One of the well-known rules of weight loss asserts that when you eat is as important as what you eat. Which is why many of us have long held to certain food-timing conventions we believe will help keep our metabolisms humming from the moment we wake up: We kick-start our mornings with a solid breakfast; we eat several small meals throughout the day. We try not to go more than a few hours — heaven forbid a whole day — without food because we fear it might slow our metabolic rate to a crawl.
Now, though, a small-but-growing group of nutrition and fitness experts is beginning to question that conventional wisdom. These experts argue that constant grazing can actually disrupt metabolic pathways and that the best way to kick our metabolisms into high gear is to occasionally eat less often — in short, to observe an eating pattern known as intermittent fasting.
When most of us hear the word “fasting,” we’re likely to think of politically motivated hunger strikes or endurance stunts like illusionist David Blaine’s infamous 44-day stint, sans food, in a transparent, Plexiglas box. But the occasional fasting these experts are recommending is something different. They point out that humans evolved through multiple short-term periods of caloric restriction, and that our metabolisms operate more efficiently when freed from the burdens of 24/7 digestion and nutrition assimilation.
The time frames recommended for intermittent fasting vary. Popular options (all of which can incorporate sleep time) include daily 14- to 16-hour fasts, once- or twice-weekly 24-hour fasts, and alternate-day fasts of assorted time durations.
Ultimately, the goals and results of these programs are similar. Studies indicate that short-term fasting can increase longevity, help regulate glucose levels, and help treat everything from asthma and autoimmune diseases to cardiac arrhythmias.
In many ways, short-term fasting has more in common with detox regimens than with extended fasts of multiple days or weeks. But detox programs follow specific dietary rules, while short-term fasts rely on only the period of not eating to achieve health benefits.
It should be noted, however, that some health experts, including detox experts, are not big fans of intermittent fasting. (For more on that, see “Fasting vs. Detoxing,” below.) And even advocates acknowledge it’s not for everyone (see “Note,” below).
Integrative nutritionist Kathie Swift, MS, RD, LDN, has mixed feelings. On the one hand, she notes, observing what happens to the body during a short fast can help people become more observant of their habitual pattens and learn to identify real hunger.
“I’m fascinated by the idea of alternate-day fasting,” she says. “Some people do that almost intuitively — eat heavily one day, and then really, really cut down the next day.” But she also notes that because the body relies on key nutrients to eliminate toxins, build healthy tissue and more, intermittent fasting can cause problems for people who are not generally well nourished.
The biggest skepticism about fasting stems from the concern that it will disrupt metabolism and lead to weight gain. Yet a new study published this year in the journal Cell Metabolism suggests that limiting periods of food intake to eight hours a day might reduce the risk of obesity and obesity-related diseases.
In the study, researchers noted that mice who continually grazed on fatty food for 100 days gained weight and developed high cholesterol, high blood glucose and liver damage. The mice that fasted for 16 hours a day — but ate the same total amount of food during their nonfasting periods — weighed less, stayed healthy and performed better when they exercised.
Why? Researchers have found that after a few hours of fasting, the body starts to burn fat and break down cholesterol into beneficial bile acids — as if it were flipping a fuel-selector switch. The liver, meanwhile, shuts down glucose production for several hours, lowering blood glucose levels. Instead of ending up in the bloodstream, extra glucose is used to repair damaged cells and make new DNA, which can help prevent chronic inflammation. Meanwhile, liver enzymes are activated and help in the creation of brown fat (the good kind, which converts extra calories to heat).
“You’re enhancing your body’s ability to use fat as an energy source,” says strength and conditioning specialist Mike T. Nelson, a PhD candidate at the University of Minnesota in kinesiology and an intermittent faster. “Being more metabolically flexible allows you to shift back to burning fat faster after a meal.”
Frequent eating, on the other hand, means the body keeps making and storing fat, enlarging both fat and liver cells. Take that too far, and liver damage can occur. Plus, the liver keeps right on making glucose and raising blood-sugar levels.
Beyond Weight Loss
Many intermittent fasters report experiencing something not often associated with calorie restriction: relief. Those who have struggled with trying to eat five to six meals a day (or to count calories) report feeling eased of those burdens. Intermittent fasters also say they have more patience around food, and a stronger preference for eating high-quality fare on nonfasting days.
“Eating six meals a day can train you to get hungry more often,” says strength coach John Romaniello, founder of Final Phase Fat Loss. “Once you start practicing some sort of fasting, you usually eat less on nonfasting days, too.”
