The Science of Intermittent Fasting

Many claims have been made about intermittent fasting. Some are overstated (about fat loss and anti-aging), but there are reason why it...

Sunday Special: The Pump app is more than customized, proven workouts. It’s a habit builder, an accountability system, and a way to interact with and learn from the best experts in health and fitness. Many in the Pump community say their favorite part of the membership is access to Q&As, videos, and in-depth articles that make it easier to eat better, train smarter, and live healthier.

This week, we discussed intermittent fasting in the app — and we’re sharing the discussion with the entire Pump Club village. If you want to see what The Pump app offers (it includes a risk-free 7-day trial), you can join here.


For five years, I practiced intermittent fasting…and then I stopped. But not for the reasons you might think.

My fasting started in 2010, and — at the time — few thought it was a good idea. Back then, the consensus was that breakfast was the most important meal of the day.

So what in the world was I doing waiting until 2 pm to have my first meal of the day?

I thought I was outsmarting human biology. All the things you hear today — how fasting boosts autophagy, anti-aging, metabolism, and protects your brain — were not mainstream. But there were hints in research — both anecdotally and in epidemiology — and a few smart scientists were sharing their belief in intermittent fasting to anyone who would listen. 

But as time went on, two things started to make me uneasy. 

First, the science wasn’t as conclusive as I once thought. I probably bought in, wanting to believe in all the benefits. Placebo and suggestion are an intoxicating combination. After all, one of the big revelations in my latest book is that our brains are wired to respond to novel ideas. The temptation of burning fat, building muscle, improving your sex life, and optimizing your hormones admittedly sounded a little too good to be true. And yet, the scientific foundations were there — albeit unproven. 

So I dove in and drank the Kool-Aid. But science is a game of patience. The latest study gets the headlines. However, results are reserved for those who don’t react to every piece of the puzzle and wait until there are enough pieces to see the big picture clearly. Once scientists started directly testing the theories, much of the early hype was overblown. Unfortunately, many of those findings now sit behind a reality that fasting advocates try to cover up.

Outside of the research (which we’ll discuss below), I had a deeper revelation: life isn’t meant to be dictated by health goals. It’s the opposite — your health plan should support your life goals. 

During the five years I fasted, I was healthy and fit by all measures, but some unhealthy habits were developing. I would watch the clock and wait to eat as if something magical happened at 2 pm. It could be 1:52, and I would be hungry, but I would wait 8 minutes. Some might call it discipline, but this was clearly a bad behavioral trait.

And then there was my hunger. Most of the time, I was not hungry. And then, other times, I would stubbornly fight my hunger.

Also, because of the fasting, I started rationalizing things that didn't make sense. At the time, I thought fasting was a fat loss advantage, so I could excuse behaviors that — in any other context — no one would think were healthy, such as gorging on meals that were beyond excessive. 

Despite all of that, I stuck with fasting. By 2015, I became a father. And I’ll never forget how I felt one morning after skipping another breakfast with my son. I openly wondered: will I go my whole life and never have breakfast together? 

It bothered me. And I wondered: How many memories will I miss because I believed I needed to fast to be healthy?

It was an “A-ha! Moment” on so many levels. Not only did I start to question if there were other ways I could replicate the alleged benefits of fasting (there are many — and most are more effective and proven than fasting), but I also started asking what I wanted my life to look like, and how my health could support that vision. 

So, I dropped fasting. Not because I thought it was bad (I’d still recommend it for some, as we’ll outline below), but because it was no longer for my lifestyle.

Today, I see fasting differently. A good tool for some, not for all, but a diet that thrives more on mysticism than results. If you’ve considered fasting — or are currently fasting — this isn’t designed to push you one way or another. It’s an honest look at what we know about fasting, who it can help, the different methods, and which claims are overstated. 

