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

Why Fast? Part One – Weight Loss

plate“When a person has nothing to eat, fasting is the smartest thing he could do.” – Herman Hesse, Siddhartha.

I like that quote. It’s making (non-caloric) lemonade out of lemons, and for all the transcendental insights contained in Hesse’s book, this line strikes me as a really cool, no-nonsense way to make the best out of a bad situation. No doubt about that. But how useful is it, really, to today’s readers? Very few of us ever have “nothing to eat.” On the contrary, food is ever at our beck and call, with very little effort required to obtain it. Actually, that’s not completely true. Processed junk and fast food is readily available, while the good stuff – fresh meat and veggies, actual, you know, food - requires prep work, cooking, time, and the doing of dishes. But the main point stands: we rarely go without.

That doesn’t mean the quote is useless. In fact, with a few slight modifications, it becomes extremely effective weight loss advice. Check out my version:

“When a person has had too much to eat, fasting is the smartest thing he could do.” – Mark Sisson, Mark’s Daily Apple.

If that sounds harsh or even unrealistic, consider the story of the Scotsman. Back in 1965, an obese Scotsman of 27 years and 456 pounds came to the Department of Medicine in Dundee, Scotland, with a problem. He needed to lose weight. A (1/8 of a) ton of it. The doctors suggested maybe not eating for a few days could help. It was just an offhand recommendation, but our Scotsman (known only as “AB”) really took to it. He stayed at the hospital for several days, taking only water and vitamin pills while undergoing observation to ensure nothing went wrong. When his time was up, he continued the fast back at home, returning to the hospital only for regular monitoring. After a week, he was down five pounds and feeling good. His vitals checked out, blood pressure was normal, and though he had lower blood sugar than most men, he didn’t seem particularly impaired by it. The experiment continued… for 382 days.

Yes, AB fasted for 382 days, drinking only water and taking vitamin, potassium, and sodium supplements. All told, he lost 276 pounds, reaching his target weight of 180 pounds and maintaining the bulk of his weight loss. Over the five following years of observation, AB regained just sixteen pounds, putting him in excellent, but underpopulated territory (at least 80% of dieters eventually regain all the lost weight). Other doctors paid attention. Maybe it was the fact that it was the 60s, and all sorts of crazy stuff was going on – rebellion in the air, good music being made, a war in Vietnam, Ken Kesey and his Merry Pranksters blazing across the U.S. in a beat-up school bus, spreading the good weird word, Kevin Arnold and a young Marilyn Manson coming of age in Anytown, USA – but for whatever reason, placing obese patients on extended and short-term fasts became relatively common practice.

But could this work for the average person looking to lose weight without submitting to constant medical observation?

Absolutely. Study after study shows that whatever you want to call the protocol – intermittent fasting, fasting, alternate day fasting, or alternate day caloric restriction – it works very well for weight loss. A few recent ones:

So, yes: it works. But does fasting work solely through caloric restriction, or is it doing something special?

That’s the real question. There’s no question that fasting causes weight loss through caloric restriction. Obviously, when you don’t eat anything, your body turns to its own stored energy reserves, reserves that take up physical space and have mass. Depletion of those energy stores reduces mass and thus weight. Total and absolute caloric restriction. That’s elementary stuff and the studies from the 1960s show that.

To dig a bit deeper, let’s look at how weight loss occurs during a fast. I’ll stick to research involving humans only (sorry, rodent personal trainers).

Secretion of growth hormone, one of the premier fat burning hormones, increases during a fast. In a five-day fasting protocol, men experienced increased GH secretion on day one and day five (the only two days where GH was measured). A later study showed that during two-day fasting sessions, growth hormone secretions increased in both frequency and intensity in men. They experienced more frequent GH bursts and each burst secreted a higher mass of GH. A more recent study found that 24-hour fasts increased GH by 1300% in women and almost 2000% in men.