Fitness enthusiasts have discovered that fasting makes exercising for fat loss more efficient, and, in turn, exercising makes fasting easier. “Athletes performing long endurance activities while fasting actually burn more body fat than athletes who are fed (because the fed athletes are burning through food energy before they get to the stored energy in their body fat),” writes fitness guru Brad Pilon, MS, in his e-book, Eat Stop Eat (Strength Works, 2012). “The very act of burning fat also releases something called ‘glycerol’ from your body-fat stores. When the fatty acids are released, so is the glycerol. Glycerol is a valuable precursor for gluconeogenesis [a metabolic pathway] in the liver that helps keep blood glucose stable.”
If you tend to get hungry before working out, Pilon notes that the sensation might be more psychological than physical. “Most likely, what we call hunger is really a learned reaction to a combination of metabolic, social and environmental cues to eat,” he says. “Consider that most people get noticeably hungry or irritated if they have gone more than two to three hours without eating. But during this time, metabolically speaking, they are still in the fed state.”
While the case for fasting as a general-health tool is compelling, the case for fasting as a longevity booster may be even more compelling. Studies have shown that severely restricting calorie intake can increase the lifespan of rats and mice. (Data published this year in the journal Science Translational Medicine showed that mice with cancer improved their survival rates when they fasted during chemotherapy.)
The National Institute on Aging announced earlier this year that fasting for one or two days a week may also help stave off Alzheimer’s, Parkinson’s and other degenerative brain conditions. When fasting, the researchers said, brain cells are mildly stressed, benefiting the brain in a similar way to how the mild stress of exercise benefits muscles.
How to Get Started
Several well-regarded experts recommend fasts of a day or less, but you can start with whatever seems doable and appealing to you. Pilon, for example, advocates a 24-hour fasting period, one to two times per week. If you spread the fast over a two-day period, he points out, you can still eat every day — and sleep through the hardest part.
“Depending on your schedule, and what you’re most comfortable with, you could do a lunch-to-lunch or dinner-to-dinner fast,” Pilon says. “Going longer than that is very intrusive on life. Really, what I’m asking people to do is not fast, but take a break from eating. You learn patience, and that you don’t have to eat all the time.
Once you know your muscles aren’t going to melt, your metabolism is not going to crash, you regain the ability to be patient when it comes to eating.”
Pilon also likes this method because it allows him to eat food he loves at socially appropriate times: “I’d rather have dinner with my wife and kids than eat by myself all day at work.”
If a 24-hour fast is not your style or seems too extreme, Swedish nutritional consultant and personal trainer Martin Berkhan advises condensing your nutritional intake into an eight-hour period to maximize potential hormonal benefits. The idea behind his 16-hour fast works on the theory that you produce growth hormone when you sleep. Once you start eating, the spike in insulin shuts it down. By avoiding food in the evenings, and pushing the first meal of the day back, you may be able to maximize growth-hormone production.
Romaniello has even developed a system that allows for cheat days: You eat whatever you want throughout the day (he usually splurges on wings and burgers), then fast for 36 hours, and then eat a balanced diet during the week. Similar to Berkhan’s idea, Romaniello’s belief is that leptin (the hunger hormone’s counterpart, which makes you feel full), gets bumped up after the cheat day.
Whatever the method, many people who thrive on short-term fasts like them for their simplicity: You’re either fasting, or you’re not. No counting calories; no restricting certain foods. But, as in all things, practice in moderation until you’re able to gauge exactly how intermittent fasting affects you physically and emotionally.
“You have to keep it in check,” Pilon says. If you’re missing out on a lot of life events or stressing over foods because of your diet, then it’s time to detach, relax and reassess.
Sheila Mulrooney Eldred is a Minneapolis-based health-and-fitness writer.
I’m a recovered Bulimic and 8 hour eating has changed my life.
I find skipping breakfast (or in my case I have coffee with a little milk) has totally calmed down my eating. I do not spend all day every day planning meals, snacks and counting calories.
One of the best techniques I learned in recovery from my ED was to practice intuitive eating – but, they said, NEVER, EVER miss breakfast. Well, I never, ever, felt hungry in the morning so the whole concept of a big breakfast went against IE for me anyway. Not only did I not want it, but i felt the huge jump start of energy had me swinging between bright eyed and sleepy. Eating became a constant juggle of calories and timings throughout my whole bloody day.
