are much better since doing them fasted and I have lost no (none I tell you) strength.
    IF works for me and I hope more people who are “afraid” to try it just give it a shot.

    1. I fast 16 hours a day and love it. In fact, I’ve added significant muscle and strength while eating this way… and, I’m an endurance athlete, to boot. It’s not an approach I recommend to everyone, but it can work very, very well. If anyone wants to know more, check out http://www.leangains.com... Martin Berkhan runs an excellent website.

  3. I know I fasted in my first trimester but it was definitely NOT something I chose to do!

  4. I can’t believe those with a history of eating disorders weren’t mentioned. IF can be extremely triggering even if you’ve recovered from the eating disorder and it’s no longer a “stressor” in your life.

    1. agree – I was really disappointed Mark didn’t even mention this. I for one posted on his last thread about IF saying this.
      Makes me feel somehow trivial.
      Having said that, I don’t eat til lunchtime cos I don’t get hungry – but call it IFing and my brain goes weird on me and I get cravings.

    2. I agree completely — and the omission is pretty common. I haven’t seen any blog posts about IF that mention people with a history of eating disorders. Has anyone else? (I don’t claim to have seen all blogs…)

      1. I’ve posted in several threads (as well as my own journal) on the forums about it!!!! recently – following Marks article perhaps – there was a glut of people wanting to start IF about 10 days after startuing PB because they had “stalled”. It was like a fad. I voiced over and over again about the ED thing.

        BUT I guess we are still a small part of the overall community. Many more people, even with disordered eating and relationships with food, do not consider they have an ED or see the way this might be part of their problem.

        First time I have felt a bit “put out” at Mark:)

        1. Denise… I don’t like to call it IF either. I am just a paleo newbie, but the switch was very easy for me to flip, once I made up my mind. I don’t have an eating disorder, but an addictive personality instead.
          So, learning to eat only when hungry was an awesome revelation for me! I didn’t have breakfast this morning, and did not sweat the fact that I didn’t have time for lunch until about 1:30 this afternoon.

        2. I turned my eating disorder into a positive thing. I was very good after my children were born, but a few years later felt it creeping back in. An 8 day water fast cured me of that, and IF’s when I feel the need over the past few years have been wonderful. I’m so far removed from that now, I never think about it. IFing is not a trigger, for me at least. It was part of my recovery. I want to be strong, I want to be healthy, and maybe it’s crazy or maybe it’s evolutionary that I sometimes want to be hungry. Pointing to the known benefits IFing and the known benefits of increased mental performance while slightly hungry, I’m going to say it’s evolutionary.

      2. Maybe these comments can serve as a blanket “If you have an eating disorder you might want to consider not fasting” disclaimer.

        1. The article is title “Who Should (and Shouldn’t Try Fasting?” so I would think those with either an active eating disorder or history of eating disorders could warrant a section (just like pregnant women, diabetics, etc. do).

          The question “should people with eating disoders fast?” is a tricky one. Some claim it cures compulsive overeating, for instance. I would like to see this question addressed in more depth.

          Another interesting topic could be “When does paleo eating turn into disordered eating?” Again, a tricky one.

        2. ok – then the whole thread can stop now as “IF is quite good for some people sometimes covers it all???

          Not being funny – but that just feels like you are “shutting people down”. Maybe you weren’t – in which case I apologise.

          And I think Gazelle has an interesting point – when are any of us getting “disordered” in our eating behaviours. Semantics maybe? But there’s room for all these comments….well, except for some of the really offensive ones:)

        3. Gazelle, that would definitely be an interesting article (“When does paleo eating become disordered eating”). And as Mark points out below, the whole area deserves its own post (one I hope he is able to follow up with soon!)

          I have never had an eating disorder in the sense of anorexia, bulemia, overeating, etc. But I am QUITE rigid when adhering to a diet plan. She has frequently referred to my primal lifestyle choices as “obsessive” (e.g. trying to find flat shoes, or experimenting at not using shampoo). But I get special criticism for being “difficult” when we go out to eat with friends. I will try to just choose fasting but am told that is “weird” and “anti-social.”

          I don’t feel like it’s disordered or that I am hurting anyone, but perhaps she has a point and I am too extreme?

        4. Don’t feel bad if fasting doesn’t work for you. I am recovering from an eating disorder/veganism/depression–hard to know which came first, but none helped the others, that’s for sure. Thought with ten years recovery I could try the 16 hour IF program. Nope. Skipped breakfast and by 10AM I was ready to cry or hit somebody. I remember that horrible mental state only too well. Eating a meal only helped about 50 percent. The afternoon was spent trying to decide whether to go to sleep or die. Some of you know exactly what I’m talking about. If you don’t, count yourself lucky. Julia Ross, in The Mood Cure, talks about how even a few hours of low serotonin can trigger a relapse in the eating disordered. Don’t need to go there, just need to eat three solid chunks of protein and fat every day. I knew that, but decided to try IF anyway. Guess I learned my lesson. Fasting is NOT for everyone.

      3. As Gazelle and others have pointed out, the topic of eating disorders on the whole, and as it relates to fasting in particular, deserves some broader coverage, and special care and attention; not just a paragraph or a few sentences. I’ll see about addressing this topic in the future. For now, though, yes, if you have an eating disorder, first, speak with your doctor, and second, keep in mind the spirit of this post: it’s important to dial in a healthy eating pattern before even considering fasting.

        1. sorry Mark, “first talk to your doctor” did make me smile. As they know so little about nutrition in general what on earth makes you think they would know what to do with an ED?? My GP is great, but any diet advice she ever gave was pure CW. The other tool in the arsenal – anti depressants. I once rang the Uks official ‘helpline” to see what help there was for me. I abbreviate… I asked for help (in tears) they asked if I was willing to stay the weight I currently was, I said no (240lbs) they said “can’t help you”. End of call – next 15 years of pain til found primal and paleo.
          My eating pattern is finally feeling healthy – has been for a few months now. BRILLIANT – but iF still somehow rankles my thought processes.

          Maybe other people have better experiences with the medical profession, maybe I was unlucky – and i also understand you have to “cover yourself”:)

          Meanwhile – I eat when I’m hungry now and if thats 18 hours after my last meal – so be it. BUT I won’t call it IF and I won’t let myself get sucked into “if 16 hours is good – maybe next I’ll do 24/36, cos it has to be even better”.

