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. There is well over 100 years of scientific data behind fasting. Check out the National Library of Medicine for tons of great info. Many Universities are studying fasting right now and have been for many years. The benefits are well know to ‘mainstream science’ however not many people are willing to fast even if it could save there life.
    Jordan O’Hara

    Jordan O'Hara wrote on April 8th, 2009
  2. I hope it is okay to post this here. It is a blog entry on fasting, ketosis and metabolism. Quite interesting and it is one of my favorite posts. Thanks Dr. Michael Eades.

    Mary Titus wrote on April 8th, 2009
  3. Mary Titus wrote on April 8th, 2009
  4. After i broke my fast is it ok that i ate solid food or ate a lot of rice and fried chicken,meat etc.

    toats wrote on April 9th, 2009
  5. Toats, there are 2 concepts on this. How long was your fast? I know that some who have lengthy fasts of 2 or more days experience tummy distress upon breaking a fast with a heavy meal. I rarely fast beyond 24 hours and my meals are according to what I want to eat. I may REALLY want a large meal. If this is the case, I eat a large meal. I do low carb so my meals will have some form of meat/fish/chicken. I also try to eat 1/2 to 1 whole avocado, veggies ( especiallly collard greens, turnips, celery root ). If I have a small appetite, I eat according to that when I break my fast. This may be as small as some homemade chicken salad with a 1/4 of an apple.

    Mary Titus wrote on April 9th, 2009
  6. you mean theres no problem regarding eating a lot of solid food after 24hr IF as long as u can bear it,ive heard people that skipping meal can cause ulcer can u please enlightened me about this.

    toats wrote on April 11th, 2009
  7. sorry i forgot, can i take my vit.calcium (500mg)after i break my fast,i prefer my window at 7 to 12pm started today.

    toats wrote on April 11th, 2009
  8. I eat exactly what my body wants at the end of my fasting. Yesterday, for example, I had a baked chicken thigh, 1/2 sliced avocado, and a mix of collard greens and black soy beans ( cooked Southern style ). I add plenty of butter and other fats to my diet. I topped that off with a a serving of sugarfree chocolate pudding. IMHO, the ulcer fear is mythical since it is bacteria that causes an ulcer…not the digestive process. Plus, I try to fast with the mind of a cave woman and she has no clue what an ulcer is. She eats when she can and all that she can cause she has no idea when her next meal might be. All I require of myself is making sure that my food is low carb and healthy.

    Mary Titus wrote on April 11th, 2009
  9. Oh and about your calcium, I think that it would be just fine to take your calcium or any other supplement right after you break your fast. That is when I take mine.

    Mary Titus wrote on April 11th, 2009
  10. I take digestive enzymes when I break the fast. With those I have no trouble with solid foods.

    Jordan O’Hara

    Jordan O'Hara wrote on April 11th, 2009
  11. how come that one of our friend she told me it might harm you due to our small intestine doesnt have anything to grind,about IF or(skipping 2 meal)

    toats wrote on April 12th, 2009
  12. Toats, I don’t know why your friend would say that. It makes no sense to me. My gut feels great. In the beginning, there were no grocery stores, no candy bars, no McDonalds, no Pizza Huts. In other words, food was very difficult to come by.There was no way that life could have existed without an extended fasting period. That being said, we all fast. I ate dinner tonight at 7:00 PM. My next meal will not be sooner than 12 hours away. That is, if I eat at 7:00 AM. I don’t even plan on getting up until 9:00 and I may not eat breakfast until 11:00. That would be a minnimum of 16 hours going by without food. My small intestine will be just fine. It takes 3 days for some foods to even digest completely, so I doubt that a reasonable fast would harm any part of the digestive tract. My husband will have surgery on his large intestine and fasting is going to be necessary for a few days. This is to allow the intestine to rest. I had a colonoscopy which required me to basically fast fro several hours. My mom had to fast to heal her pancreas from pancreatitis. If fasting can be used to heal the digestive tract of those who are ill. I am sure it won’t hurt someone who is healthy. I think that the digestive tract does indeed needs rest. After doing this for 2 years, my gut feels much better.