I now eat my first meal of the day at 12 and eat dinner before 8. If I’m hungry before 12 I eat. If I have a social occasion I shift my timings a little. My energy levels are so much more constant. My cravings have subsided considerably.
I don’t feel that this is a diet. I feel this is just a different approach to eating. I eat plenty of calories (I stop counting a while ago, but was averaging the same 1800-2200 a day).
I can’t recommend it enough. I don’t care about the weight anymore – I have no idea if I’ve lost any, I don’t think it would be much. I care about stabilising of my blood sugars and as a result my cravings. That has been the god send that is 16/8 eating.
I’m getting my bloods done next week and I can’t wait to see the improvement.
I just wanted to place my personal experience with IF in here. I did what is probably universally NOT recommended and began IF while in an active eating disorder of bulimia nervosa (also, a former anorexic). I feed from 12 to 6 or 8 pm, depending on the day, and fast either 16 or 18 hours. I found that this released me from the pressure cooker of guilt when I ate and the subsequent purge. If I want pizza, I have it because it’s allowed in my window; usually I would have purged that right up out of guilt. Same goes with ice cream or any other of my previous list of fear foods. What I have found with IF is that my body is actually craving whole foods like salads with snap peas and avocados, baked salmon and wild rice, greek yogurt, etc. I find my fullness cues are regulated and it takes far less food to make me full, reducing my urge to purge. I feel the freedom to eat healthy but not due to ED pressures but rather by my body’s direction. I also have the mental freedom to indulge, go out to eat and not punish myself by purging because I know I eat well the majority of the time. IF has changed my life for the better. As someone who has a history of purging 11 times a day, I’ve only purged twice since I started IF many months ago, and those times were when a significant emotional event occurred. IF has been a godsend, and furthermore, I was slightly overweight when I started IF and have since lost about 20 lbs and am now safely and smartly in my healthy weight zone and with a much better self image. So, that’s my experience with IF and I gotta say I’ve never been happier or felt better.
In India the two oldest religious traditions (Sanatana Dharma or Hindu and the Jain) emphasize the importance of ritual fasting. There are regional and other variations. Fasting through the day on saturdays or mondays, followed by a light evening meal of fruits and milk is common. during certain religious festivsls like Navarathri it is common to fast for the 9 days with a light meal in the evening. Fast are prescribed on certain fstival days as well.In other words a fast is never more than a day. It is therefore intermittent.
Pushing aside the religious believing, I want to share some Islamic rules which I think is related to the topic discussed in this article. I am a Muslim.
In Islam, there is a Mandatory rule for Fasting for the whole Ramadan month as per Arabic Calender.
Rules regarding the fasting is such as, “You should eat before Sunrise, fast for the whole day and break your fasting just after Sunset.” In the mean time of fasting you should not Eat nor Drink Nor Attend in any sexual intercourse. And the most popular method in Islam for breaking the fasting is having some Dates.
Now if we look at the benefits of fasting.
At first ‘Rising up early’ which is definitely healthy. You can start early do your intellectual works with fresh mind inhale fresh Oxygen etc. If rising up early is not good then there will not be this rhyme “Early to bed, Early to Rise, Makes a man Healthy, Wealthy and Wise”
Secondly, I don’t have to say about the benefits of fasting for almost 12 hrs you can look up to your own article.
Thirdly, as per research Dates is the tor fruit containing all kind of nutrition possible to present in one single fruit. If someone eat some Dates he will not go on shortage of nutrition. Besides he is also going to have some regular food. but not in large quantity. As there is another rule (habit of Muslims last prophet Muhammad pbuh) regarding eating is that ‘One should wisely eat according to his stomach size. Eat food to one-third volume of your stomach, drink water to one-third volume of your stomach and leave empty to one-third volume of your stomach.’
Lastly, we Muslims have to say our prayer 5 times a day. One before sunrise, one at mid-day, one at the end of the day, one after sunset and one after around 2 hrs of sunset. Muslim men have to say their prayers in Mosque. Far away mosque is encouraged. If I see in this matter I can see some health benefits. you have to walk your way to mosque 5 times a day (walking exercise), say your prayer by following some rules (steady and slowly Standing, bending, sitting, getup etc.). I think it helps a lot for a good health.
And once again for which I have started to write at the first place is that,
There is also a rule in Islam which is “Not Mandatory but better & encouraged” to Fast according to same rule above at Monday & Thursday of every week. Which’s benefit now a days You guys and scientist are starting to realize after long research. We obedient Muslims are doing this ‘Intermittent Fasting’ for 1400 years. Though I didn’t know about the health benefits for this ‘Intermittent Fasting’ but, thanks to you guys for reveling the scientific fact about our fasting. It seems to me now that every rule in Islam is meant for better life.
