What is time-restricted eating, and can it help you lose weight?

Time-restricted eating is basically a form of intermittent fasting, which has gained traction thanks to diet books such as The 5:2 Diet and The 8-Hour Diet.

Based on the theory that most of us spend way too many of our waking hours munching away, this diet method is as simple as shortening the number of hours during the day that you eat.

That could mean eating only between noon and 7 p.m. or 8 a.m. and 2 p.m. (it's up to you to decide how many hours you want to eat or fast per day). But the greatest benefits of time-restricted eating seem to occur when you stop eating earlier in the day.

For example, in one new study from the University of Alabama at Birmingham, when 11 overweight men and women spent four days eating only between 8 a.m. and 2 p.m. (a "restricted" schedule), and then four more days eating between 8 a.m. and 8 p.m., researchers found that time-restricted eating ramped up how much fat they burned at night. And, ironically, it led to fewer cravings throughout the day.

Granted, this was a small study, and the researchers note that more research will be needed to determine if time-restricted eating could lead to long-term weight loss. Still, previous animal studies suggest that TRE may effectively help lower body fat and cholesterol levels, and even improve insulin sensitivity. Plus, a 2017 review from the University of California, San Diego, shows that, in some cases, TRE can indeed lead to weight loss in both men and women.

Essentially, this style of eating revs your metabolism, says Eliza Whetzel-Savage, R.D., a registered dietitian with Middleburg Nutrition in New York City. When you cut the eating window down, you are creating a fasting period in which the body will have to use its own stored glycogen from carbohydrates and fat as fuel, she says. When the glucose and glycogen stores are used, the body switches over to a ketogenic state and burns fat for fuel.

Still, the diet has its challenges.

TRE In Real Life

If you haven't already guessed, time-restricted eating can be challenging, especially if you're a snacker or someone who doesn't like to eat much early in the morning, says Whetzel-Savage. You could easily wind up eating too few calories, developing nutritional imbalances, or building an unhealthy relationship with food.

The success of it really depends on the quality of the food choices in the eating period," she says. "If you're making poor nutritional decisions during that time, you probably won't see any weight loss, even if you fast. But, if the fasting period crowds out bad eating habits in the evening and your overall calorie intake goes down, then some people might see weight-loss results.

See what 1,200 calories looks like on 3 popular diets:

But even if dieters eat healthy, balanced meals during their "feasting" window, Whetzel-Savage explains that TRE could still be problematic for people who exercise frequently, and those with blood-sugar issues or diabetes. After all, if you go seven, eight, or more waking hours without eating, you could be putting yourself at risk of low blood-sugar levels. Heck, for some women, going even four hours without food is a recipe for hanger, fatigue, and dizziness.

However, proponents of time-restricted eating argue that the body quickly adjusts to a shortened "feast" window, and that it's actually what our bodies crave, at least from an evolutionary standpoint, says Traci Fields, and R.D. in New York City. Our ancestors didn't have constant access to food, so fasting was normal, and we already fast overnight naturally.

I use intermittent fasting all the time with my patients," says Fields. Typically, she recommends limiting food intake to seven hours throughout the day. During the fasting period, you can have as many calorie-free fluids as you want, like teas and coffee. If you need to crunch on something, celery is a great option that won't really impact the fast, and broth or a green vegetable juice can be helpful as a snack during the no-eating period before people adapt, she says.

Final Call

Realize that, even if you don't want to go hardcore with TRE, dialing back on excessive late-night noshing can be an easy way to cut down on eating that may have way more to do with cravings and stress than actual hunger, Whetzel-Savage says. And it can still help sync your eating patterns to your circadian rhythms.

For example, try to quit eating two to three hours before bed, she says. That will allow for at least a 12-hour fast every night and into the early morning. Meanwhile, when people have a hard time swallowing the whole TRE thing, Fields starts clients off with an overnight fast, starting at 7 p.m. and lasting until breakfast. "Then they can slowly extend the fast, she says.

In the end, TRE is only worth trying if it fits your lifestyle and helps you feel good. So if you want to give it a try, that's up to you and your doctor. But always listen to your body and if it needs food, feed it.