          Thanks for the post though – always thought provoking – and at least i feel heard here!

  5. Do you think it’s strange you are modeling your nutrition after people who rarely lived past 40?

    1. Who are you asking this of and is this the most appropriate place to launch into such a contentious discussion, Fred?

    2. Not due to heart attacks, due to animal attacks. We don’t have to fight lions for our meat.

    3. Did it ever occur to you that infant mortality plays a huge factor in average life expectancy? In 1900 average life expectancy was 47 but there were plenty of people who lived into their 70s and 80s (and beyond). A simple statistics class might be in order.

    4. Really? Please don’t bring your lack of critical reasoning skills to a place where only the enlightened are welcome. Bad move and worse question.

      1. “…a place where only the enlightened are welcome”? how is one supposed to become enlightened, unless they come and read and — perhaps — ask “dumb” questions from time to time?

        1. Well… you are right. Perhaps I go about things the wrong way sometimes. I assumed someone would look into the subject before asking that particular question to this particular community. No problem with “dumb” questions at all, they’re needed. My instincts led me to believe it wasn’t exactly innocent by any means.

      1. We, the primal supporters, aren’t dogmatic nor narrow minded nor insecure about our beliefs… are we?

        I mean, this site is open to public discussion. And I do think the question was pertinent enough.

  6. Mark, thanks for additional coverage of this very interesting topic. I’ve been eating primal for about 2 months now and am “in a good place,” as you say. I’m currently in the middle of my first ever fast, starting with 24 hours.

    The biggest difference for me is the type of hunger I experience. Before it was a panicked, “must.eat.NOW!” feeling whereas now it’s more of a low, calm sensation. I’m more aware of my body’s needs, but not controlled by them like a junkie..

    Your book and the writings on the site are an invaluable resource, please keep up the good work 🙂

  7. I love it! Straight up! Great post Mark.

    I’m one of those people who can get 2000 calories in a single sitting though, so it makes it easier to fast. I feel fantastic when I fast! And sometimes just the thought of breakfast disgusts me.

    I typically go 12-16 hours every day (think dinner to brunch or lunch), and once a week or so its closer to 24 hours (think dinner to dinner).

    Its not for everybody, and definitely not for everyday, but I pull the arrow when I need it, and only when it feels good!

  8. I always work out fasted, and for the first time since I was 9 I can see my abs. No loss of strength.

    @Fred: my father died of an acute MI two weeks before his 52nd birthday. The best advice I got back then was from a fraternity brother, who said, “The moral of the story is, don’t get fat. Don’t be offended.” I wasn’t. However, easier said than done, especially if you eat “heart healthy”.

    Thanks to primal/paleo eating, training and “chilling”, I have never looked or felt better. Don’t forget that when they say that “people didn’t live past 40”, they average all mortality (including that of infants), so that if you did make it to 40, you could look forward to many years of vigorous health.

    1. The fasted workout is the number one thing I’ve learned since going Primal. My regular resistance work is done on a 12-15 hour fast, and I’ve had pretty consistently good results. On a 24 hour fast, I can get through the workout, but it probably won’t be my best. But for all exercise, including races/competitions, I love going in with a real hunger in my gut; I feel capable, motivated, light, and ready!

  9. Since I’ve been eating “primally”, I’ve found that IF’ing comes somewhat naturally. Some days, I eat starting in the morning with my coffee – and I’m fine. Other days, I am not hungry until after noon – and I’m okay with that too. I just eat when I feel the need to eat. What a change for me!

    1. My only issue with IF is this.Though I am often not hungry until after noon, my work environment is like a prison for the obese. I find that by the time I am hungry, at say 1:00, someone has layed out Girl Scout cookies and pie. I would rather avoid the temptation by not getting hungry.

  10. Curious here… Lately I’ve been eating the bulk of my calories/protein/fat from about 11am-4pm, but won’t eat anything but plain raw/steamed/boiled vegetables after that, occasionally a small piece of fruit. Does this essentially “break the fast”? Or just a replica of one of those trendy vegetable/fruit fasts?

  11. I appreciate the excellent Dungeons and Dragon style metaphors. Mm, delicious garlic arrows…

  12. I usually skip my next meal after going out to eat or if I eat a bit too much. That way it all kind of balances out.

  13. IF’ing a la Leangains (16/8 fasting/feeding, respectively — skipping breakfast, basically) has really helped me out in the last 6-8 weeks. That said, I didn’t start doing it until being a good two months into being Primal. Any IF’ing I did prior to that occurred organically, so to speak.

    I think you took the right approach to this, Mark, and that approach is the same you take throughout the PB: If it feels right and there are no aggravating factors, give it a shot; if you’re hungry eat; if you’re sore, stop training til you feel better; if you’re tired, sleep; etc.

    There’s never a single right answer and everyone responds to changes to their bodies differently. I agree that people shouldn’t be too quick to rush into IF’ing.

  14. On the forums, I see posts from people who consider a fast after eating the wrong stuff. They view it as “fixer” to offset the damage done and/or as a punishment for their transgressions. Either way, using IF that way seems unhealthy….the double stressor of bingeing followed by starving, and the emotional rollercoaster of using food/no-food as reward/punishment. I wish people would be kinder to their bodies.

  15. I found fasting for 24 hours to simply result in a huge binge and loss of control over my diet with the post-fast meal. However, I can happily do 16-18 hours with no ill-effects and do it regularly. Listening to your own personal signals is imperative.

    1. That’s totally me too, Allison. I get grouchy after about 20 hours, and then go nuts when mealtime finally does come.

      Pretty sure legumes and cheese may be sabotaging my success at this point.

  16. Great post Mark! Before I became pregnant, I used to do 2 dinner-to-dinner fasts a week but after I got pregnant, it was usually about 15-16 hours, unintentionally though, as I would end up skipping breakfast most of the time due to lack of time. Now that I’m breast-feeding, I usually don’t IF (CW creeping up?) although I find myself being able to go for long stretches w/o eating. What’s your opinion on IFing while BFing?