We are also forbidden to have Alcohol, Pork, Meat of wild animal which hunt by their Claws and those product which is addictive & lose your self consciousness. I hope you must agree these things are bad for a good health and social life.
Just to share. Don’t take it other-wise. Thanks,
Hafij-us-Sayeed
tons of scientific studies of mice have proven to help humans; do a little more research and you’ll discover plenty of examples. As someone trained in exercise physiology, I’m surprised… you seem so dismissive.
if someone has an eating disorder, they definitely need to deal with that on an emotional/behavioral level. I agree that someone like that might not be the best candidate for fasting, but that doens’t mean the concept is invalid. I’m not confident that enough research is there overall, but the bit about the breakdown of fat is rather fascinating.
I know a lot of people who’ve gone on a cleanse or fast, saying it’s for health but a lot of the time they just want a quick way to lose weight. When they got off the fast, they gained the (water) weight back and then some.
I think you lose somewhere between 1-2Lbs of water/fat everytime you fast for 24 hours. If you think about the science of how many calories you have to burn to lose a pound it makes sense.
3500 calories = 1 Lb of Body fat.
Say you are me and you body uses about 2600 calories on average a day/24hrs to maintain muscle, organs, brain, etc.
If I fast for 24 hours and pick back up with normal eating I would have lost about 2600/3500lbs~.75lbs of fat.
The water I would have lost would be whatever extra weight I lost over the .75lbs due to, I believe, the lowered insulin production/blood sugar.
The problem with most people is after the 24hr fast, they binge and redo what they undid.
I’m no health expert (although I did get my degree in exercise physiology), but in my opinion, saying that fasting can be healthy for you, even on a scaled down level as mentioned here, is like saying that exposing yourself to radiation at a level slightly more than the average is healthy.
It’s basically promoting an activity that is widely used by individuals with eating disorders (not healthy), and saying that in small doses you can do your body good (you can’t). Not to mention, it is a very slippery slope. I can imagine that many people who subscribe to Experience Life have been victims of yo-yo dieting and gaining and losing the same weight over and over. You deprive your body of nutrients and you will end up with a binge (another form of eating disorder). This is exactly what fasting can lead you right back into, and what many Americans are extremely vulnerable to.
Also, you mention in this article a study about mice and fasting in relation to longevity. Here’s a wake up call- HUMANS ARE NOT MICE. How about searching for studies that support how fasting and severely restrictive caloric intake increase likelihood for later developing an eating disorder, depression, anxiety, etc… That all lead to decreased life span (see the Minnesota starvation study).
In all honesty, I am surprised to see something like this coming from what I had thought was a well educated form of media. I have read many other examples published by Experience Life that follow the model of “all things in moderation”. This was disappointing to read.
This is very interesting to me. Not to discredit your input because of your degree in Exercise Physiology but what exactly is your authority besides pure opinion?
1. Studies in rats are found to be very widely accepted. No one said humans are rats or vice versa but because of their generally short lives its possible to study something that would happen in a human over a 10 year period in a model that takes 100 days or so.
2. Dr. Layne Norton (has a youtube: Biolayne) did his thesis in protein synthesis and found rats to be very useful. He specifically states that they are very good models for tests like this in his youtube blogs. I think he has a PhD in Nutrition Science or something of the like.
3. I find it interesting that you said that this style of eating is related to eating disorders (I’m assuming you mean ANOREXIA). The opposite of what your talking about is also an “eating disorder” as well which includes continuous OVEREATING which I would say is the polar opposite of ANOREXIA but instead of losing weight you become obese.
4. Most people “INTERMITTENT FAST” and don’t even know it. Most people don’t eat for around 12hrs each day. That could be described as intermittent fasting.
5. Everything you said about “INTERMITTENT FASTING” implies issues much deeper psychologically than what this article means on the surface. The idea of this INTERMITTENT FASTING article is that it can be very good for you. Many, or nearly all people that have done the 16/8 or 24hr say they feel less fixated on food.
6. Try it for yourself before you go bashing it. There is very compelling evidence showing that the health benefits are nearly endless. This simple explanation of INTERMITTENT FASTING shows you this.