Fasting Isn’t A Miracle. It’s Just Another Tool

Walk into a mechanic’s workshop, and you won’t see just one device hanging on the wall. You’ll spot a peg board covered in tools of all different shapes and sizes. Each has a purpose and a value, but you wouldn’t necessarily use all of them simultaneously.

Diet strategies are not much different: You can use many tools to keep your body working and look how you want. Understanding those tools and when and how to best use them will help you keep your eating on track.

Intermittent fasting (IF) is incredibly popular and has many impressive claims. 

Read enough stories about intermittent fasting, and it starts to sound like magic, with benefits beyond weight loss. Proponents say—and some preliminary research agrees—that IF can help improve important health biomarkers (like fasting blood glucose and triglyceride levels), turn back the clock on time (anti-aging), and even help fight neurodegenerative diseases (health defense).

But I also have a unique perspective on the topic. I wrote a bestselling book on intermittent fasting in 2013. And I can confidently say I got A LOT of things wrong. 

However, it's important to note that these benefits are not one-size-fits-all. They vary from person to person and are influenced by the specific style of intermittent fasting you choose to adopt.

At the most basic level, intermittent fasting is something everyone does every day — it’s a break between meals. The most common occurs when you fast between your final meal of the day (usually dinner) and breakfast the following morning. (Hence the name, “break the fast.”)

Within the health and fitness realm, however, people use the term “intermittent fasting” to describe times when you intentionally extend that overnight fast for periods of time lasting anywhere from 12 to 24 hours.

The Lean Gains approach, for example, advocates a 16-hour fast. So if you started eating at 8 am, for instance, you would finish eating at 4 pm, fast for the rest of the day, and start eating again at 8 am the next day. The hours that you fast don’t matter; you go 16 consecutive hours without eating, followed by 8 hours where you do. That cycle repeats every day.

There’s also the Warrior Diet, a 20-hour fast and a 4-hour eating window. And the Eat Stop Eat protocol, which incorporates one full 24-hour break from eating at least one day per week. But then, for the rest of the week, you eat according to your desired schedule.

We’ll weigh the pros and cons of each of these approaches in a bit. For now, let’s address the even larger question at hand…

Does Intermittent Fasting Work?

For all the health benefits fasting recently linked to intermittent fasting, there’s one overarching reason why most people try it: To lose fat.

And if that’s your goal, then the answer is yes, intermittent fasting might help with fat loss — but not for the reasons you think.

The reason people following fasting protocols can lose weight is quite straightforward: They eat fewer calories than they burn throughout the day because the “eating windows” or weekly fast makes it harder to overeat.

Limiting the hours when you can eat helps you eat fewer calories overall. Think about it: let’s say your plan for weight loss requires you to eat 2,000 calories per day. It will be easier to stick to that goal if you can only eat for an 8-hour window in a day instead of 14 hours. When you consider fat loss alone (more to come on the other health, longevity, and disease-fighting benefits), intermittent fasting provides an easy-to-follow structure that naturally creates habits that make it harder to overeat.

Can you still over-eat within a limited time window and gain weight? Of course. But that’s the case with any eating approach. But instead of thinking about how many meals to eat, you just set a start time and stop time for your meals, and then eat in a way that feels best for you — assuming you stay within the amounts you should be eating.

The benefit is that this provides lots of flexibility and allows you to select the eating window (or style of IF — we’ll cover all of these to help you find the best option for you) that fits your lifestyle. Perhaps you skip breakfast, have your first meal around noon, and end early in the evening. Or you could push back later and then cater to your late-night eating preferences. 

Or maybe you do the opposite — start eating early and end in the early evening to avoid the late-night snack habit. Any of these approaches can work — it’s all about your preference.

All these intermittent fasting schedules can create an energy deficit that leads to weight and fat loss. (Again, we’ll cover a detailed breakdown of how to make this happen later in this post.) And while the details of nutrition still matter — proteins, carbs, and fats — it’s the simplified approach to eating less overall that makes intermittent fasting popular.