    Mary Titus wrote on April 12th, 2009

    This is a site that has many references to IF. It includes many that I have investigated while considering IF as a part of my lifestyle. I believe that I cam upon Mark’s Daily Apple through one or more of these sites. Hope they are helpful.

    Mary Titus wrote on April 12th, 2009
  14. I’ve been doing the fasting now for 3 weeks. Today is the third day. So far I’ve been doing it where I eat dinner the night before and then nothing until dinner today, about 24 hours. I don’t normally make it with NOTHING all day. Last time I ate two cheese sticks and a few pieces of fruit. I would rather not do that, but frankly the low blood sugar, shaking, and feelings of weakness drive me crazy. Is this not normal? I also notice that I have a pretty short fuse on these days. I am über cranky. Does anyone else feel this way?

    Jac wrote on April 29th, 2009
  15. Jac – most people starting fasting have the same issues you mention to different degrees. However, these side effects do normally completely subside over time. Your body needs to complete a physiological adjustment to the new healthy lifestyle condition. It’s just like quitting a bad habit like smoking. Just takes time to comfortably adjust to the new healthy ways.

    Jordan O'Hara wrote on April 29th, 2009
  16. In my honest opinion, Jac, you are not eating enough. When I break my fasts, I do it with a butt load of food to make sure that I make through to the next time that I eat. For example, a T bone steak with 3 bean salad and sliced avocado. When I began to IF, I would add a glass of V8 juice. PLUS a nice low carbohydrate dessert such as strawberries with full fat sour cream with a scoop of whey protein . Now, that’s what I call eatin’. I eat like a cave man. My blood glucose remains stable. I am also even tempered. Supplements such as MCT oil,vitamin D3,Krill and B vitamins are also a part of my diet.

    And, like Jordan O. says you do indeed have to allow your body to make necessary adaptations. But, make sure that you are eating enough food. Remember the best part of a fast is the meal that breaks it.

    Mary Titus wrote on April 29th, 2009
  17. Also, think of the financial savings! That’s why I’m doing IF. We’re basically not eating for six months a year with a one day on/on day off IF. That means no money spent on food for six months!! Imagine the savings $$$!!!

    Also, think of the time saved. Now I don’t have to stop working or whatever in the middle of the day to eat lunch – I just keep on doing whatever I’m doing. I can work later, too, because I don’t have to come in for supper on my non-eating days. IF has major time and financial savings.

    elliott wrote on May 1st, 2009
  18. Hey Guys

    I did the Lemon Detox with the Madal Bal for 7days. Lost about 6 KG. I could not believe how great I felt. I eat between Midday and 8pm usually and I am thinking of bringing that in between 1pm and 7pm now. The only things I touch outside this Period is Water, Green Tea, Bee Pollen Capsules (High vitamins and minerals) and Fresh Lemon Juice.

    I have never Felt better. I am going to start adding some intencse short workouts in as well between meals in the eating period. GO IF!

    I think it is something that needs to happen more in daily living in the western world.

    Stephen wrote on May 6th, 2009
  19. I’m very new to this but I have a question about IF. What about headaches? If I just skip breakfast I will get a headache by 1:00 if I don’t eat lunch. It’s hard to work with a headache.

    Anna wrote on May 21st, 2009
  20. If you are new at this, why would you go until 1:00 without eating? That is not the wise way to fast. At least it is not the way I began doing this. If you normally eat breakfast at , say, 8:00 AM. Eat at 9:00 AM for a few days, then eat at 10:00 for a few days. Continue doing this until you work yourself up to your desired oficial time to break your fast. If you experience headaches and have no insulinemia issues, try taking a magnesium pill. Sometimes headaches are caused by low magnesium. I don’t even use Tylenol or aspirin anymore. I take a magnuesium supplement and my headache vanishes just as if I had taken an analgesic. However, I rarely get headaches anymore.

    I do not believe that you should do intermittent fasting without allowing your body time to become accustomed to the change.