Fasting decreases fasting insulin levels. The presence of insulin inhibits lipolysis, the release of stored triglycerides (body fat). Without lipolysis actually releasing stored body fat, it’s rather difficult to, well, burn that body fat for energy. During a fast, fasting insulin decreases and lipolysis increases. This insulin-blunting aspect of fasting quite literally allows the fast to be successful, because without the ability to access stored body fat for energy, making it through a period of zero caloric intake will be nigh impossible.

Fasting improves insulin sensitivity. 20-hour fasts were enough to improve insulin sensitivity in men.

Fasting increases the catecholamines, both adrenaline (epinephrine) and noradrenaline (norepinephrine). Both catecholamines increase resting energy expenditure during a fast, and guess where your fasting body finds the energy to expend? From body fat. Catecholamines activate hormone sensitive lipase present in adipose tissue, spurring the release of said fat. This makes intuitive sense, doesn’t it? If you’re hungry in the wild, you need to hunt (or gather, or fish, or somehow procure food) and you need energy to do it. The catecholamines help provide some of that energy while burning fat in the process.

Hmm, notice anything? All those mechanisms dealt with fat burning specifically. While there may be some weirdo out there who’s interested in reducing bone mineral density and muscle mass while maintaining fat tissue, I would wager that what most people mean by “weight loss” is “fat mass loss.” From the stuff I just linked, it looks like fasting burns fat, rather than just weight. But what about Conventional Wisdom which claims that fasting increases muscle wasting – maybe because your body will totally recognize the lethal nature of all that arterycloggingsaturated animal fat and choose to break down muscle instead? Is it true?

Let’s go to the research:

In one study, normal weight subjects ate just once a day without reducing overall caloric intake. Weight didn’t change, which isn’t really surprising, but body composition did change – and for the better. Body fat decreased and lean weight increased (in addition to a bunch of other beneficial changes) without an overall reduction in calories.

recent review of the relevant literature found that while fasting and caloric restriction are “equally as effective in decreasing body weight and fat mass,” fasting is “more effective for the retention of lean mass.”

Conventional Wisdom strikes out again.

In closing…

It appears that fasting “works” in several different ways:

1. It decreases caloric intake. In order to lose weight, you need a caloric deficit. That really isn’t in contention here, folks.

2. It increases fat oxidation while sparing lean mass. Since what we’re trying to do is lose fat (rather than just “weight”), the fact that fasting increases hormones that preferentially burn fat and decreases hormones that inhibit fat burning is extremely desirable.

3. It improves adherence. In most of the studies surveyed, participants found fasting to be an extremely tolerable way to diet, especially when compared to outright caloric restriction. Even AB, the fasting Scotsman, reported very little difficulty throughout his 382 day fast. If fasting is easier for you than trying to laboriously count calories, fasting is going to be the more effective weight – er, fat – loss method.

All in all, fasting is an effective way to lose body fat. It’s not the only way, and it isn’t “required” for Primal weight loss, but many in the community have found it to be very helpful and the literature backs them up. If you’re looking to jumpstart your fat loss, fasting may be just the ticket. To get some ideas, be sure to check out my post on various fasting methods.

In subsequent installments, I’ll highlight some of the other benefits of fasting. There are a ton, and new research is being released all the time, so I expect I’ll have a lot to discuss. Until then, I’d like to hear about your experiences with fasting for fat loss. Has it worked? Has it failed you? Let us know in the comment section!

Thanks for reading, everyone!