“Yes, the macronutrient splits matter a little bit. Yes, timing matters, maybe a bit more. But to the largest extent, all the data suggests the real contributor to fat loss and weight loss is total calories,” says Anthony D’Orazio, director of nutrition and physique at Complete Human Performance.

Many people will have you believe intermittent fasting is better for fast loss, but now dozens of studies have found that intermittent fasting (also known as time-restricted eating) is not superior for fat loss. However, it might be easier to get similar results with less thinking.

The most recent study tracked people for a year. One group counted calories, while the others didn’t track and limited their eating to 8 hours per day (from 12 pm to 8 pm). At the end of the study, the intermittent fasting group lost 10 pounds, and the calorie counters lost 12 pounds. As you can see, intermittent fasting was not superior. However, it offered a similar outcome with less thinking and calculation.

The reason is simple: when people restrict their calories to only 4 to 8 hours, research suggests they naturally reduce how much they eat by up to 500 calories per day. And many people find it easier to restrict when they eat instead of needing to track how much they eat. 

If you try time-restricted eating, don’t sweat the number of hours. Even in the current study, the first six months were spent eating 8 hours per day (to maximize sustainable weight loss), and the next six months eating 10 hours per day (to prioritize maintenance).

And when you consider that fewer hours during the day to eat means fewer calories (or having one day — like in the Eat Stop Eat method — where you don’t eat at all), you can see how week over week, it’s easy to limit your calories. After all, that’s what works with fat loss. Thinking less about any given meal or one day instead of seeing the big picture and trying to limit total calories weekly or monthly. When the deficit adds up over time, so does your weight loss.

OK, Does Intermittent Fasting Work Best For Anyone In Particular?

While the answer to that will differ from person to person, it’s worth noting that certain people tend to do better with fasting than others.

For example, research suggests that fasting works well for men. For example, this eight-week study of young males with experience with resistance training showed that those who ate only during an eight-hour window lost 16.4 percent of their fat mass, compared to just under 3 percent for a group who ate the same calories over a longer period.

Krista Scott-Dixon, the former director of curriculum at Precision Nutrition, cautions that those results may not translate to everyone since the study’s subjects “are naturally lean and already forget to eat half the time.”

On the other hand, there’s a mixed bag of results for women. While fasting can offer the same daily structure that helps restrict calories by having fewer hours to eat, the problem is that women tend to experience more unwanted side effects from fasting, especially with a prolonged fasting period (think 16 hours or longer) because of their hormonal environment.

“[Women’s] bodies are exquisitely sensitive to nutrient deprivation,” Scott-Dixon says. Women on a prolonged IF protocol may see a reduction in thyroid output, a decrease in estrogen, and other adverse hormonal effects. Pair that with an increase in exercise, and it could bring about menopausal-like effects (i.e. you stop getting your cycle) as well as powerful cravings.

Scott-Dixon also recommends that one group steer clear of IF: Anyone who has a history of, or tendency towards, disordered eating. “If you look at IF forums or groups, people are devoting an unhealthy amount of attention to when they get to eat, how much they get to eat, what they get to eat once they break their fast. It starts to get into a really behaviorally, emotionally weird area.” This behavior, Scott-Dixon warns, “can develop into a disordered eating kind of pattern.”

Does that mean that you need to steer clear of IF? Not exactly. It’s more of a general warning for any diet behavior. Counting macros and calories can lead to disordered eating just as much as intermittent fasting. So the point isn’t to avoid all potentially helpful dietary strategies, but — instead — consider how you feel and how much you stress while intermittent fasting. If you are stressing less and feel more in control, then great. If food and the clock start to dominate your life, you might want to question if it’s helping or hurting.

Ultimately, intermittent fasting success depends a lot on your personal preferences, schedule, and how you feel when you fast.  

