Is Intermittent Fasting Healthy?
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.
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Posted By: Mark Sisson
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.
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.
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.
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.
Congratulations Scott, That is wonderful. May I ask what kind of foods do you eat when you break your fasts?
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.
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?
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.
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.
IS there a difference of how the weekly fasting effects you if you younger like 15, if you skinny or fat?
And is your a boy or girl
ME and my friend want to do an experiment of our own on the subjected, does anyone know any experts we could talk to?
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.
Cheers
George
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, 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 http://www.trackyourplaque.com/blog/2011/05/bet-you-cant-fast.html You could email him.
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?
Thanks
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.
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!
I’m not sure if this has been mentioned, and it may be a bit technical, but here goes. I keep hearing people referencing a fast for “24 hours” and then they eat dinner one night and nothing until breakfast two days later. That’s probably closer to 32 hours. If you want to fast for 24, as I have tried with good results, you can eat dinner one night, and then dinner again the following night. Assuming you eat at the same time – those are 24 hours apart. I’ve found that is actually fairly easy to do, possible sneaking some nuts or soybean seeds if I really get hungry during the day.
II am doing Paleo and only eat about every 4 or 5 hours and eat three meals a day with my last meal around 5pm. I am never hungry between meals anymore.
Is it possible to just skip a meal for a fast? Would that be even close to being effective???
D
Let me get this straight,
1) Fasting causes increased insulin sensitivity.
2) Eating a lot causes decreased insulin sensitivity.
So if we keep fasting once in a while, in the context of not binging during days with food, then we improve our insulin sensitivity, which would allow our bodily cells (including adipose cells) to be more responsive to insulin.
Therefore, we will get fat once we do this because our fat cells are more sensitive to insulin, and is able to uptake more glucose?
Confused. How is this going to help promote fat-loss and prevent muscle-loss?
By accident I did a 23 hour fast and found it to be not a bad experience at all. I had breakfast and then didn’t have a chance to eat dinner. I felt so good doing this that I decided to try doing it once a week.
On my fast days I eat an all-meat breakfast (1 egg, 1 beef patty and bacon the last time). Then I do not eat until breakfast the following day. I feel great, alert, strong, energetic and mentally calm. Now I can go to my evening jam session and jam all night without worrying about getting home to make dinner.
Peter I think this promotes fat-loss and prevents muscle-loss because you are still eating every day. You aren’t starving. You are simply increasing the window of not eating which allows other hormones in your system to do their thing. I think it is part of the process of improving your metabolic flexibility, something lost eating the SAD with frequent feeding times.
Our fat cells will become more sensitive to glucose which will keep the insulin levels steady. We won’t need to consume so much food that floods our system with glucose. Just enough to keep the insulin stable. Now that I have been fasting, my glucose levels stay within the 75-97 range.
I have been vegetarian since 94 and vegan since 04. I have always stuck with 5-6 small meals a day and done well. If I waited longer I would start getting a headache, telling me I need to eat. Recently I stared the Candida Diet mainly to support my wife who really needed to. In the process I found out that I literally had a wheat addiction that would cause headaches if my levels got low. Since kicking wheat (and corn and sugar) when I get hungry I don’t get a headache any longer. This has enabled me to fast for 24 hours with little discomfort and actually enjoy the sensation of calorie restriction. I plan to soon begin an IF program using the daily 16 hr fast, 8 hr eat method and include a basic muscle building routine. Wish me luck!
Good article Mark.
I have at least 8 years coaching people using IF methods and have found a 12-14 hour fast to be ideal in most fat loss situations. Given this I have my clients do a 3 day system where they eat a large meal mid-morning and another late at night. The next day they eat between 1-4pm and have only water the rest of the day and day 3 mirrors day 1. It’s worked quite well at breaking plateaus in my weight loss clients over the years and I continue to use it today.
On another note one area I am extremely interested in but see little research on is the idea of food batching. It seems to me that ancient man grew, found or killed something and probably munched on that food or few foods until they were gone or nearly gone. So, if fish are prevalent this week, we catch a bunch and eat tons of fish….then they leave. Next week berries are ripe and we kill a deer so we eat berries and deer for 18 days straight before we catch a wild pig and find some nuts which may last us a couple of weeks. I’ve played with this a bit on my own eating just 3 foods each day for up to 2 weeks before changing foods and beyond being really boring, I actually felt pretty damn good. Thoughts on this concept?
Jared, as to your comment on food batching. It makes lots of sense to me. I don’t do food batching, as you describe, but I do find myself eating the same thing for days without becoming sick of it. When I do become sick of anything I eat, I quit eating it. I eat once a day, now.
Great issues altogether, you simply received a new reader. What may you recommend in regards to your put up that you made a few days in the past? Any certain?
I am a wrestler and in my fasting experience i had to drop about 7 pounds and still be hydrated to be able to wrestle at a certain weight. I did a fast starting Monday night and ending Tuesday night. When i woke up in the morning 1 weighed 154 lbs. All day i drank water and ate nothing. I then weighed 150 lbs so i still had to drop 5 lbs so i ran with lots of sweatshirts and sweats on. I got all the way down to 142 lbs in less than a hour.i then drank 3 pounds of water to make sure i was hydrated. i took the hydration test and passed and weighed in at 145 lbs. After that day my natural weight was 148 lbs by eating and drinking anything i wanted to. Fasting helped me lose weight quickly and keep it off!
Quick question…
Water whilst IFing obviously great – still or sparkling. But is coffee ok too? Black coffee? Seems too good to be true!
Cheers
Read “How to Eat to Live” by Elijah Muhammad this book was written in the 60′s. He talks about fasting for 24 to 48 hours and how eating this way will prolong your life.
Thank you for making this post.
Actually, as a Muslim, fast is obligatory during 30 days at a certain period of the year, from dawn to sunset.
I did not know about the finding you mentionned in your post about the benefits of fasting. However, I think that not eating for a good period could help better appreciate the food that one has.
Moreover, if a person is fasting for the Ramadan for example, it helps to avoid eating whenever you feel hungry (except after the set time for breaking the fast). Thus, there is an element of self control.
Thank you for sharing these data.
I fast from 11pm-1pm daily. It is working wonders for me. Energy through the roof, gaining strength, burning fat, always in a good mood and caloric management has become a breeze. Counting calories is practically pointless. Quite difficult to eat too many calories in the small 10 hour window.
My experience: Since cutting sugar out of my diet, for the most part several years ago, I naturally started skipping breakfasts and kept weight I had lost – off. Giving in to the idea that it is important to eat breakfast saw me gaining weight back. So I skip breakfast most days. (Sometimes I do eat breakfast, but it is usually when I know I won’t have access to good food for most of the day.) My habit for the most part is to go from 7pm to about 11am to 1pm without eating. That is 16 to 18 hours. This is before learning about primal/paleo eating.
Although, I still have a few pounds to loose, most people don’t believe that I am 50 years old. I look and feel healthy!
I don’t know if this has been mentioned already. THis is TMI, I know but it is very significant. My bowel movements have improved immensely. I ‘go” regularly everyday. I empty my gut about an after after my fast-breaking meal. I sometimes “go” even twice on some days. Nothing is healthier than regular BMs.