    Mary Titus wrote on May 21st, 2009
  21. I guess I wasn’t very clear with my explanation, sorry. I have not fasted in any way. I meant that I was new to the whole primal way of living. There have been times in my life when for one reason or another I have skipped breakfast, or eaten lightly, and been too busy to grab lunch until late in the day. That is when the headaches start as well as some of the same experiences that Jac expressed he was having.

    Anna wrote on May 21st, 2009
  22. We all fast. It is just that we are not aware of it. If we didn’t fast there would be no need for break-fast.I posted my concept of IF. That is how I began doing it. I eased into IF until I could go successfully to 3:00 in the afternoon. I have been doing this daily for 2 years. I am also a strong believer in reducing or even eliminating all sugars in the diet. You want to keep your insulin stable so toss the sugar. The best way to make it through a fast is to eat a high protein, ketogenic meal the night before. Also take your supplements at dinner time. You are getting headaches because you are waiting until 1:00 PM to eat. Don’t do that…you are not ready. If you were ready you would not get the headaches. Also if you are not accustomed to eating low carb, that is something else you will have to ease into for what I think would be the best results.But if you want to be able to go through the day without the headaches, you first must address the possibility that you may be experiencing low magnesium. Also address glucose issues. If your insulin/glucose are not stable, that can slam you with a headache. Hence make sure that you consume a hearty protein/moderate fat meal.

    Mary Titus wrote on May 21st, 2009
  23. Thanks for the advice Mary. It is tough eliminating carbs from my diet espcially since I am a sugar addict. I am trying to ease in to that though, cutting sugar first then going for the breads and pasta. I will keep all this in mind when/if I try fasting.

    Anna wrote on May 21st, 2009
  24. Yes, it is tough. You must decide what foods you want to be addicted to. Sugar is not healthy. Anything that will rot your teeth as easily as sugar should not be consumed so regularly. Just imagine what it can do to your insides.
    Good luck on your journey.


    Mary Titus wrote on May 21st, 2009
  25. Hi,, I’ve read about i. f. and it sounds really good. I have one concern though. I am 5’4 and my weight is around 110 pounds. I eat well, and although I am vegetarian, I ocasionally smoke so I want to kick off the habit and try some fastings as well. The most I’ve done water fasting in the past is 2 or 3 days. However, I want to do a cleansing, empower my brain, clean my body. My only concern is how much could I do the fasting if I am mainly skinny, and I have a good metabolism? I guess my point is, how to fast in order to detox my body and my mind, without really losing more weight? What do you recommend? Is I.F. for me? Or should I try a juice fasting instead? Thanks.

    Stardust wrote on May 21st, 2009
  26. I do IF on a daily basis. I do it for its ketogenic characteristics. My body runs better on high octane ketones.This meaning, I eat a normal balanced ketogenic diet in concert with IF.I think that fasting in its own right, cleanses the body without any help especially if you have a healthy metabolism. I am not a vegetarian and cannot really give you any advice that I would feel comfortable with BUT, I do think a juice fast would be counter-productive unless it is done with vegetable juice. Sweeter fruit juices have sugars that will swiftly impact your blood glucose. This would cause your insulin levels to rise and glucose levels to drop, which causes stress to your metabolism. Everyone should strive to keep both glucose and insulin levels under control.

    Keep in mind that the purpose of IF is not to eat less food…it is to eat less often to allow the digestive system to complete the digestive process. By allowing the process to complete itself you will be amazed at how your body will cleanse itself. TMI, I know but this is significant. I have a nice BM that follows within 2 hours after eating my fast-breaking meal. Please note, that I did lose weight but it was only 22 pounds in 2 years. That’s not very fast. If I wanted to do this without weightloss. I eat within a 4 hour periods each day. So between 2:00 and 6:00 is when I eat. I eat whenever I want including snacks and 2 meals, which is my standard rule. The difference with that is, once I break my fast with a large caveman meal, my hunger is much milder througout the day.
    So if I ate according to my standard rule, I am sure that I would not lose…at least not as much.