If you find that intermittent fasting is a fit for you or something you want to try, you can do it and know it works as well as any diet that results in a calorie deficit. A study in the Journal of the American Medical Association Internal Medicine found that obese people who followed a more typical daily calorie restriction diet (they ate 75% of their target total every day) and those who followed an alternate-day fasting approach (they ate 25% of their target one day, then 125% the next) experienced similar mean weight loss totals over a year-long span. Again, it’s not magic. If you are compliant, it can deliver results — but not better than compliance on other plans. So the question is if a fasting window makes it easier for you to stick to the plan and make it sustainable.

Are There Other Health Benefits of Intermittent Fasting?

Intermittent fasting protocols reportedly slow down aging, improve mental acuity, increase longevity, reduce chronic disease risks, and decrease hunger. 

While many of those conclusions are based on preliminary research, science to date does back up some of them.

In a 2016 study, researchers concluded that intermittent fasting prevented neuron damage in the brain. Animal studies have found an association between fasting and reduced risk of lymphoma. Four studies have found a correlation between fasting and reduced symptoms of arthritis, and others have suggested that by reinforcing your circadian rhythms, fasting may promote longevity.

What’s fueling these benefits? Scientists will insist it’s a process called autophagy. In autophagy, your body kills old, diseased, or otherwise incomplete cells.

“A lot of neurodegenerative diseases are characterized by this build up of crud, [old cells that need to be cleared away,” Scott-Dixon says. “Autophagy is like the cleanup crew that kind of goes in and munches everything up.”

Autophagy is triggered by fasting. When you eat, autophagy hits snooze. Your body has to redirect the energy from the autophagy process to the digestive process to break down your food.

You wouldn’t feel this process at work. But when you fast, you might feel like you have greater mental clarity and better hunger control. Martin Berkhan, who designed the Lean Gains diet, says these effects are at least partially due to chemistry. Your body releases chemicals called catecholamines after 16-24 hours of fasting to keep you from feeling famished.

One of the catecholamines that get released during a fast is adrenaline, a stress hormone that improves mental cognition. “For some people, that feels amazing,” Scott-Dixon says. “[But] You’re not tuning into the universe in any magic way.”

When you read reports of people feeling more productive and focused when they fast, it’s not just your body’s chemicals at work. “There is also a mental component to it,” Berkhan says. “If you know you’re not eating until noon, you will find other things to occupy your mind with, such as work, which also helps keep your hunger in check.”

Transitioning from “I’m hungry” to “I’m thinking about something else” can take a few days. But Berkhan says that once you get used to it, the experience is liberating. He says he used to be preoccupied with food, following a bodybuilder’s regimen of constant feeding and macro-counting, but now he no longer “feels doomed to a life of obsessive calorie counting,” so he can concentrate more on his work.

That’s great, but there’s one big problem: There is no evidence that intermittent fasting increases autophagy more than cutting calories or other methods. Because autophagy is not exclusive to fasting. Exercise increases autophagy as well.

Put another way, the benefits of autophagy might not have anything to do with fasting itself; it just might be that when you fast and end up eating fewer calories, and that could be the primary benefit.

And that’s the big issue many researchers have with intermittent fasting claims. Because when you make calories equal in intermittent fasting and non-intermittent fasting groups, the results are identical. 

So if intermittent fasting helps you eat less, then great. If not, there might not be any direct, noticeable benefit from the fasting itself. 

And that doesn’t mention another fair question: do you always want more autophagy?

It’s rarely discussed, but autophagy also increases in diseases such as cancer and muscle-wasting disorders. That’s because when you’re in that state, your body breaks down protein. Sometimes this is good — and sometimes it’s bad. So, the end goal of just increasing autophagy can be a little misleading. 

And you could say that about many claims about intermittent fasting, including everything from brain health to cancer protection. 

Again, this doesn’t mean intermittent fasting is bad. It’s just that many of the claims — about anti-aging or overall health — are not substantiated. And, in many cases, there’s an alternative reason for the benefits (such as caloric restriction), or other (less sexy) options are more effective and have more science. 

