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

Is Intermittent Fasting Healthy?

If only I weren't so skinny!

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

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

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

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

Well, maybe not.

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

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

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

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

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

The results were surprising and impressive.

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

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

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

So, what are the practical applications of this research?

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

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

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

Let me know of your own fasting experiences.

UPDATE: See this post on Women and Intermittent Fasting.

Further Reading:

My Carb Pyramid

Healthy Recipes

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

Subscribe to Mark’s Daily Apple feeds

You want comments? We got comments:

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

  1. Well, see what it does for you. If eating 6 times a day keeps you svelte and sexy then you are doing what’s right for you, Jeff. I can tell you right now that, as for me, if I ate that way, I would be an overweight diabetic with a horrid craving for doughnuts and Lays potato chips.

    mary titus wrote on July 24th, 2010
  2. Brad Pilon just put out a YouTube video on the “6 meals a day” subject. The gist of it is that when the theory was developed, the extra “meals” were only 45 calories each. As he pointed out, just putting cream in your coffee is a “meal.”

    As far as carbs and working out goes, you’re looking at information coming from competing interests. Energy for your workout has to come from somewhere. If you eat 200 calories of carbs before working out, your body will use those carbs as energy, before burning any body fat, since carbs are a preferential source of energy over accessing fat stores. If you exercise fasted, your body has to pull it’s energy out of your fat stores. So a person who wants to burn off some body fat needs a different strategy than a person with low fat reserves.

    When you’re talking about the Brad Pitt’s of the world, I suspect the diet is more about getting carb energy to fuel a long muscle building workout, since there probably isn’t a lot of fat to burn.

    Sharon wrote on July 24th, 2010
  3. I have been eating less recently and eating less frequent. I am enjoying life this a lot more. Fasting has a place in my life. I don’t do it regularly though.

    If I am traveling and good food is not around then I will no longer feel guilty about skipping a meal!

    Primal Toad wrote on August 6th, 2010
  4. Hello all you IF’ers out there in computer land. For those of us (myself included) who want to look like Ryan Reynolds in blade or something close to it. Through my seemingly endless search of the interwebs and my correspondance with Timothy from this blog. I have stumbled upon the holy grail-if you will-of IF and getting ripped. The site is called Martin Berkhan is a genius and gives you all the info you need to succeed on your own. Check it out, you will not be dissapointed.

    Jeremy wrote on August 9th, 2010
  5. Mark!
    Thanks for the wonderful website. I’m very new to IF and would like some advice. I’d like to combine IF with the condensed eating window. Here’s what I was planing to implement, please critic and refine!

    Fast from 7:00 pm until 6:30 pm
    Eating window 6:30 to 7:00 pm

    Repeat cycle.

    Does this sound healthy, assuming I’m getting the correct nutrients during my eating window?

    Thanks for any advice you can provide.

    Elizabeth wrote on August 11th, 2010
  6. Mark,

    Just wanted to throw my two cents in here… I did a fast only drinking water 85% of the time and coffee and DIET soda for the other 15% for 72 full hours. Let me just say that I felt great. No hunger pains, no brain fog and plenty of energy. I did not go to the gym those three days, but just did some walking. I was following a low carb/paleo eating plan at the time. If you tried doing this after being on the standard high carbohydrate diet, you would probably get massive headaches and feel very weak. I was simply amazed at the results. I felt much better and plan to start doing IF more often, not necessarily for 72 hours each time, but at least 24 hours. The key to making it work was drink lots of water, it keeps you full and satisfied.

    Mark thank you for all that you do. This website is so helpful and has changed my life.

    -Nick S. Chicago, IL

    Nick S. wrote on August 16th, 2010
  7. Hey Mark,

    Great stuff you got here. I adhered to mostly primal lifestyle now and am having results. When I have better results, I will post it on your site.

    But, I am interested in knowing more about IF for people with diabetes. Can you shed some light in this area ?