Here’s the entire series for easy reference:

Why Fast? Part One – Weight Loss

Why Fast? Part Two – Cancer

Why Fast? Part Three – Longevity

Why Fast? Part Four – Brain Health

Why Fast? Part Five – Exercise

Why Fast? Part Six – Choosing a Method

Why Fast? Part Seven – Q&A

Dear Mark: Women and Intermittent Fasting

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. Hi Mark

    Great article! I fast for religious reasons, it is my second one today (will do 30 in total over a month). I cannot eat or drink anything for 19 hours. I am hoping to lose weight during this month and maybe continue doing a ten hour fast (but drinking water) after this month of religious fasting has finished. Would doing aerobic exercise such as the rowing machine be beneficial whilst fasting? Also, is there a particular time in the fasting day that would be the best time to exercise? At the moment I’m breaking my fast at 9.30ish

    Shabnam wrote on July 22nd, 2012
  2. Managed a water fast for 19 days several years ago. My appetite dropped out after about three days making each day easier. Had interesting dreams about mountains of food. Have not seriously fasted since, but comments on this site make me want to try again even if only portions of the day. Have also found helpful weight loss tips at http://thefatlossfacts.com.

    Anita B. wrote on July 24th, 2012
  3. No doubt fasting is one way to reduce and you have correctly dispelled some myths about it. However, I have some reservations as whether it work for diabetics. This can prove to be dangerous as sugar levels tend to drop or rise suddenly of fasting.

    Recently I have come across 3 weight loss products that approach the problem differently.
    The main issue that they tackle is that you become what you eat. If only, the food that you eat could restrict the fat and flab, wouldn’t it be just great?

    Well, these three weight loss products do just that., naturally. Using natural products and a totally different way to tackle the flab, they ensure that you become slim and remain that way!!

    I recommend you give them a fair try.

    Kishore Kowshik wrote on July 30th, 2012
  4. I don’t agree with you one bit. Isn’t it a fact that if you fast you gain weight instead of lose it? Go here to find out how you can truly lose weight best3diets dot com

    Vanessa wrote on August 18th, 2012
  5. love your post.I don’t know anything about the primal diet or IF.I am interesting in taking on this challenge.Can you provide me with more information on how to begin this journey.It sound fascinating.I am trying to loose some weight and increase my energy.

    Patricia wrote on September 3rd, 2012
  6. In 1997 I undertook a 40-day fast for spiritual reasons. I had absolutely no concept of Primal eating or lifestyle. After the fast I returned to normal carb-centric eating and put on all the weight very quickly, about 30 lbs. I repeated the fast every year for about six years. In those days i allowed myself the ocassional juice or starbucks latte if i was feeling weak. Here’s what I experienced physically (aside from my spiritual goals):
    1. It was was relatively easy.
    2. Hunger goes away the first or second day
    3. Counterintuitively, my energy levels would rise. I found that I wanted to run everywhere. Upstairs, outside (I was not a runner by any means and was still about 30lbs overweight)
    4. I slept better
    5. There was no decrease in mental sharpness (I design electronic controls for mission-critical applications)
    I gave it up for family-sociall reasons. Then in 2005 I felt “called” to fast again. This time I allowed myself 50 days to complete a 40-day fast. That is, I allowed myself 10 “eat-days” to accommodate family and social events. I liked this lifestyle so much that I repeated it every month from March until September. I lost 50lbs and never felt better.
    I thought that I had arrived, but now in retrospect I can see that I was a carb-addict and despite my marathons, and iron-man (v70.3) triathlon racing I was still a compulsive over-eater of carbs. Weight gain is just too easy for me when there is bread, potatoes, beer or pasta involved. To gain 30 lbs in a year is not a problem for me.
    Now, having researched and investigated and gained a much more solid understanding of paleo and strength training I have begun another long-term fast. I started 5 days ago and have allowed myself only tea (sorry, one vice I cannot live without) and lemon-water. I will inject “eat-days” full of meat and veggies every 8 days or so to make sure that the family & friends social structure is not greatly impacted.
    Bottom line, I never feel better than when I am
    Fasting.

    Bob Tonner wrote on September 4th, 2012
  7. In addition to intermittent fasting I’ve found doing yoga has been a great way to help lose weight. It relaxes your body and mind. It can help with detoxification because being overweight may be a sign your body is high in toxicity. Yoga also helps release stuck emotions because being overweight usually has an emotional component that we need to be able to address.