Which Intermittent Fasting Schedule Should You Follow?

As we discussed earlier, there are lots of different fasting protocols. Despite some of the marketing copy you might see, none have been conclusively proven to be more effective than the others in a clinical study. So the question isn’t which one’s best, but which diet is best for you.

Finding a protocol that you’ll actually follow is more important than believing one fast period is superior to another. So if you know you can’t live without food for a whole day—or at least can’t do it and not rip your spouse’s head off—don’t do it.

Here are some options you can try.

12 hours off/12 hours on

The easiest fasting protocol is probably the least extreme: Fasting for 12 hours a day and eating during the other 12.

“If you tend not to eat that close to bed—say three hours before you sleep—all of a sudden, you’re at 11 hours without eating,” says D’Orazio. Wait an hour after you get up to eat breakfast, and you’re in the clear.

The drawback here is that, as far as calorie restriction goes, 12 hours can be a long eating window. In fact, even if you’re not following an intermittent fasting protocol, it’s possible that your daily meals only span a 13- or 14-hour window. Dropping your eating period by an hour or two may not be enough to put you at an energy deficit or change your habits in a way that will produce the fat loss goals you want.

If you opt for a 12/12 split, studies indicate that you may experience some health benefits of fasting, including increased insulin sensitivity. However, studies on Ramadan fasters suggest that increases in glucagon (an inducer of autophagy) happen more in the 16-hour range, so autophagy may not be maximized with a 12-hour fast.

The Lean Gains approach: 16 hours off/8 hours on

The approach is favorable because a 16-hour period is long enough to trigger autophagy (as discussed above), while an 8-hour eating window may be more conducive to fat loss for some. And you can eat around your training, placing emphasis on eating plenty of protein, controlling carbs, and scheduling meals around your workouts.

Ultimately, you’ll have to find the pattern that works best for you through trial and error, considering when you can actually work out. If your schedule is such that the only time you can lift is first thing in the morning, you may not have time to prepare a meal, eat, and digest all before your training.

The Warrior Diet: 20 hours off/4 hours on

In The Warrior Diet, author Ori Hofmekler took inspiration from history to design a 20-hour fast with a 4-hour feed—the idea is to mimic a hunter/gatherer lifestyle where you worked or battled all day, then chowed down at day’s end. Small snacks, like a piece of fruit or yogurt, are allowed during the day, but Hofmekler recommends eating most of your food in a giant, Viking-like feast at the end of the day. In this way, you’re not fully fasting on the Warrior Diet but underfeeding all day, then overfeeding at night.

Whether or not this is historically accurate or makes sense from an evolutionary standpoint is for anthropologists to debate. From a dietary perspective, one thing is clear: Limiting your eating to four hours a day might be difficult to overeat. Studies support this analysis. For example, a 2007 study found that having one meal per day was associated with greater weight loss and fat mass than eating three daily meals.

Note that we said “difficult” but not “impossible.” Roman soldiers and Vikings didn’t have high-calorie fare like Big Macs to chow down on. Fasting for even an extended period like this doesn’t give you a license to eat straight-up anything and expect to lose weight.

If you find that a 20-hour fast isn’t so much a path to mental clarity as it is the road to hangry town, this kind of protocol can be tough. You might have trouble concentrating at work, or worse, find you have a short fuse and lash out at people. In that case, a warrior approach is not recommended.

Also, if gaining muscle is your focus, based on what we know about muscle protein synthesis (a key role in gaining muscle), having protein at just one meal (or maybe 2) per day within a 4-hour window is not ideal for building muscle.

Eat, Stop, Eat: Take 24 hours off of eating once per week

Brad Pilon’s “Eat, Stop, Eat” protocol calls for a weekly fast of 24 hours. During that time you can drink non-caloric beverages (think: water, coffee, and tea—all without milk or sugar, of course), but otherwise, you take a break from eating.

