believe it or not,
fasting wasn’t invented by Instagram hashtags — in fact, people have been fasting for thousands of years: Our ancestors did it (usually because they didn’t have a constant supply of food stashed in the fridge), and a number of religious events such as Ramadan revolve around some form of dietary fast.
As the name implies, intermittent fasting (IF) is a system during which you alternate between periods of restricted calorie intake and periods of normal eating. To be clear, IF does not restrict the kinds of foods you can eat — as do diets like Paleo or keto — just how much you can eat on certain days of the week. Many swear by IF because it’s easy to implement, requires nothing draconian like a horrible juice cleanse, and it has been proved to be one of the speediest and sustainable ways to torch fat stores and promote a lean physique.
RESEARCH SAYS …
Fasting has been a favorite research topic as of late, and a number of studies have found intermittent energy restriction — in which people ate fewer than 800 calories at least once per week — to be a valid weight-loss strategy, at least in the short term. In one study, weight loss was similar among participants following either a heart-healthy diet or a high-protein, reduced-calorie IF regimen for three months. However, the IF diet won out for minimizing weight regain after one year. Another investigation showed that IF was just as good at stripping body fat as simple calorie cutting. However, IF did a better job at preserving lean body mass.
As to how exactly IF helps sculpt your physique, theories abound: Some propose that IF flips a metabolic switch that encourages your body to burn more fat. Others state that since IF restricts your window of eating, you’re likely to eat fewer calories during the course of a week, helping trim the waistline with less risk of losing muscle. Even more studies propose that IF might help people get in touch with their true feelings of satiety and fullness on food-restricted days, which can put the brakes on overeating during times of normal food intake.
On another front, IF may have other positive effects on your body, such as reducing memory loss, improving cholesterol and blood pressure, and helping prevent diabetes by improving insulin sensitivity. And contrary to logic, IF could actually help — not hurt — your physical performance at the gym: A 2018 study in the
Journal of the International Society of Sports Nutrition found that athletes who participated in an every-other-day fasting protocol (eating 33 percent of their normal calorie intake on fasting days) for six weeks became more energy-efficient during exercise, reported less fatigue and experienced reduced bodyfat levels. Researchers theorize that occasional energy restriction might spur changes in hormones and mitochondrial function, helping you get more out of your workouts.