Are you eager to lose fat and gain muscle with less work?
You know that you need to eat fewer calories than you burn to lose fat. You also probably know that intermittent fasting can be an easy way to help you eat less.
However, you might be confused. Some people say intermittent fasting will make fat loss almost effortless. Others claim that intermittent fasting will make you lose muscle, and may even be dangerous.
If you read up on intermittent fasting, you can quickly learn that the major claims both for and against it are dubious at best, but in this article, I’d like to address a few myths that aren’t commonly addressed.
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Theoretically, you could lose fat by fasting around 12-24 hours, and then gain muscle when you do eat. Some people have also claimed that intermittent fasting “optimizes” or “balances” your hormones in a way that helps you store less fat and build more muscle.
The problem with this idea is that your total calorie intake evens out over the course of a day. If you burn 50 grams of body fat during a 16 hour fast, you’ll gain it back if you eat enough calories to maintain your body weight during the other 8 hours.
There’s also no evidence that intermittent fasting will change your insulin levels enough to affect your body composition.
In one study, people did lose fat after they switched to one meal per day instead of three meals per day. However, the differences were very small, and they weren’t exercising or closely monitoring their calorie intake. The study also used BIA to measure their body fat levels, which is notoriously inaccurate.
The bottom line is there’s no strong evidence that intermittent fasting will help you lose fat without also eating fewer calories than you burn.
This idea is similar to the first, yet takes the concept one step further. Like the first myth, there’s almost no evidence this is true.
A study commonly offered as proof that intermittent fasting does help you lose fat and build muscle simultaneously is a small review in 2011 that found that, on average, people who used alternate day fasting lost less muscle mass than those who cut calories every day.
The problem is the studies reviewed all used slightly different designs, which means the results could (and probably were), due to chance.
For a while, almost everyone recommended that you eat small meals throughout the day. Self-styled gurus everywhere claimed that it helped keep your blood sugar and hunger under control, boosted your metabolic rate, and provided more energy for your workouts.
Well, we now know that these ideas are false and the “guru pendulum” has swung in the other direction: many are now saying that eating many small meals throughout the day is actually bad for you, or at least not as good as eating fewer, larger meals.
There is some evidence that eating more than 3-4 meals per day doesn’t keep you as satisfied as limiting intake to a few meals per day. However, if that applies to you, you don’t need to be intermittent fasting to eat fewer, larger meals.
On the other hand, you can find studies wherein participants were less satiated on 3 meals per day, and found that increasing meal frequency increased feelings of fullness and made it easier to stick to their diets. And again, you can do this with or without following the intermittent fasting protocol.
You may have also heard that eating small meals will make it harder to lose fat because you’re keeping insulin levels higher throughout the day. Well, as you learned a moment ago, however, insulin levels average out over the course of the day, and worrying about small fluctuations is pointless. When you eat a large meal, your insulin levels will stay higher for longer, resulting in almost the same effect as snacking.
When we look at the research, the reasonable conclusion is if “grazing” throughout the day helps you stay lean and satisfied, then do it. There’s no evidence you’ll get better results with intermittent fasting.
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There is some evidence that women don’t respond as well to fasting as men.
One study found that alternate day fasting actually decreased women’s glucose tolerance, or how well they process sugar. Another study on women found that intermittent calorie restriction, which is similar to intermittent fasting, made them hungrier and less likely to continue dieting.
However, there’s little evidence that it’s dangerous, or worse for women than a normal meal schedule.
Other studies have shown that alternate day fasting or calorie restriction works extremely well for women. Even in the previous study where women felt hungrier and less happy with alternate day calorie restriction, they still lost slightly more weight than those who stuck to a daily calorie deficit.
If you’re a woman, there’s almost no scientific evidence that intermittent fasting is bad for you, or not as good as eating more often. That said, like with men, intermittent fasting doesn’t possess any particularly special properties for you, so you aren’t missing much if you don’t like it.
Most evidence shows that when you eat isn’t that important.
If intermittent fasting helps you eat less or gain more control over your diet, then do it. If you like to eat more frequently, that’s fine, too.
Having a plan that you can stick to, that allows you to hit your calorie and macronutrient goals, is what will give you the body you want. Don’t worry as much about when you eat.
Armistead Legge is the Editor-in-Chief for Muscle for Life and Legion Athletics. He has completed over 100 triathlons and cross-country, cycling, and adventure races, and has researched and written for over a dozen organizations, including the National Institutes of Health. When he isn't helping people get into the best shape of their lives, he's lifting weights, riding his bike, hiking, camping, reading, and making delicious food.