    Jen wrote on September 9th, 2012
  8. Wondering about the effects of fasting and injury recovery. I have been living primal for roughly a month. I am an athlete, recovering from anterior tibial stress fractures. They are healed, and have been for several months, but I flare up the fracture site very quickly with activity. I’m being more aware of sleep, and trying to get more of it because I don’t think my body is recovering as completely as it could at night. My nutrition is good, and I’m feeling body wanting to fast, and this was not the case before going primal. Any thoughts on fasting and injuries?

    Katie wrote on September 9th, 2012
    • That’s an interesting thought Katie. A few years ago I had a shoulder operation to repaid a torn major pec muscle. I was using intermittant fasting during my rehab to manage weight and stay lean as no exercise was possible. Wish I had kept a diary on the condition during these fasted periods… perhaps the reduced inflammation aids recovery

      Luke M-Davies wrote on September 10th, 2012
  9. Wouldnt it be nice if someone actually did, or cited a research to finally put to rest, what burns when we fast – fat or muscle.

    Clearly there are two theories here with equal # of proponents – they agree up to glycogen depletion, but then there’s a fork in the road. One side thinks that fasting will take us to starvation/ hibernation mode and it will be harder to lose fat, and muscle will burn to fuel the body. Authors like Taubes have said that fat is a selfish tissue and when it sees caloric restriction it becomes bigger and bigger.

    The other side says that fasting will induce lipolysis – that is, will dig into fat cells. That forms the basis of concepts like IF and Glycogen Depletion.

    These are opposite, and contradicting theories. Body cannot be holding on to fat tissue and burning muscle, AND burning fat tissue at the same time.

    Which one is correct – please help! I hope we realize how important it is to determine that unless we’re ready to do things like Fasting and burn even more muscle. Point us to some authentic reference for this question. Thanks.

    Jazz wrote on October 3rd, 2012
  10. Do you know muslims spend an entire month fasting? It’s an obligation of Islam for the health of body and soul. Intermittent fasting is great for the soul too..

    Lila wrote on October 4th, 2012
  11. This is a cheaper & healthier way of losing weight. Am willin to try it out. Thanx

    Maru wrote on October 21st, 2012
  12. Im reading Vincent Ng’s book TEN, lean and sculpted body in ten weeks (anyone familiar with it?)

    He(his research) says that one should not eat less than 1000 calories a day, since our body will switch to starvation mode, which slows down our metabolism.
    When you eat less, your body will slow down its metabolic rate, allowing you to last longer without food.
    Another critical reason why we should not allow our bodies to lapse into starvation mode is that the body will attack the lean muscle tissue as it consumes most calories. When you lose lean muscle tissue you will find it more difficult to lose body fat.

    So on the subject of fasting, how big is the effect of the above to any of the fasting methods in which we would apply?

    Ronny Jansen wrote on October 29th, 2012
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    Keith wrote on October 29th, 2012
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    Brock wrote on October 31st, 2012
  15. Wow, 382 days without food? 24 hour fast is good enough for me. Thanks for a great article on fasting.

    Wayne wrote on November 9th, 2012
  16. See the video I recently did about the ideal time period to fast for maximum fat-loss. Hope this helps some of you out! :-)

    http://www.youtube.com/watch?v=FnjJTVGA_yM&feature=share&list=UUN3PpCtqfVBbcfSZw0kKwgQ

    Dean Bocari wrote on November 19th, 2012
  17. A powerful share, I simply given this onto a colleague who was doing slightly evaluation on this. And he in fact purchased me breakfast as a result of I discovered it for him.. smile. So let me reword that: Thnx for the deal with! But yeah Thnkx for spending the time to discuss this, I really feel strongly about it and love reading more on this topic. If doable, as you turn into experience, would you mind updating your blog with more details? It’s extremely useful for me. Massive thumb up for this weblog put up!

    bit.ly/QyrES8/ wrote on December 4th, 2012
  18. Um…. WTF? Is everyone here stupid… “Yes, AB fasted for 382 days, drinking only water and taking vitamin, potassium, and sodium supplements. All told, he lost 276 pounds, reaching his target weight of 180 pounds and maintaining the bulk of his weight loss”

    Does no one here realize, that wouldn’t work… There is a reason why you need to take food in regardless of what your body size is… I would know… I was anorexic long enough to know the effects. First of all, with out an input of essential amino acids, say good bye. Your enzymes with be recycled to a point, but you will eventually die.

