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All You Need to Know About Intermittent Fasting

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You’ve probably heard the term intermittent fasting by now, seeing as everyone from tech entrepreneurs to your coworkers have cited it as a way to lose weight without cutting out entire food groups or counting calories. That sort of draconian restriction poses one of the biggest challenges to sticking with a diet, so eliminating it sounds almost genius. Plus, there’s some science to back it up: Research shows that intermittent fasting can improve metabolism and aid weight loss. But is it really the miracle that everyone thinks it is?

The concept of intermittent fasting is straightforward in that it entails not eating anything for a certain number of hours at a time, though there are different variations of it. There’s alternate-day fasting, in which you don’t consume calories one day and can eat an unrestricted amount the next. There’s modified fasting, more commonly known as the 5:2 diet, in which you eat 20 to 25 percent of what you normally would two days a week, and eat as usual the other five. And then there’s time-restricted feeding, which may be the most realistic for many looking to try it. With time-restricted feeding, you limit food intake to certain times of day that are more convenient for you, but still allow for 12 to 20 hours of fasting—so, for instance, only eating between the hours of 9 a.m. and 3 p.m.

Research shows that intermittent fasting can benefit certain people, and anyone who doesn’t like the idea of banishing foods from their diets may be a fan. (That might explain its popularity.) “A lot of diets out there, whether it’s keto or vegan, restrict what you eat rather than when you eat,” says Abbey Sharp, a registered dietitian and founder of Abbey’s Kitchen. “Studies show diets like intermittent fasting have a pretty high adherence rate versus those where you’re restricting different types of foods.” And because you have a smaller window to eat, it can obviously cut your caloric intake, which can lead to weight loss. Depending on your timing, you may not be able to go for dessert or a late-night snack.

It may also help regulate insulin production, Sharp says. One meta-analysis of current literature found that just about any intermittent fasting regimen can lead to weight loss, while alternate-day fasting was additionally linked to lower glucose and insulin levels. For health benefits, Sharp says, those who reap the most rewards are “people who are suffering from insulin sensitivity…the kind of people who are pre-diabetic and are at risk of high blood pressure and high cholesterol.”

Sharp doesn’t recommend intermittent fasting as a diet for weight loss purposes, especially since most research on it has only looked at the short-term implications. The strict timing of intermittent fasting can have bigger implications beyond yourself, too.

“Timing [your meals] can be hard for a lot of families; you might not be able to potentially eat with your family at night and the morning,” Sharp explains. “And if you have children and are trying to teach them how to have a healthy relationship with food, they’re going to be like ‘Why is mom not eating today? Why isn’t she eating with us?’”

On top of that, any kind of restriction—whether of calories, certain food groups, and the time window you can eat—can be taken too seriously. “Any time you set food rules up for yourself, it’s easy to fall down that rabbit hole and turning it into an obsession,” Sharp explains. And that obsession could lead to binge-eating in the window people have to eat, because they’re thinking about their next meal, she adds. That’s why intermittent fasting may be a slippery slope for anyone with a history of unhealthy eating patterns or disordered eating.

Of course, as with any major diet changes, you should talk to your doctor first to make sure it’s right for you. It may be popular, but whether it’s an option for your own life is a matter of your personal health and lifestyle.

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