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

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

  1. I just got done watching a tv show about two docs in the jungle in africa to see how they used plants as medicine. What was amazing to me is on the days they didn’t get an alligator, they ate honey combs and veggies. I think back then there was more honey bee’s in the wild than what we think today. And those guys were ripped. So yes I fast 16/8 my self but on some days I am going to try this and eat raw honey comb and veggies a couple times a week and see where it takes me. Think about it even in ancient times they did drink a lot of mead and that takes quiet a bit of honey. Something to think about

    Lane wrote on July 20th, 2011
  2. IF has been an amazing lifestyle change for me. I have an interest in building muscle so I used to be one of those people who was obsessed with getting protein every 2-3 hours.

    With IF, it is so liberating to not have to constantly think of food!

    Duong Nguyen wrote on July 27th, 2011
  3. hi I am a 16 year old high school student. I wonder if IF works for adolescents in the middle of puberty? Or do I have to dine three times a day to assure maximum growth?

    Damdam wrote on July 28th, 2011
  4. Do you believe in the mitochondrial hormesis concept, which, as I understand it, basically suggests that by subjecting your body to great oxidative stress caused by fasting that your body adapts by better tolerating and dealing with exogenous radicals and other toxic compounds?

    LEC wrote on July 28th, 2011
  5. Damdam, Once upon a time fasting was a part of every diet. It remains a part of today’s diet actually which is where the word “breakfast” comes from. The most important meal for breaking your fast is indeed breakfast but when you break that fast is totally up to you. I encourage everyone not to drastically change your eating plans. Instead coast into fasting by eating dinner a little earlier and/or eat breakfast a little later. Do this slowly on a day by day , week-by-week- and month-by-month basis until you can easily eat once or twice a day. If your diet is rich in protein and other nutrients such as B vitamins, magnesium, healthy unadulterated fats, vitamin D, there should be no reason why a healthy adolescent can’t do intermittent fasting. I strongly believe that in order to have a healthy fast you must primarily have a healthy diet. Your last meal of the day should be rich in foods that help stabilze blood glucose such as chicken, seafood, pot roast, flounder, lamb, organ meats.Most vegetables are low in carbohydrates and good choices are turnip greens, kale, collard greens,spinach, turnip roots,asparagus, artichoke hearts, summer squashes. On days when you feel that you need more vegeatbles remember your vegetable juice. Check the contents label for carb content and choose the juice with the lowest carb content. Make sure that you use butter, cream, olive oil, coconut oil liberally and without fear. Some fruits to consider are raspberry, blackberries, strawberries, bell peppers of all colors, tomatoes, avocadoes, cantalope, grapfruit. Honestly, I wish my diet as an adolescent were this healthy.

    Mary Titus wrote on July 29th, 2011
  6. This diet is just too convenient to quit…

    I’m 7% body fat all year round.

    Aaron wrote on July 31st, 2011
  7. Funny… this blog is ABOUT fasting not whether a fruit will kill you or not, which it doesn’t by the way.

    I fast once a week on a Sunday since it is my quiet day and I do my enema at the same time, which gives a total detox experience.

    Been doing this routine for the last 3 years and I am still at 9% body fat.

    Karl Roberts wrote on July 31st, 2011
    • I fast Monday, Tuesday (tuesday– wow, my finest day) eat light on Wednesday, fast Thursday, eat “aveage american diet” on Friday Sat, and Sun. I take 10 grams of powdered Vit C/Mag in a glass of orange juice in lieu of enema. For those that love that “cleaned out GI” feeling, mega dose of Vit C is an incredible alternative. not only cleans you out but so many more incredible benefits– not the least of which is anti-inflammation.

      mory wrote on July 31st, 2011
  8. Funny… This blog is about fasting NOT whether a fruit will kill you or not, which it doesn’t by the way.

    I fast once a week on Sunday because it is my quiet day and do the enema at the same time, for a total detox experience.

    I simply drink Peppermint, Milk Thistle and Yerba Mate teas all day.

    I’m still at 9% body fat for the last 3 years without breaking a sweat.

    Karl Roberts wrote on July 31st, 2011
  9. I started doing this about 5 months ago. My weight at the time was about 250 pounds. Depressed and unhappy I made this simple move to ADF and it changed my life. In that time have dropped to 198lbs, I look younger and feel like a million bucks. I follow a strict ADF 24hr eat 24hr fast.
    Mon Eat Breakfast, Lunch and dinner
    Tues Miss breakfast Miss Lunch Eat dinner
    Wed Eat Breakfast, Lunch and dinner.
    The best part is that I start end my fast at night so I always get to eat dinner. On the eat days I eat until I feel 100% full and never feel like I am eating on a diet. Note food intake is nothing processed and a meat and veggie diet, on fast days only water. I never fast more than 24hrs. I have done tons of things but this is the one sure fire method for losing weight. My brother is pushing 400lbs and he just started this program too. I cant wait to see his results. Best of luck to anyone trying this and making it part of their life.

    Scott wrote on August 22nd, 2011
  10. Congratulations Scott, That is wonderful. May I ask what kind of foods do you eat when you break your fasts?