    I’ve been anorexic. I know how fast you loose weight, especially if you are drinking zero calorie fluids. Now the important thing is, you can get glucose from glycogen… you can make glycogen from glucose, and other saccharides, but you can’t make them from acetyl Co-a… which is essentially the energy source from fatty acid metabolism (Beta oxidation). The fat provides a lot of energy (ATP) so your body can survive, but that doesn’t matter. Your body always needs an input of saccharides in order to make your muscles go… Muscles don’t work on FA catabolism, they work on creatine phosphate, glycogen, and glucose. This man would eventually completely deplete his stores of glycogen/glucose long before 276 days resulting in death. Without glucose, your muscles just don’t work…

    braeden wrote on December 23rd, 2012
  19. I find that sometimes I “automatically” fast. I’ve gone an entire day without eating simply because I am not hungry.

    I started eating primal and began hiking about 8 months ago.

    I’ve lost 50 pounds and I’m now at a very good weight for my build. It was the easiest weight loss I’ve ever experienced in my life.

    Rich wrote on January 16th, 2013
  20. thank you for such an insightful article. I would like to share my experience with weight loss and fasting. After giving birth to my first child, i gained 20 kg ( was only 50 kg pre-pregnancy).. i tried all sorts of dieting methods but i could not stick with it long enough. so i fasted for a month (I am a Muslim by the way, fasting is compulsory in Ramadhan). I managed to lose 10 kg from fasting 30 days. afterwards i did gain weight, but only 1 kg. i checked at the hospital and i am healthy. so i would say that fasting really help me shed all the extra weights.

    ruby wrote on February 26th, 2013
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  23. I have fasted for 9 days (only water) to cure my pancreatitis and I’ve lost 7-8 kg. I work out and I didn’t notice any muscle mass loss. I experienced many positive effects like improved health, faster metabolism, healed wounds and my acne just disappeared. I also practice 2 or 3 days fasting and when I get sick I fast for 24 or 36 hours untill I feal well again – it works perfectly!

    Kristina wrote on March 11th, 2013
  24. You actually make it seem so easy with your presentation but
    I find this topic to be actually something which I think I would
    never understand. It seems too complicated
    and extremely broad for me. I am looking forward for your next post, I will try to get the
    hang of it!

    Moses wrote on March 12th, 2013
  25. I would try a cleanse in addition to all of this.. I did a detox from sugar which was a great kickstart to the new healthy life choices I was making!

    good luck and stay strong !

    cali wrote on April 9th, 2013
  26. I have been attempting paleo for the past year. Physically and mentally I see major positive changes. The difficulty arises because I have an income of six hundred dollars a month. I have tried and simply cannot afford to live paleo. I run out of food at the end of the month and go to the food bank which is like carb nirvana. So finally I compromised and added potatoes and rice to get through, with obvious drawbacks. But the fasting might be exactly what I need to stay on track and get through the month. I appreciate the information.

    Lisa Carlson wrote on May 24th, 2013
  27. I have done quite a few water fasts in the past 33 days was my record before the fast I just finished which was 59 days. I studied the process in great depth and read all the research before I attempted the first one. I was well aware that this in not a new therapy. It has been done safely for thousands of years. The body know how to fast and it competent and well versed in just what to do if we stay out of the way.