    1. I breastfed all three of my children, all for a full year (of course they started solids as well when they were ready, between 4-5 months). The one thing I noticed is that I was never hungry, although I was more thirsty than I ever thought possible! So I used the opportunity to not only tackle the baby weight but also look closely at what I was eating and how it affected my child. Dairy was ABSOLUTELY off the menu for all three. In the end, all three were, and remain, extremely healthy, energetic, smart etc. So I see no need to worry about CW just because you’re breastfeeding; just make sure you take any necessary supplements so you don’t hurt your own health while losing all the weight. Enjoy your baby! I’m jealous!! 🙂

      1. Thanks Sara! Why were you off dairy, was it affecting them or was it because you were primal? I try to go off dairy but succumb to my morning cup of coffee 🙁

        1. Yes, I was off dairy for the sake of the babies. About 3-4 days after having my first child, I decided to splurge on a chocolate-chip cookie dough Blizzard from Dairy Queen. It tasted awesome…but my baby cried on end for days. I thought it might be a fluke, but I watched what I ate anyway, and sure enough, anything dairy did the same thing to my son. So from then on, I avoided it while pregnant or breastfeeding. I don’t think I would worry about your coffee cream, your sanity is more important than any affect a tablespoon of cream may have! By the way, kudos on breastfeeding; next to giving birth, you are giving your child the most important first step to healthy nutrition. I wish my other soy-feeding forumla mother friends would follow your footsteps.

    2. I found when I was breast feeding, I could go long stretches without eating, but I tended to lose weight too quickly,(3-4lbs in a week) i changed my habits to little nibbles while feeding the baby which helped me to lose weight still and make sure I was providing enough for the baby without too much loss from my own needs. Even after I stopped breast feeding I tended towards loss of weight during any fasting ( was not prone to bingeing ) but after the third kid fasting was only option to keeping any weight off, seemed that my body decided I was going to save up for more kids lol. I still IF without thinking too much on it which I am least maintaining weight not gaining thankfully. My kids range from one whom fasting is just not an option unless you want a temperamental hellion on your hands the other two they just sort of flow with it as food comes. Fasting did help me keep in touch with my hunger signals, and how much or what food I needed. If I go the refrigerator hungry but nothing is appetizing I just don’t eat. Usually though I seriously only want something salty when I fast because I can’t “find” anything to eat.

  17. I fast 16 hours a day at the moment, no problems, just find I can’t train if I am hungry, so have train at the right time. I am thinking of doing cyclic carb loading on weekends to test.

  18. Fasting has grown so popular in the last few months I wonder if you can call it a ‘fad diet’? I see it every where now!
    I do fast or skip meals a few meals in a week it’s an easy way to keep my weight under control.
    But I think my overall health is OK to do it.
    I wouldn’t recommend fasting to anyone who has a medical condition( diabetes), pregnant or recovering from injury .. it can makes things worse.
    Also I think the other extreme is fasting can start developing negative association to food which is not healthy either.
    But as a weight loss tool yep it works but bottom line all you are doing is eating less in the week .. there are other ways to achieve that if you want to!

  19. Great post…. yet again snaps me out of the idea that I have to be like everyone else! I have a pretty speedy metabolism so I get hungry pretty regularly. I typically get up at 5am and eat my first meal at around 8am, and my last meal at 6 or 7pm… with a lunch and two snacks in between. The point for me is more to get used to eating healthy rather than skipping a meal.

  20. i fast 3 times a week; play, exercise 6-7 days a week; some hard some easy..at the end of fasting i do sprints and some play..i feel so light and energic..

  21. I like training in the morning, fasted, unless it’s a long bike ride in which case I’ll eat a big breakfast first.

    I find that I’ve gravitated to fast from bedtime till lunchtime and then eat two meals before sleeping again. However, some days I wake up and feel hungry, so I eat! Simples.

    Yes, Gazelle, for eating disordered (recovered or not) IF is a sensitive subject. I was eating disordered through athletics and I have to watch that I don’t drift that way again when watching the scales … I really should throw them away. Today I was my heaviest in a decade but I’m my strongest and probably ‘besting looking in a bikini’ in a decade too LOL! I even took the pictures at the weekend to remind myself!

  22. eat when hungry, if it happens to take 16-20 hours before you’re hungry then you just participated in IF.

  23. Is there any research on, or women who have successfully done IF while breastfeeding? I successfully used IF before pregnancy and wondering if I can continue while nursing. This question definitely comes from my lack of knowledge on actually where breast milk is produced from, daily caloric intake or fat stores?

    1. Both, think Grok’s time, food wouldn’t always be available, that’s what fat stores are for but they only work well in a low carb environment, or at least within a proper metabolism that isn’t chronically overloaded with carb induced insulin.

    1. I too have considered myself a hard gainer in the past. Eating paleo and cycling between Lean Gains, 531, and Starting Strength for training protocols has given me great results and changed my opinion. I have naturally come into my own and now feel great being a lean, strong as hell, near 40 male. IF with the Lean Gains approach really dialed it in for me. Fasted training takes everything to another level for me.

  24. I’m a type 2 diabetic and I fast all the time in the mornings. The only thing to watch out for is what medication you’re on, or what size shots of insulin you may be taking to make sure you don’t go low.

    I routinely fast from about 8pm to 12pm with no problem. Thats 16 hours. I usually tend to try this when my fasting blood glucose is higher, but I’ve never had issues.

    The best side effect this has had for me is the ability to recognize my hunger and control it, not let it convince me to eat something stupid.

  25. I’ve been doing the primal thing for about 1.5 years and have lost quite a bit of weight. I tend to be bad about it on weekends though and still have a bit of belly fat I’d like to lose. I’d say about 10 pounds. I’ve been doing IF for awhile and seem to have no problems with it. Should I stop because I still have some belly fat?

  26. Am I the only one in the world who would rather skip dinner? I get up at 4:30 and generally eat breakfast around 6 (meat and veggies usually). If I skip breakfast I usually become ravenous by 8. It’s not that hard for me to come home from work and skip dinner though. Most weekdays it’s the norm. I would assume there is no advantage one way or the other as long as the eating window is about 8 hours, but I just find it interesting everyone skips breakfast.

    1. whatever “works’ for you. You don’t get hungry for dinner but you do for breakfast. Sounds fine to me. I also skip breakfast because first thing in the morning is when I workout – can’t eat before as it makes me sick – so naturally end up with 1st meal at lunchtime. Doesn’t affect quality of workout – so works for me. No “rule” just what works and you are comfortable with.
      BUT to reiterate my ED point – I skip a meal cos I don’t want it – but never call it IF even to myself.