For some, this single, extended fast can be less disruptive. Instead of thinking about when you will eat or not eat every day, you only have to consider it once a week. The approach is helpful from a weight loss perspective too—again, because of calories in-calories out.

The simple way to look at it is this: You know how, on any given day, you have a target number of calories to hit. The same is true for your total across the week. So, using the earlier example, let’s say your target is 2,000 calories per day. That would mean you’d have a 14,000-calorie allotment throughout the week. If you went one entire day without eating, you could spread the calories you saved across the other six days, meaning you could consume about 2,300 calories daily. Even though you’re eating more than you should be able to, because of the day where you eat 0 calories, this results in an overall energy deficit for the week and still lose weight.

There’s a way to structure this approach so that you can go for a 24-hour period without eating but not go an entire calendar day without eating a meal. Let’s say you finish your last meal on one day by 7 pm The following day, you’d skip breakfast and lunch, then eat a little later—after the clock strikes 7. Voila! You’ve just done a 24-hour fast but still eat on consecutive days.

You might think you’ll struggle with hunger during an extended fasting period. But gaining insight into this—what true hunger feels like—may help you distinguish between those times when you’re really hungry and those times when you may eat out of habit in response to something like boredom. This is why Scott-Dixon suggests trying a fast like this at least once to change your relationship with the feelings of appetite and hunger.

“You learn you can be hungry, and it’s OK, you’re not going to die,” Scott-Dixon says. “For people who are looking to lose fat, that can be very helpful.” Why? Because you’ll be better equipped to deal with those feelings on other days when you’re restricting calories or fasting for shorter periods.

The 5:2 Diet: Restrict yourself twice (and have more freedom)

The 5:2 Diet has become very popular over the last few years (It’s the diet that Jimmy Kimmel credits with helping him lose 25 pounds without exercise).

If going without food two days a week sounds daunting, fear not. This is not a full-on “fast” (i.e. go completely without food) as much as a twice-per-week extreme restriction. That means eating about 500 calories for women and 600 for men on “fasting days.”. (The founder of the diet, Dr. Michael Mosley, has more recently stated that going as high as 800 calories is ok.)

The good news? There aren't many restrictions on the other five days of the week because the two days of undereating create a big calorie deficit. Much like Eat Stop Eat, that allows you to eat a little more on the other five days than you “should,” meaning more flexibility. 

If you do the math on a 2,000-calorie per day diet, you can add up to 600 calories per day more than you would expect—or about a third of your total daily intake. You could eat an extra meal on those days, be fine, and still lose weight. (Remember, weight loss doesn’t happen in one day or meal. Undereating by so much for two meals per week simply enables loser calorie goals for the other five days.

Other than the two days per week at 800 calories or less, the fundamentals of his protocol are very similar to what you’d see in any healthy diet. The ten essential elements that Mosley lists in this article will sound very familiar to you: Eat protein and vegetables. Drink plenty of water. Be more physically active. Clean out the junk food from your house. Take it easy on the booze. But nothing is off-limits.

Basic fundamentals work—that’s why they’re the fundamentals. You could (and should) apply them to all of these approaches.

Some Helpful Intermittent Fasting Ground Rules and FAQs

Rule #1: Fasting is a tool. It’s not superior to other methods (based on what we know right now), but it can help.

Rule #2: If you try fasting, start slow. There’s a period of trial and error with any diet that requires adjustment and finding your comfort zone.

You should be asking yourself questions such as:

  • How do you feel?

  • Does fasting give you more or less energy?

  • Were you irritable or happy?

  • How does it affect your sleep?

  • How did it affect your workouts?

Consider all these factors to see if this kind of protocol will help you reach your goals.

You could start with a lower fasting period (like a 12:12) and work into longer durations. Gradually increasing your fasting time can help get used to some of the feelings of hunger you’ll experience. It will also help you notice and change the emotional attachment you might have to eat at certain times.