    Mary Titus wrote on August 23rd, 2011
    • Anything but pre-pkg food no soda no fried food. However I do go out to eat and cheat once in a while. I enjoy eating as we all should and when I eat I make something that will provide energy for my next fast period. I love sushi and eat out twice a week for that! Good luck.

      scott wrote on August 23rd, 2011
  11. I’d like an opinion…. I’ve been fasting about 90 hours a week– Monday, Tuesday, eat Wednesday, fast Thursday- then eat through Sunday evening. Been doing that for 6 months; I’m very comfortable in this schedule– look forward to my fast days and the energy it brings. But recently, I’ve been reading that Glucagon reaches it’s peak at about 60 hours, and concomitantly, the peak of growth hormone. so…, 90 hours is over kill– right? I’m thinking of just going for a straight 60 hours and doing it all in one fell swoop– Sunday night TO Wednesday evening, eating normal the rest of the week. Does anyone have experience with this, or know which of these plans would bring better health?

    mory wrote on August 23rd, 2011
  12. I’ve been practicing IF for 6 weeks. I do 16 hour fast on a few days a week (if I don’t feel like breakfast) and do 20-24 hour fasts twice a week. I also eat primal blueprint. I do 40mins HIIT daily plus weight training alternate days. I have a cheat day once a week where I usually stick to lower carb.
    I’ve lost 23lbs in 6 weeks.

    sannie wrote on September 2nd, 2011
  13. I started out with a combination of two types of intermittent fasting: 1. Eating all of my meals for the day within a 8-9 hour period. 2.A total fast for a 24 hr period once a week. I dropped fat fast and find it very easy to take weight off when I put on a couple pounds after a less scheduled weekend of eating. Now I primarily do one 24 hr fast a week and skip breakfast with the occasional 250 cal post workout shake to maintain leaness below 10% bodyfat and still eat fun food. I agree that it is such a relief not worry about eating every 3 hrs and I’m much less of a slave to food.

    Zane wrote on September 6th, 2011
  14. IS there a difference of how the weekly fasting effects you if you younger like 15, if you skinny or fat?

    Ryan wrote on September 15th, 2011
  15. And is your a boy or girl

    Ryan wrote on September 15th, 2011
  16. ME and my friend want to do an experiment of our own on the subjected, does anyone know any experts we could talk to?

    Ryan wrote on September 15th, 2011
    • Hi Ryan,

      You can judge for yourself whether I’m an expert, but feel free to email me via my website if you want to tall experimental with me.


      George SuperBootCamps wrote on September 16th, 2011
  17. i need someone who went to school for the subject so i can prove to my teacher there an expert, so if you did id love talk to you

    Ryan wrote on September 16th, 2011
  18. Ryan, here is a well educated cardiologist who is very familiar with the subject. His name is Dr. William Davis and he writes the Heart Scan Blog. Here is an article he wrote on fasting You could email him.

    Mary Titus wrote on September 16th, 2011
  19. Hi everytime i IF the inside of my lips and gums peel and can pick bits of skin off. Anyone else have this or anyone know how to stop it happening?


    mitchy wrote on September 24th, 2011
  20. Mark,
    What you explained about your 79 year old friend. He actually is fasting longer than 24 hours.

    I found that fasting that way sometimes made it hard thinking I was not going to eat ALL day.

    One thing that I came across years ago that I like is a true 24 hour fast.
    The difference with it is you could start at any time that worked for you. So if normally my 1st meal was at 6 am. I would eat every 2-3 hrs (6,9,noon,2). Then I would stop from 2pm -2pm the following day. The following day I would eat 2pm, 5, and 8. So I fast for 24 hours but actually get to eat both days.

    Andrew wrote on October 1st, 2011
  21. I am a bit confused, because I thought the IF was an Intermittent Fast. It seems that if people are fasting every day, or every other day, it’s not really intermittent? Practically speaking, would you then not be just getting your body accustomed to a lower caloric and nutrient intake, rather than mimicking the feast and famine concept of our ancestors…sometimes food is readily available and even abundant, and other time food is scarce?

    I know that if you find your body composition goals plateauing, a good way to notch up your leptin response is to have a feasting day followed by a fasting day…intermittently. Not all the time! By operating at a calorie deficit for as little as 6 to 8 days, I have read that the levels of leptin can drop up to 50%. Then it would make sense that your body is in famine mode, releasing cortisol under the stress caused and resulting in more fat storage. So if you feast for a day, say one day a week or two and then fast the next day, it sends a different message to your body- that food IS readily available and your leptin levels increase. After say, 12 hours of eating more, then you fast for the next 24, which puts you into a caloric deficite right when the leptin levels have increased, thus signalling to your body to burn available fat stores…because you have just revved up your metabolism by eating. Then the rest of the time, you eat your normal 1800-2000 calories a day ( or whatever is normal for you based on activity levels) and of course, keeping up with a Primal way of eating.

    I can see how the body will continue to lose weight by fasting…but should we not also be concerned with taking in appropriate micronutrients on most days? I look at eating Primal as a way to really boost my micronutrient intake naturally, without excessive supplementation. If the discussion is IF, then doing it every day does not seem….intermittent!

    I am curious to see the responses I get to this!

    Primaldawn wrote on October 14th, 2011

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