    2. funny how we all differ – i have never – since childhood, been able to eat within 2-4 hours of getting up – makes me literally sick (usually) – and so my habit became nothing but coffee/tea in the morning til a very late breakfast or lunch – then i realized – i was fasting! if i dinner at 7 and don’t eat lunch till 12 the next day – that’s basically a daily fast and i “break” my “fast” with lunch some 15 hours or so later–
      works for me!

    3. I eat in the AM, maybe as late as 12 or 1, and then thats it. I’m like you.

    4. In Eat Stop Eat Polin says that he finds a 2 pm to 2 pm fast to be the easiest, and I would tend to agree. You’re asleep during the middle of it, and the end falls during breakfast time, a period where many people simply aren’t hungry.

      Personally, I don’t do a lunch to lunch fast because it’s just not practical for my current schedule, but for 24 hour fasts I think lunch to lunch might be psychologically easiest for beginners.

    5. I was just wondering this myself. I am starving in the mornings too but can easily skip dinner.
      I guess the main issue is the benefits one gets from working out fasted. I’m not going to start working out at night-time to get those benefits. Maybe I need to start working out as soon as I wake up and then have breakfast soon after?

  27. I was quite ill last year and on a long waiting list for surgery (Canada’s great medical system). The MO was take painkillers in the meantime. I was fasting simply because 1. I was either in too much pain, or 2. the meds made me too sick to eat.

    Obviously I lost a good deal of weight, even without exercise. I could barely walk the 1/2 block from the corner to my house with the dog. After I had surgery, I had an enormous amount of energy. Because my stomach was used to not getting food, I continued with the very light meals and IF, even though I was no longer in pain or experiencing nausea.

    I find that when I eat too much I feel absolutely horrible. I’ll do a few days when I eat very small meals and also skip some meals. In no time I feel better again.

    I’m certain that occasional fasting is not a bad thing. It allows our GI time to dispose of junk that’s accumulated and heal itself if we’ve eaten something that doesn’t quite agree. At least that’s my take on it. I suffer from IBS and have Celiac.

    When I was a teenager I used to go days without eating anything, just having water. I felt great. I was in shape, I could jog, do sports in school. I was never underweight or overweight. I had loads of energy. My parents thought I was sick. They would drag me to see the doctor all the time. But I never felt weak or ill. And even the doctor said that as long as there are no signs of illness or disease there is nothing wrong with what I was doing.

  28. My question is related to the proposed health benefits of IF. Is there anyone who has used it and has noted an anti-inflammatory response or the correction of any other condition like high blood pressure?

    I have been enjoying IFing for two 24 hr. stretches each week. Sure, I would still love to lose weight but my goal now is to create the best support for my health. I have family members with hashimoto’s thyroiditis and hypercholesterolemia so anything anti-inflammatory seems positive to me!


  29. So whats more important? Holding to
    your 18/6 IF, or fasting 12 hours
    before strength training? My eat
    window is noon until 6pm.

    It seems impossible to do both if
    you are doing your strength training
    in the evening. The only reason it
    works for me now is because I’m only
    working 3 days a week and doing
    morning workouts. If I where to go
    back full time there would be no
    way for me to do my current 18/6,
    and enter my workout 12hrs fasted.
    I suppose I could cut back to a 6hr
    fasted pre-workout, but that would
    still put me outside my 18/6 IF by
    the time I get home from work.

    Don’t you see, this turns into scheduling, and Grok didn’t live
    by this yoke. I’m very adamant
    about a 12 fasted workoutAND my
    18/6. Any thought?

    1. I think a good fasting period is more important than a lengthy pre-workout fast.

      If I were you I’d maybe move lunch an hour later, an dinner two hours later. That way you could workout before dinner in a 6-7 hour fasted state and still preserve a 17-18 hour fast between dinner and lunch.

      That’s just based off of my personal experience though, your mileage may vary.

  30. I used to eat an extremely high whole grain, low fat diet. I have always been thin, and I felt the need to eat every 2 hours or else I would feel shaky and weak. I never thought I would be able to fast.

    After slowly transitioning to a (mostly) primal diet over the last 3 months, I realized it usually takes 6 hours before I even start to feel hungry after breakfast! I am not sure if IF is for me because I am generally under a lot of stress as a law student, but I was intrigued by the idea so I decided to give IF a shot today by skipping lunch. So far, so good… I am far more alert in my classes than I ever was before switching to a primal diet, and today has been no exception (I used to fight myself to not fall asleep in every class). OK, back to studying! 🙂

    1. Great, just what the world needs. Another lawyer.

      JUST KIDDING. I’m in my 19th year of practice. In a few years, you’re going to look back at law school as the glory days.

      Anyway, what you wrote about hunger and how your relationship with food has changed since the big switch really resonates with me. I followed a vegan diet beforehand and was seemingly always really hungry. Not any more.

  31. Megan,

    When I was breastfeeding, I noticed a quick drop in milk supply whenever I got too busy to eat. Eating more calories and hanging out with the baby always brought it right back.

    Basically, when you’re preggers, your body acts like the baby is more important than you are;it’ll eat itself, if necessary, to keep baby healthy. Afterwards it’s a different story. Your body treats milk-making like an expensive luxury: in a crunch situation, the milk is the first to go.

    All of this is a long way of saying, probably IFing will make your supply drop temporarily. On the other hand, if you’re primal already and you’ve got no problem with your supply, you could try it and see what happened. It should bounce right back anyway.

    I wasn’t primal at the time, but I did an allergy elimination diet that had me off legumes, dairy, and all grains but rice. So your mileage may vary!

    1. if I try to fast/don’t eat enough while breastfeeding, I notice a drop off in milk supply as well as an increase in crankiness! :-p lack of sleep + lack of food = rawr!

      doesn’t help that my baby girl is 17lbs at 4mos of age. oh well, more bacon for me!

      however i am losing about 1lb a week since going almost completely pb 🙂

  32. I love me some IF, which is ironic, since I’m a serious cook and I also love food. For me, though, the bottom line is this: I used to be hypoglycemic…REALLY hypoglycemic. I’m a very active and athletic person, and before adopting a Primal lifestyle, my energy needs caused me to eat a lot of grains, my insulin got out of control, and I found myself feeling faint if I didn’t eat every two or three hours. So, for me, the beauty of IF is simply that I can do it. I love the empowered feeling I get each week on my fasting day when I think to myself “A year ago, this would have been functionally impossible for me to do.” Now, though, fasting is easy, and that little high of achievement is hard to beat.