    I lost 63 pounds and 14% Body Fat. I have been off the fast for 2 weeks now and have gained back some weight (bone, muscle, water) but have not gained back any body fat. I feel great and I just turned 60 years old. I know that during those 59 days my body did a lot of breaking down and recycling of old and diseased tissue, viruses, bacteria, fungus, etc. Nothing is ever wasted when a person gives the digestive system a rest. I think the key to fasting is to relax and let the body take over. Eliminate as much stress as possible and enjoy what is taking place inside your body. Feel all the good things that are going on and surround yourself with positive, supportive people. Read and study everything you can about fasting and think only positive thoughts. My fasts are always times of great peace and encouragement to me.

    Joan wrote on June 27th, 2013
  28. I read the article and related comments. In my opinion the article explained clearly how fasting can help the body for fat lose, however, the article lacks more details about the best way of fasting, how long, how to start and end your fasting and so on.. Etc.

    I am fasting now… it is Ramadan and we have 30 days of fasting starting from early morning around 4 AM till sunset around 7-8 PM (this is summer time, and in winter times the day will be shorter, and therefore the fasting hours are less). During fasting period nothing will enter your mouth till the end of fasting in your day when you can eat and drink anything you want. Notwithstanding to maximize your benefits of fasting you have to be careful of your food….. its a golden chance which comes once every year to change your habits and change your life.

    in all cases, if you wish to explore more details about fasting and how it can be done for best results please contact me or visit any of websites about Ramadan and fasting.

    Thank you

    Advocate Khaled wrote on July 13th, 2013
  29. If anyone is interested, I’ve put together a video debunking the top 6 most common myths surrounding nutrition and getting in shape… I would love to hear feedback from this community as I plan on continuously adding on to it as I learn more, you can check it out here: wisdom-square.com/how-to-lose-weight-and-belly-fat-fast.html.

    Good luck to you all! :)

    David Alsieux wrote on August 8th, 2013
  30. i think if want fasting weight loss. you need do every day more and more hard to loss weight

    hannlam wrote on October 4th, 2013
  31. Looking over the comments most people are either curious about IF or hav had good luck with it. Those that are skeptical seem to have a rant and point to references apparently supporting their viewpoint but say little about their experience. I would suggest that they try it and see what their direct experience is before they decide which line of evidence they wish to follow.

    I’m generally pretty clean on my diet yet fasting for 16 – 24 hours 2 days a week helped be drop some bodyfat and seems to have improved my energy levels. Just my experience

    Jake wrote on October 31st, 2013
  32. For me, the key was lowering the amount of fat in your diet. That was what I noticed. Also, the normal thing is doing exercise and physical activity, along with eating fruits and vegetables. Here is a great way to see how healthy eating will benefit you: http://maintainingyourweightloss.com/lose-weight-now/.

    Kareem wrote on November 10th, 2013
  33. Just remember that anorexics tend to eat almost nothing all the time…

    Nabil wrote on November 17th, 2013
  34. Mark your article on fasting is fantastic. Is easy to read and understand,makes a lot of sense to me. On reading the comments it seems that fasting works. Great site. Have you seen this site?.lose leg fat

    Diane wrote on January 21st, 2014
  35. This guy looks like he pees on peoples butts and then drinks it with a straw. Do you really want diet advice from a piss drinker?

    Peter wrote on February 2nd, 2014
    • Really? You sound so mature!

      Ashley wrote on February 2nd, 2014
  36. Its a no brainer really when one thinks of the cave man or Grok he caught his meal, had a big “nosh” up and then didn’t eat until he caught his next meal. Man has been doing this for quite some time until the advent of the 3 square meals a day put out by the people that need this to further their businesses. I believe that Man has had thousands of years to fine tune the Grok way until the “smartypants” came along and stuffed it all up. So for my money fasting is the way to go, this link is interesting to watch:
    http://www.wgbh.org/programs/Eat-Fast-and-Live-Longer-With-Michael-Mosley-2221

    bert wrote on February 23rd, 2014
  37. Hahaha, I read this article a few years ago, and until today I had thought that he ate an apple a day throughout the fast… It appears the brain works in weird and wonderful ways :)

    Fraser wrote on August 15th, 2014

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