    I would like to add that doing IF consistantly for 2 years, I have concluded that this isn’t something to do on occasion unless you do it for religious reasons. I believe that it should be done with some type of regularity to maintain healthy metabolism. But, that’s just me. Good Luck,

    Mary Titus wrote on May 22nd, 2009
  27. Plenty of research out there about IF and it’s benefits for the glucose metabolism and it’s neuroprotective stress responses. IF is not CR (Calorie resistriction) yet has many of the same health (and more) benefits. That is pretty amazing in itself. Here’s just one study:

    “A consistent hormonal response to a decrease in food intake in rodents, nonhuman primates, and humans (30, 31) is a reduction in insulin levels and an increase in insulin sensitivity. We found that mice subjected to IF exhibited decreases in serum levels of glucose and insulin to levels at or below those in mice fed daily but with a 40% reduction in caloric intake. The ability of IF to alter fasting levels of insulin and glucose was independent of overall caloric intake.”

    “The findings of this study suggest that IF can enhance health and cellular resistance to disease even if the fasting period is followed by a period of overeating such that overall caloric intake is not decreased.”
    both from study: Intermittent fasting dissociates beneficial effects of dietary restriction on glucose metabolism and neuronal resistance to injury from calorie intake

    If you improve the state of your glucose metabolism, you will lose fat. IF (even if just 1-2x a week) + Paleo foods will get you lean and healthy…IFOC (IF on Crappy foods) doesn’t work as well….simple as that.

    You can also read about different approaches and 100s of comments about how people are using IF here: >a href=””>Intermittent Fasting 101

    Mike OD - Lifespotlight wrote on May 22nd, 2009
  28. sorry….messed up the last link above…here it is again:

    Intermittent Fasting 101

    Mike OD - Lifespotlight wrote on May 22nd, 2009
  29. Great info Mike OD,

    This is stuff that I read before doing IF. You put it all in a nutshell.


    Mary Titus wrote on May 22nd, 2009
  30. Hi, I have been eating a ‘caveman’ diet for two years, eating 5 meals/day, eating around 100-120g carbs/day.

    I exercise 4x/week using heavy weight compound exercises.

    On those occasions when I have purposely skipped a meal on rest days, I notice a definite reduction in strength in my weights workout the following day.

    May be i’m doing something wrong but I can’t combine IF and weight training without a measurable negative impact on strength.

    I’d really appreciate any thoughts/comments.

    andrew wrote on June 2nd, 2009
  31. From what I understand growth hormone production is stimulated with a combination of factors; Decreased blood glucose levels, increased blood protein levels,carbohydrate-restricted diet, FASTING, increased protein diet, free fatty acid decrease, PGE ( a good eicosanoid ) Stage IV sleep ( circadian sleep ) and exercise.This can be found on p. 191 in Protein Power by Dr. Michael Eades. There is more info on this but I would logically assume that if I have been consuming a lifestyle that is opposite from what I have listed here, it would indeed take some time for the body to adjust to the new lifestyle.Once the adjustment has been made, you should deveope muscles that will have a better sustainimg power.I think that it is worth taking the time to do it. I am not a weight trainer nor am I an athlete but I feel the best that I have ever felt…ever. I plan on running in a 5K race in November. During this race, I will just be finishing up my fast. I will not eat my first meal for anotther hour. By-the-way, I fast everyday.

    Mary Titus wrote on June 2nd, 2009
  32. I have been doing a complete fast with one 24-hour day per month for nearly 30 of my 36 years as part of my religious experience. I can vouch for how it is amazing to refocus the mind: I used to believe that I derived this benefit from all the practice I got from trying so hard to think about things other than food; so nice to know it is from a physiological effect too!

    Kelton Baker wrote on July 3rd, 2009
  33. I have been doing a one day a week 24 hr fast for the last 4 weeks. It gets easier every week. I find my strength and cardio workouts don’t suffer.
    Also, during the days when I’m not fasting, I eat about 100 calories every hour. This combo works great for me.

    Michael wrote on July 9th, 2009

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