    1. I had the same issue. Before switching to primal eating, I was SO hypoglycemic I couldn’t work jobs that didn’t allow me small breaks to have a snack every few hours. Now I can easily go without food for extended periods of time and feel absolutely fine.

  33. Wonderful post, full of nice common sense (in the good sense of the word!), no ideology, no dogma. I really enjoy reading such wonderfully informative and encouraging posts. Thanks a lot Mark!

  34. Excellent post. I,in fact completed some research and did my first IF on Monday. The 16/8 split as advocated in Leangains also fit my schedule the best so that is the model I followed. I skipped breakfast and avoided calories till early afternoon. It was surprisingly easy….probably(in part) due to following a primal WOE.Over the last year I found myself clinging to the “grazing” concept and eating by the clock and not necessarily for hunger. It was then that I discovered IFing and another (supposedly) dietary “truth” was chucked in the dust bin.

    I was curious about frequency. My initial plan is to follow a 16/8 split twice weekly on my usual recovery days(Monday and Friday).

    Keep up the great work!

  35. I always understand things better when described with the zombie models 🙂

    and, I’m another one that has coffee in the am & then something around 10 or so followed by an afternoon something. Dinner is skipped most nights – not hungry.

  36. Whilst I am a huge advocated for IF, I can easily see where negative food associations can become quite ‘obsessive’ for the minority.
    As Mark says, make sure you have everything ‘else’ in check before you attempt to throw something else into the mix.

  37. Did anyone see Dr.Oz today? It was about the HCG diet. I am fuming over this episode. This type of diet will NEVER be the answer to the obesity epidemic. To feature it on a high profile show like this seems ridiculous to me. What a load of bull. Urgh!

    1. Dr Oz is USUALLY ridiculous and shoveling boatloads of bull! He’s a SUPERB cardiac surgeon — if only we could confine him to the surgical suite! He’s ‘expanded’ his view of himself as a miracle worker (which, apparently he is: IN CARDIAC SURGERY!!) into seeing himself as the god of all-things-medical! Alas, it’s a common problem for docs… His personality (and his good personal genetics) — and the draw of fame — has turned him into a fool.

      1. I usually don’t jump to the defense of any TV doctor, but I saw the episode in question, and I must point out that Dr. Oz said he would NOT recommend anyone follow the HCG diet. While he does follow and endorse CW in eating/exercising, etc., what is really frightening is the impact this show has on a large percentage of the population. It’s like people need someone else to “think” for them, because if a doctor endorses it, well it must be be the right thing to do. Critical thinking skills have fallen by the wayside. I am very glad to have wisened up and developed those critical thinking skills and no longer follow the “expert” advise of any TV doc (or, really even my own GP)…always think first, is this beneficial for me and my body?

  38. I find my IF’s are usually on the low side, maybe 14 hours or so after dinner. I do occasionally pull a 16 hour, but mostly for the ancillary benefits beyond fat loss since the PB took care of that problem area fairly quickly 🙂

  39. wow I happened to do a 16 hour IF today.. Felt great and I enjoyed my light lunch. Will be doing a 24 hour one soon. I like the idea of a 2pm to 2pm.

  40. Because I work in the restaurant industry, we keep odd hours already! Its actually humorous to see the staff enjoying dinner at midnight! Therefore, if I get home at 1 or 2 AM, there is NO WAY that I have an interest in food in the morning. My husband will comment on my “noisy” tummy in the morning and tell me to “eat already!” but I know my tumm tumm is just finishing up digesting whatever I consumed the night before.
    I have always enjoyed fasting, and now I just eat when I am hungry. Sometimes I go from dinner (late night) to dinner on off days (normal dinnertime)..I usually have a few days off in a row, and if I want breakfast I enjoy it, although it is usually at “lunchtime”
    I dont get technical about it, in fact I dont even think about it. Why would I want to shove food down the gullet if I wasn’t actually hungry? I have been on this path for awhile I guess, Hubby still eats when its “time”! (He is a 300 lb sugar addict!);)

  41. And to all the preggo and BFing ladies out there, I was ravenously hungry during pregnancy and nursing..I also gave up dairy while nursing, gastro baby distress..it was an immediate relief for both of us!
    I had not gone Primal or paleo yet, so I am sure my body would have responded differently…I will never know! Ha ha
    I ate when I was hungry,(gained 50lbs, both kids, I am a healthy weight at 5’1″)My Doc was in a panic over my weight gain!I drank lots of fluids and made enough milk to keep the freezer stocked! Lost all the baby weight in 4 months for both kids, but had zero sex drive while nursing (way out of the norm for me!)
    Bottom line..Do what feels right for you! (as long as your thinking isn’t clouded by “should’s and shouldn’ts”)

  42. I started IF (sort of) when i started eating primal- i would eat twice a day instead of 3 or 4 times- no window i used to jsut mix it up (either breaky and dinner or lunch and dinner ect). I lost 2kg a week and had loads of energy. After 2 weeks I started eating three or four meals a day again (primal) and had a weight loss stall and had less energy. (partly due to the large nut intake).

    Now that im back doing IF (no breakfast usually) My weight loss has started back up and energy levels and feelings of happiness has returned. I’m going to stick with two meals a day for good and i still eat the same amount i did when eating 3-4 times a day.

    For me IF seems to be essential to weight loss, energy and happiness levels. But i dont use it as a tool to eat less- i just eat less often.

  43. I’ve never been a breakfast person, so I’m relieved to find IF! 🙂 Being overweight, I always thought not eating breakfast contributed to it. Now, it seems that all that grain I was eating was what contributed to it. Since going primal, I’ve lost 8 inches off my body. I eat breakfast when I wake up hungry, when I’m not hungry, I wait til lunch. It’s all good. 🙂

  44. I think I’m somewhat of a natural IFer. My life is such that sometimes I just don’t get around to eating until ‘later’. Sometimes much later. My body pretty much handles it without complaint. I find it slight;y harder when I have a plan for IFing rather than it just being something that happens. Maybe just because I am more mentally fixated on food.