    Harvey wrote on September 10th, 2010
  8. I have pre-diabetes and I am able to improve my glucose levels on IF. I do IF on a daily basis and I build my health on intermittent fasting. The more paleo I can keep my daily menu the better my glucose levels. But what really was a boon to my health was the discovery of magnesium deficiency. This came about after I had read that low magnesium levels among other nutrients can manifest itself through headaches. I began taking magnesium for my headaches instead of OTC pain relievers which worked just as efficiently as the meds.So I began to ponder a conection between headaches and insulin resistance. So I researched magnesium and found out that one of magnesium’s job was to manage blood glucose and insulin. I began taking magnesium on a regular basis and my glucose levels have been well within the normal range.

    I just read an interesting article on enzymes and it states that during fasting our body goes through an increase of enzymes making them available for healing and repair. The article actually was pointing out the importance of consuming raw foods and how their consumption also contributes to a higher level of enzymes circulating in the blood.So I am considering increasing raw foods in my diet…something that I have never considered before. Hope this helps


    mary titus wrote on September 10th, 2010
  9. Thanks for sharing this.

    I know when I first heard of fasting I was extremely sceptical, especially after I had been eating 6 meals a day for 5 years!

    After taking a leap of faith with the worry that all my muscle would vanish I tried it, and to my amazement it was amazing. I’ve been doing it for about a year now and have found it incredibly easy.



    Tom Taylor wrote on October 18th, 2010
    • Tom
      What exactly have you been doing for the past year? And how did your body adjust to the switch? Have your workouts changed? I’m definitely a grazer, but would love to try IF. Anything you could share would be helpful.


      Kelly wrote on November 26th, 2010
  10. One of the strongest arguments against intermittent fasting is that it will slow down your metabolism. In one study, intermittent fasting was associated with more than a 40% reduction in heart disease risk. Fasting was also linked to a lower incidence of diabetes. The study was published in October in the American Journal of Cardiology. We just have to burn those hidden fat in the phoenix self storage.

    tom wrote on November 4th, 2010
  11. I practicing intermittent fasting and believe it works great for maintaining my weight and fits well around my lifestyle which involves strength training and some running. I do however feel some of the other commments here detract from the potential validity of IF when they start mentioning ‘nerve energy’ ‘toxins’ and other voodoo, toxins are a myth splashed around to sell bull**** diets, supplements, books etc and I don’t even know what nerve energy could possibly mean. I also think some here are getting abit too excited about animals, which are usually alot less relevant than you may think. Just trying to add some perspective, yours sincerely, a fan of IF

    Icarus wrote on November 8th, 2010
  12. Animal studies*****

    Icarus wrote on November 8th, 2010
  13. So here is what I have been doing. I have tried every diet out there and had some success with all. I finally bought Brad Pilon’s book Eat Stop Eat and applied it. I fast two 24 hour days a week, I drink black coffee and lots of water during. Then I break my fast and eat like I normally would. No huge meals or anything like that. I excercise 3-5 days a week doing P90X mostly.
    When I wake up ill eat in an hour or so. And then I just eat a bowl of oatmeal with brown sugar and a little cream, or maybe ONE pancake, or a couple of eggs. Thats it, then for a snack I MIGHT have a handful of nuts I might not. Or a protein bar. Or not! Then for lunch I do a half sandwich and soup, or just a small meal of fish and broccoli, chicken and noodles and cream sauce whatever but the point is, the portions are small!! If I went to Pizza hut for lunch I would gorge myself with the salad bar eating only SALAD, Peppers and thats it, and then I eat two slices of pizza and no more. So I enjoy what I eat just not a bunch of it!! at dinner I eat whatever, spaghetti, pizza, steak and potatoes a normal dinner and one generous plate and thats it. At evening ill have a few chips, or some gummy bears, or a beer or two and thats it. The first two weeks alone of this diet, I lost 10 pounds. I am down to 179 which is about as light as I have ever been and no diet has given me results like this one does. I keep my calories to about 1200-1700 a day preferrable but if I go over like I did yesterday where I just pigged out on candy bars after halloween, I don’t care! I am fasting today and ill eat better the rest of the week with another fast and excercise and ill still be in a caloric deficit! And my muscles are GROWING!!:) Remember you MUST BURN MORE THEN YOU TAKE IN!! Forget protein!! forget carbs, ect. eat more veggies and fruit always, and burn more then you take in, you will lose weight and if you do strength training 3 days a week, you will build muscle if you lift heavy for 8-10 reps a set. if you lift light you will get lean and not lose muscle! I hope someone else has as much success as I am having after reading this. My 6-pack is almost here for the first time in my life!!!!:)

    Jeff wrote on November 8th, 2010
    • What kind of how old are you?
      Are you M or F?
      What kind of exercise and how much are you doing?