7. The best thing intermittent fasting does for us is break us away from the popular SUPPLEMENT INDUSTRY and FITNESS MAGAZINES, which a lot of false nutrition recommendations come from. EATING 100 MEALS A DAY TO BOOST METABOLISM…ENDLESS SUPPLY OF PROTEIN INTO THE BODY. Our bodies systems never get a break and we stay in a FED state much longer.
8. You probably are in a closed belief trap of some kind caused by previous eating habit beliefs.
9. Brad Pilon’s Book specifically states “for healthy individuals”. healthy meaning all aspects: mental, physical, and spiritual.
10. I have been “INTERMITTENT FASTING” for around six months and I feel awesome. I’m around 9-10% body fat @181 and I eat some !@#$ing huge meals. To me INTERMITTENT FASTING is skipping breakfast. I eat from 12 to 8. If I’m super hungry before/after that time I eat. I have exercised during a fast and felt awesome. I have done 24hr fasts and felt awesome. When I get up in the morning I don’t have to worry about making breakfast so I can sleep longer/spend time on other things. I don’t think its the end all of dieting/weightloss but it is pretty awesome.
Also, in response to your assumption of what eating disorder I’m referring to, you’re wrong. Yes, anorexia is and eating disorder. So is bulimia, EDNOS (not otherwise specified- usually a catch-all for people who don’t meat the diagnostic criteria fully for AN or BN), and the binge eating and compulsive over-eating side of the spectrum. Or as I would like to call a continuum. If you are once anorexic, you are not immune to the other side of the spectrum. As I mentioned in my original comment, binging can be (and usually is) a direct result of restricting your intake.
So not only can fasting lead to anorexia, but it can also eventually leading one to binge-eat, become bulimic because of guilt associated with the binge, or become overweight/obese because of repeated overeating or binge eating to compensate for their heightened hunger.
“Try it for yourself before you go bashing it. There is very compelling evidence showing that the health benefits are nearly endless. This simple explanation of INTERMITTENT FASTING shows you this.”
Yeah, I did try it for myself. And at the time, I wanted to be healthy. I had no clue that I was mentally compromised, as are many people when they initially try something that’s only recommended for “healthy individuals”. And then I got obsessed. I got hooked on that “high” that you feel when you’ve gone for so long without food. It’s called starvation. I’ll spare you the rest of the story which involves much evolution with my eating and exercise habits, and just say that I wish I had never tried the whole fasting thing, as it lead to a going-on 7 year battle with an eating disorder.
Yes, this article warns that you should not attempt this if you already have an eating disorder. However, they also fail to point out that fasting or severely restricting your intake – no matter what your intentions (lose weight, health, stress relief, etc.) – can be enough to trigger someone into an unhealthy spiral into disordered eating or a full-blown eating disorder.
Jess, I know you bring some personal experience to this discussion, I’ve had my own struggles with eating, and I would consider the primary problem to be psychological – addiction, social/cultural influence, and marketing. I hope you have gotten over the 7 year battle, mine was about the same length.
As per the article though, I don’t see it hyping it with “drop 20lbs in 30 days” often done by other magazines.
Taking a step back and looking at the purpose of fasting and detoxing, here’s a quote from another EL article: “/article/detox-done-right/”
“If we look at fasting throughout history, we see that people have always fasted for the purpose of overall well-being and having insight into something deeper,” says Marc David, founder of the Institute for the Psychology of Eating in Boulder, Colo. “There are no historical references to fasting so as to look better in a bikini.”
I live in China now and they actually tell each other happily, “Oh, you’ve gotten fatter recently” and become worried when “you’ve become thinner”.
Did I ever even mention fasting in regards to losing weight? NO. You can get addicted to fasting (or dieting, or bingeing/purging, restricting and then overeating?bingeing, etc…) without looking good in a bikini as a motivator. Trust me. Eating disorders are not just a quick way to drop lbs (in fact, most people with eating disorders either maintain weight or gain!) They are mental disorders, that happen to manifest in a physical way as well.
Many see it as a way of maintaining control, because everything else feels out of control. Control what you eat/don’t eat, and nothing else will matter.
Some see their disorders as a way to cope.
“Don’t want to think about something that’s bothering you? Well, why don’t you just eat your whole kitchen and then throw up?”
“Tired of feeling your emotions? Why not eat them instead?!”
…You become consumed in it. It’s all that you can think about, and your life falls apart. Yes, you may lose weight. But then again, maybe not. But you’re still fooling yourself into thinking that you’ve got a handle on things when you really don’t. Not at all.