  45. Coming from someone who has had an eating disorder..I find that eating primally has helped the most of any treatment.
    Eating fat and protein eases my mind. Carbs are the worst, and if I eat too many of them, that is the most triggering thing.
    Sometimes I will skip breakfast simply because I don’t have time to eat in the AM before work (which is about an 18hr fast), but I will still eat enough at lunch and dinner so that I don’t lose weight (I wouldn’t want to lose any weight anyway) which is easy with enough meat and fat.
    Can honestly say red meat has saved my life.
    On primal I simply don’t want to starve.


  46. I’ve been “if”ing for about two months. I have been primal about two years (with one relapse during a three-week holiday). Typically, I eat around 1:00 for my first meal (up at 7:30) and eat dinner around 7 (bed at 10:30). Sometimes I will munch on light snacks during the day, but not often. My morning is a coffee with heavy cream. So far, I have more energy and have “converted” more fat to muscle. I’m excited to continue this and find my sweet spot balance between food and energy…

  47. I tried (intentional) IFing for the first time last week, inspired by Mark’s blog post. Since then, I’ve done one 24-hour fast and three 16- to 18-hr fasts. I’ve been amazed at how easy it’s been! My hunger has been minimal or nonexistent the whole time. Which makes me wonder… how often had I been eating previously, when I wasn’t hungry?

    Although I’ve been eating mostly primal for a long time, I still have a lot of excess abdominal weight & am prediabetic, and I know that Mark mentions above that that makes me not a good candidate for IFing… but from my experience in the past week, I’ve not been hungry, not had any sort of dizzyness or other indicators of problems, and have had a noticeable increase in energy. (I’ve been a lifelong morning slug — even after 10-12 hours of sleep, I can barely rouse myself in the morning! But while IFing, I can wake early and with lots of energy, for the first time ever…) I also notice how much better food tastes, each time I come off a fast.

    From the first skipped meal, I could feel my midsection shrinking, and I’ve lost a belt notch already. IF is addictive… I find myself having to convince myself to eat now…

  48. I have to agree with you Mark. The key to any of this is being in tune with our bodies. Only by truly listening to the messages our incredible bodies are sending us can we really know when to fast and the potential repercussions it may have.

  49. When i was a teenager i never ate breakfast. First meal of the day was lunch. Sometimes had an afternoon snack once home from school, then out to the local park to play (usually basketball) for a couple of hours or so. Home for dinner around six-ish. Never had energy lows during the day, despite being a “growing boy”.
    Only started eating breakfast in my early to mid twenties “because it’s the most important meal of the day”. Load up on those breakfast cereals/toast etc and ended up feeling hungry by 10am?.

    Watched a british tv show last year, where the two people in it spent one week eating the “diets” of the ages (1500’s, 1600’s, 1700’s, 1800’s etc). Only the rich were eating three meals a day. It wasn’t until the late 1800’s where “the poor people” started to eat breakfast as they could now afford it.

  50. It’s interesting to read this article today, given that yesterday after a lengthy discussion with my personal trainer, she advised that I stop my 2 day a week intermittent fasting until I get my low carb eating happening consistently.
    When I first read about IF I thought it would be a sure thing 1kg weightloss per week. It hasn’t been so I’ll go with this advice and get the primal eating under control first.

  51. Thanks for putting this out there, Mark. I have to admit, I was confused about why I should IF when I already feel and look great with a body fat around 8-9%. I do miss a meal occasionally when I don’t feel so hungry, which doesn’t bother me, but missing two meals in a row makes me feel weak and tired, which is no fun 🙁 IFing did help me get under 10% body fat though, which can be a bit difficult without it, so I do think it’s a useful tool for weight loss.

  52. Just did a 24hr fast the other day. Did a Mark Ripptoe workout with Olympic lifts and I’ve never felt better. That day was probably the most energy I’ve had in a long time. The only bummer was when I actually ate it made me super tired!?!?!

  53. I remember the first time I tried IF without switching over to a low carb diet.
    I fasted for 20 hours starting from 9:00 P.M. to 5 P.M. the next day and my first meal was one hamburger (Yes, it had a bun). About half an hour later I felt extremely tired and within moments of lying down in my bed, I fell asleep for 2 hours. Anyone had any experiences like that before when fasting and having a meal with a substantial amount of carbs after?

  54. One of the great benefits of being primal is that it has helped me learn to tune in to the natural rhythms of my body. When i was all carbed up, I thought of food constantly and ate way too much and too often. Now, I find that things that used to send me straight to the pantry keep me from eating. If I’m really stressed out, I don’t want to eat at all (I suppose Grok needed an empty stomach to run from tigers?) Before, I would overeat during times of stress. I also naturally fast now when I’m sick. Sometimes, I just don’t feel like eating, so I don’t. Or I don’t have time to prepare and enjoy a meal. And then there’s the “bad day hunting”. This is amazing to me since I rode the carb coaster for years and was one of those people who would get really cranky when hungry. After three months of primal, I am seeing a natural tendency to IF more. I suggest people not push it but just let it happen. For the newbie, get over the CW nonsense that you have to eat every 2 or 3 hours. Once that mental leap is made, IF will not be far behind.

  55. Did my first IF last night, having been Primal for about 7 weeks. Did it accidentally as was feeling a bit nauseous, so just didn’t eat supper.

    Pre-primal I wouldn’t have been able to sleep if I hadn’t eaten – I guess my blood sugar would have been all over the place. Plus I would have got really cold and just felt totally deprived.

    Slept wonderfully last night though and no feelings of cold. Noticed that I only got hungry when I remembered I hadn’t eaten – suggesting that perhaps much of my hunger is in my mind! Although I’ve only been Primal for a short while, I’m finding that my hunger seems to be out of habit, boredom or frustration. I’m gaining such a wonderful awareness of what I’m eating and most importantly why.

    The idea that perhaps I now control the food and not the other way around, is quite profound for a female who’s been failing on diets most of her adult life. I’m going to do IF again, but only when it feels right. I’m learning to be nice to my body. And it feels good!