Berkhan suggests that as you’re getting accustomed to the feeling of fasting, drink coffee or other caffeinated beverages. “[It’s] quite beneficial for hunger suppression since caffeine works better on an empty stomach.”

Which brings up a good question: What can you consume without “breaking” the fast?

You don’t have to go hungry and thirsty during your fast period: Coffee’s fine, and so are other zero-calorie drinks like unsweetened tea.

How long should you follow a fasting plan?

Some people keep fasting plans indefinitely after discovering the one that works for them. 

Here’s where you could get into a bit of uncharted territory, scientifically speaking. There aren’t many longer-term studies on the effects of nonstop intermittent fasting. There have been some indications that prolonged fasting could have adverse side effects. For example, in the recent yearlong study that compared alternate-day fasting with calorie restriction, the fasting group saw increased LDL cholesterol.

Other research—and, according to Scott-Dixon, anecdotal evidence among coaching clients—indicated that long-term fasting can depress thyroid function and reduce testosterone. For example, in the eight-week study of resistance-trained males, the group following a 16:8 fast had a sharp decrease in overall body fat, and the same men also experienced a significant drop in testosterone.

When Scott-Dixon uses fasting with clients, it’s usually with overweight clients who are suffering the effects of metabolic syndrome, a series of risk factors that can lead to heart disease and premature death. Even with these clients, Scott-Dixon says she’ll only have them fast for about four weeks.

For most of her non-metabolic clients, her advice is to keep the “intermittent” in intermittent fasting. “I’d suggest no more than once every two weeks for most folks,” Scott-Dixon says.

While no research tells us the “best” amount of the health benefits of fasting, a bi-weekly fast is “enough to give you the health benefits of periodic fasting, but without most of the problems.”

Are there any times when you wouldn’t want to try intermittent fasting?

D’Orazio says he wouldn’t give a fasting protocol to an athlete who works out more than once per day. It’s a fairly common practice in his work, as some clients at Complete Human Performance are triathletes who lift in the morning and do endurance training in the afternoon or evening. To properly fuel for these workouts, D’Orazio says this sort of person shouldn’t follow an IF protocol.

The other time when you may want to steer clear of IF? Occasions when you are experiencing a lot of stress. Fasting, or even just energy reduction, is a stressor on the body, just like exercise, lack of sleep, or a intense job. When many stressors add up, one more may not be beneficial.

“I think one of the problems with any kind of diet or exercise intervention is that people consider it out of context,” Scott-Dixon says. “Even something that is “good” may not be good for YOU. We have to consider the whole picture. We can respond really well to intermittent, surprise stimuli, whether that’s an exercise challenge or a fast. What we don’t respond to as well are chronic stressors.”

Are there any times when intermittent fasting might be especially helpful?

We’ve mentioned that IF is a great way to help you “tune in” to your body and its hunger cues. Another use for intermittent fasting is during what’s politely called “hypercaloric eating”—basically, those times when you know you’re going to eat more than you should (think: you’re off visiting friends and know you’re going to have a huge meal followed by some bar-hopping later).

On this sort of day, restricting your eating window can be helpful. Just follow two guidelines: 

1) Make sure the first meal you eat when you break your fast is packed with protein and veggies (they promote satiety and will help prevent you from way overdoing it), and 

2) Use this technique only occasionally. It’s not meant to set up a lifestyle where you gorge yourself in the evenings. Having a big meal is not meant as a precursor to “punish” yourself with a fast. So if that’s your reasoning, then this approach is not best for you because it can lead to a bad relationship with food.

In the end, intermittent fasting is great for some but not for others. It works in some situations but is less ideal for others. Consider the different options, including your lifestyle and goals, which will help you figure out what’s right for you. 

Publisher: Arnold Schwarzenegger

Editors-in-chief: Adam Bornstein and Daniel Ketchell