      And really Gummy bears? I would rather have a steak but to each their own.

      I put in my routine on a post today if you want to know what I do.

      Thanks, and congrats on that 6 pack. I want to see that on me within a year.

      Troy wrote on March 25th, 2011
    • Sorry I missed who wrote at the bottom, so you’re Male.

      Troy wrote on March 25th, 2011
    • Dude uless your 5ft tall, at tf ease.

      You don’t really explain how you fast and what your doing besides eating anything you want kinda but your were only 185 lbs. that aint shit either be more specific in you body and orig weight or get real. I am 269 lbs and have been as high as 298 lbs and been as low as 210 lbs and am 6ft tall. so I need to figure out how to keep it off, i have been doing the BFS every day and fasting everyday but one night a week but really not sure what I shoud be doing for the IF but you loose 10 lbs at your weight , i have lost twice that in a week like nothing. I think you need to just work out harder and finally did it, sorry but congrats to your new found thing.

      Tpattison wrote on May 17th, 2011
  14. Ive been doing a fasting diet where i fast for 16hrs (usually from after dinner) and at the end of the fast you have a half protein shake or 2 egg whites to stimulate production of bcaa and hit the gym a hour after that or go for run on non weight days, and then have a big hit of protein and carbs (usually 3 whole eggs and 3 egg whites scramble on toast) and banana or something, then later with dinner i make sure i get 2 cups veges to get the nutrients ive missed out on (you can add a multi vitamin) and then once a fortnite mix it up with a 24hr fast. THIS REALLY WORKS I have dropped 5% body fat and gained 2kg muscle so far!

    sean wrote on November 15th, 2010
    • That sounds great, but where are you starting from?

      where was your body fat to start?

      How can you tell how much muscle you gain?

      Is 2kg about 3.6 lbs?

      did you plateau before?

      How long did it take to get those results?

      For those of us that are not that smart, is fort night every 4th night?

      Troy wrote on March 25th, 2011
  15. I’ve been researching IF and have found this site VERY helpful… however, there are many different approaches, and I’d like to get some suggestions on an easy way to ease into IF. Does anyone have any books they’d recommend to me? Thank you all for your wonderful posts!

    Kelly wrote on November 26th, 2010
  16. This gets really interesting when you combine the idea of IF and new research that shows certain bacteria in the gut are to blame for obesity and insulin dependency. Maybe a one-day fast works by starving and killing off the “obesity” bacteria.
    I suppose it might kill good bacteria too, so it might be a good idea to follow up with normal yoghurt (acidophilous) on the next normal eating day.

    Mai wrote on November 30th, 2010
  17. I need to lose at least 50lbs and I am planning on working into IF fasting. What seems the best pattern for myself would be to eat a big evening meal and then work myself up to not eating until at least 1 or 2pm the next day. One question I have: I have a pacemaker/defib. implant. My heart is healthy except for the electrical. No blockages or any problems like that. But I still have been perscribed a low doseage beta-blocker twice a day. And because I have to eat something with it in the morning…what would you suggest I eat that wouldn’t upset my fast too much? It doesn’t take much.

    Toni wrote on January 15th, 2011
  18. Personally, I would work my fast around your pacemaker needs at the least. You need your beta blockers in the AM,with food, that is when you should break your fast. However, with your situation, I would also discuss this with your doctor. You probably should keep a close eye on your electrolyte balances. These tend to drop when eating habits change.

    mary titus wrote on January 15th, 2011

Leave a Reply

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

© 2016 Mark's Daily Apple

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