    These comments are so inspiring for a newbie like me, by the way. I’m feeling so supported. Much thanks!

  56. I’m not sure if someone already posted this as I am not able to read the plethera of comments. It should be noted though that IFing does not necessarily decrease your calorie intake. Mark you made a point to say “If you’re training six days a week, don’t IF. Unless you’re genetically blessed, you’ll need lots of fuel to prevent overtraining.” I eat mega-meals post workout to avoid just this thing but still IF consistently.

    When someone begins IF without tracking food intake, then it would be likely the calories would lower dramatically. If you’re paying attention you can stay even with normal, and if you aren’t paying attention it’s easy to even overeat since you could be super hungry and mentally justifying a big feast. Just my 2 cents.

  57. Mark ~ I think this is the best post you’ve done on IF. All good info, especially this part:

    “I recommend that anyone new to IF that wants to incorporate IF should be fully Primal for at least three weeks before trying it. That means getting rid of all excess sugar, grains, legumes, and vegetable oils ….”

    This is key for people new to IF to know. I’m primal all the time, so I can IF whenever I choose to (i.e. I never eat grains, legumes, or vegetable oils). One thing I know for sure is that IF is harder when I’ve been making too many exceptions with sugar, as I do sometimes via espresso and chocolate – the more I have of those things, the hungrier I am and the more I want them, so I’ve learned to keep them to a minimum, because they usually cause more trouble than they’re worth.

    Here’s a great post I found on the myth of discipline. I keep it in mind when I think I want things I know are going to end up hurting me:


    Thanks for a great post!

    Susan Alexander

  58. Mark ~ Another couple of thoughts to add to my last comment:

    1) I’ve found that a great time to IF is during long periods of travel – waiting around for planes/sitting on long flights – I’ve found those are the perfect time to let my body use it’s own fuel. Also, it’s often hard to find good food when traveling, and carrying a lot around with you is no picnic 🙂 so why not go without?

    2) Getting started with Primal and IF takes an open mind. They’re changes, and people have trouble with change sometimes. I think it boils down to this: In order to make a change, we have to believe we can do the change. It all starts in the mind:


    Thanks, Mark.


  59. I was actually afraid to try IF. I guess it was the memory of starving when I was following CW and having to eat every 2-3 hours. I also had hypoglycemia at the time. Dreadful memories. However, after following the PB since July, 2010, I found that I was really not hungry all the time. I was forcing myself to eat all three meals, but was afraid to skip a meal in case I got hungry. (Silly reasoning…It’s amazing how long a habit and old fears can stick!) But, after last week’s post about IFing, I decided to skip breakfast the next day, and I was fine! The “over-stuffed” feeling I was experiencing vanished. I find I can go from dinner to lunch the next day without any real hunger pains. So, for me, IF is a success. But, of course, I listen to my body…eat when hungry, stop when full. (Duh!!! Did I actually need convincing of that? Apparently so…)

  60. The thing for me, aside from only being about 7 weeks into Primal eating, is that I am already dieting (i.e. cutting out 500 to 1000 calories per day on average). Primal has made it much easier to do this, and I have seen results. But when you are always operating on a deficit, it feels that much harder to skip a meal or two.

    The other challenge is work. I work in an office where I need to be sharp all day long. When I start getting hungry I begin getting distracted, to the point where I am afraid I will make mistakes or just be obnoxious to work with.

    It would have to be a weekend day for me.

  61. Great work on the post regarding IF. Every time I do it I usually feel refreshed and energized.

    Does anyone know if there is a certain food that is best after IF? protein? fat?

  62. OH, this is exactly what I’ve been looking for! I only delved into fasting a little bit, and it was about 6 months after giving birth. I couldn’t shift the weight. Actually I think I was under a lot of other stress at the time, and it did make me dizzy and weak, but it also did kick-start fat loss. I only tried IF for about 3 weeks though, but it seemed to be just the turning point and when I went back to ‘normal’ primal I kept losing fat.

    So I started writing about fasting, but then it kind of hit me that it probably wasn’t a good idea for everyone … I couldn’t put my finger on why, and you’ve really nailed it! It makes sense intrinsically to focus on the foundations first.

    Thanks Mark!

  63. I’ve been eating strictly primal for about 6 months now. The health benefits became clear quickly but have really taken a leap from the moment i introduced IF. before i was the 6 meals a day kind of guy – and i should note that i have been following this meal plan for 3 years as a way of recovering from an eating disorder. ‘Leaning out by firing up your metabolism’ is used as a therapy for anorectic or bulemic people; In this country that is.
    The 6 meals a day routine controlled my life and i was constantly counting calories and now and then i would loose control and have a (sugar)binge, but overall during these years i’ve developed a certain dicipline that helped me get over that eating disorder. However one might ask himself if eating 6 times a day and freaking out whenever a meal would be skipped isn’t a disorder on its own? Anyway, as i discovered the primal blueprint i have been able to free myself from any regulation and restriction. It felt great that for the first time i could truly take a distance from my former food obsession. No more calory counting, no more cutting out fat, no more eating when not hungry and finally feeling truly hungry again – what a wonderful feeling 🙂 The usual paleo benefits where noticable very quickly: high energy levels, leaning out, feeling great. i concidered myself truly paleo happy. I felt completely freed and found myself on a constant high.
    However 3 months ago i started experimenting with IF (while maintaining a strictly primal diet) I very quickly adapted to a daily 20 h fast and what happened then went beyond my beliefs. My mood switched from happy to euforic, training fasted increased my strenght significantly, all skin problems disappeared ( i have winter eczema since childhood), herpes: gone!, better theeth and mouth health, i haven’t been sick since (and these German wintermonths have been very hard) , i am getting the leanest i have ever been (estimating a bf of 8%) while my muscle mass is growing, i am more focussed, awake, creative and feeling younger than ever. What i find extremely pleasant is the fact that every night i can feast by eating delicious primal foods and by eating BIG without any counting or fear or guilt. I have fully rediscovered the joy of eating and i feel connected to my body again. Primal eating and living + IF (which i actually consider a logic part of primal living) is working miracles for me and – i think – shows a magnificent physiological and psychological potential for a lot of people, especially when recovering from an eating disorder.

    1. Congrats Boris! Sounds like you’re doing well and this is inspiring for those suffering with EDs.

  64. I’ve been fasting once a year, almost every year (except when I was pregnant or early nursing) since I was 12 years old. It’s called Yom Kippur and Jews have been doing it for thousands of years. Ditto for Muslims and Ramadan. An occasional fast won’t kill you, will clear your mind AND make you realize exactly how fixated our culture is on food. Try it!

  65. I love that line about avoiding things that crush your soul. I love that this blog presents incredibly logical and well-researched, relevant information with a dose of just good ol’ life wisdom. And as far as the dumbasses who blab randomly, I can almost hear the testosterone-deprived high pitch there.

  66. Great, important, follow-up post to the recent one on fasting. IF sure can be used in a harmful, unhealthy way, which is why I almost never recommend it to clients – unless I really know where they’re at emotionally around their health and eating.

    “If you’re stressed, don’t IF.”
    “If life is good, try fasting.”

    Good stuff. Thanks Mark.

  67. Hi Mark –

    I’m glad you posted a follow-up to the original thread. Since finding your site a few months ago, I’ve learned a great deal and your site is one of my go-to places.

    Having said that, I think this follow up post is an example of my general impression of some of your info here. I’m someone who is struggling with obesity and often feel your advice is geared more towards the athelites and persons who are otherwise fit and “healty”. I would love to see more information for those of us who are at the beginning stages — both within a general article as well as articles specific to our group.

    Having said all this, all in all, I’ve learned a great deal and your site continutes to be one of a handful that I read daily.

  68. I enjoy my fasts. I’m slimming down and feeling good even when my 2 meals are really high caloric. I think a culmination of not eating enough the last two days really really made me lethargic to the max. I mean woah. Totally accidental, though, as I was up for almost 36 hours straight and had poor overall nutrition those two days. I bit me in the ass. Hard. I don’t respond well to an extreme lack of calories, at all. Thank God I had eggs, chicken and bacon and lots of veggies on hand. I can deal with small stomach grumblings but this totally wiped me out.
    Keep up the good info!

  69. Great points about letting yourself be flexible about this. One doesn’t need to take the approach that it’s a “strict diet” or follow lots of rules.

    The more I work with IF, the more I’m finding that being flexible helps me get more from it. I sort of follow my body instead of imposing IF as a discipline. Most of the time on a fasting day I feel good, humming along, feels like my body’s loving it.

    But sometimes it just doesn’t feel right, my body needs to eat and I pay attention to that.

    I also read that some people eat a small primal snack or meal of up to about 500 calories — a few eggs, some salami and nuts. That helps sometimes and doesn’t seem to affect the other benefits of IF.

    Came to my attention a while ago that doing mental/desk work with intensity can also increase cortisol. I find that when I have deadlines or work lots of hours at the computer I need to take it easier on the IF or seems to add stress.

    I’m paying attention to IF and appreciate the posts on this site. It seems to be the only thing so far that’s helped me with (needed) weight loss in midlife.

  70. Hi, Mark. Lovely post. Though many people and even some researchers claim that fasting cleanses your system and is good for your health, I don’t recommend it. The reason is that body requires fuel to sustain and shocking the body by denying it the essential nutrients is certainly not desirable.

    1. Albert, “shocking” the body is not necessarily a bad thing. Intense exercise definitely “shocks” the body by inducing lots of oxidative stress, destroying homeostasis and increasing heart rate to up to 90 percent in some cases. Yet if done right, it has a net beneficial hormetic effect on the body. Another example of a hormetic effect are the fruit and vegetable compounds that actually damage certain tissues but the body mounts an effective response and comes out even healthier and more resistant to stress than it was before. As for the denying nutrients, fasting can increase uptake so that when you DO actually get your next meal, more nutrients can be effectively assimilated.

  71. I don’t understand why people get so pinickity about IF’ing. Even in this thread alone, there seems to be some slight hysteria about it. It’s really simple. Eat when you’re hungry, don’t eat when you’re not. After a while, you will naturally intuit when you want to eat or not. Your level of activity will act as a trigger for this. I just cannot see the point in setting yourself yet another rigid doctrine-i.e- i will fast for 16hrs, then eat all my food in 6hrs!UNLESS this just happens to be a natural occurence and that you feel comfortable with it. Otherwise it’s just another bulls**t restriction a person places on themselves for no reason whatsoever. We are not ‘Grok’, and therefore i see no reason why we should be replicating this system on ourselves when infact this was a ‘system’ forced on ‘Grok’, and most likely added to his stress levels. That said, fasting is beneficial to the body at times, but only when you intuit the need for it, rather than forcing yourself. I feel that we all need to start intuiting more, rather than adhering to strict dogma, for example, food grouping comes to mind. If i want a banana without protein that is what i’ll do. ‘Grok’ would have done the same, as he rarely would have eaten a balanced meal of protein/carb/fat. If there was a thousand calories of fruit there, he’s have eaten it.

  72. I have a very popular book on bodyweight exercising that states flat out that you should not fast because it makes the body think its starving and, as a result, reduces your metabolic rate (which is not something you want to do). I’m not sure one’s body would adjust that quickly if you fasted once a week or every two weeks for 24 hours. It seems that the health benefits of fasting are just too significant to ignore. I think I’ll try a full 24 hours. I think if I had breakfast, it would just make me want to eat more later in the day.

  73. Hey I was reading the comments on eating disorders and I’ve been three months clean from bulimia and minor anorexia. In my darkest days, starving was quite the hobby. Sometimes IF brings upon the same feelings however I find it easier to be able to not think about food until night time when I can relax and eat calmly. It is a chance to enjoy my food. I usually eat every 18-22, sometimes 24 hours. I find this easy and accommodating. Just putting my two cents into this blog. Great post Mark!

  74. Really, really sensible article Mark. Reading some of the comments in the first fasting article felt like being sucked into the twilight zone. Massively appreciate the balanced, well-thought-out and sensible point of view. That’s what’s gonna get Primal/Paleo to the masses IMO.

  75. Thanks for breaking it down for us. I think listening to your body is essential when you’re looking at IM.

    I’ve been doing 16/8 and 18/6 every day for several months now, and have recently added in a couple of 24-hour fasts per week. The health benefits are truly amazing, but you’re right. It’s not for everyone.

    Thanks for another great article, Mark!