Is calorie intake or time-restricted eating more important for weight loss? Here's what a new study says.

In a photo illustration, an alarm clock lies on its back between a crossed fork and butter knife.
Experts say the time at which you eat is, on its own, not as significant as some people believe it is. (Getty Creative)

Does when you eat really matter? Maybe not. According to new research from Johns Hopkins University, time-restricted eating may not actually be any more effective for weight loss than simply reducing your calorie intake overall.

Time-restricted eating is a trendy approach to weight management. It involves limiting the hours during the day when you consume food and sticking to a specific eating window, typically around eight to 12 hours. Along with weight loss, some people believe that this approach can help with overall health, including improvements in blood pressure, triglycerides and cholesterol. However, the research on its health benefits overall has yielded mixed results, with a recent study finding that people who practice intermittent fasting, a type of time-restricted eating, have a 91% higher risk of dying from cardiovascular disease.

Many people on social media say time-restricted eating is what helped them shed pounds. Proponents of the practice say one reason for this is because you are giving your body more time to burn fat for fuel, instead of burning the calories you get from food. However, the truth behind why it works as a weight loss tool for some people may actually come down to something a lot simpler: Time-restricted eating means you may simply consume fewer calories overall, putting you in a calorie deficit, which leads to weight loss.

What did the new study find?

The new study from Johns Hopkins University took 41 adults with obesity and prediabetes and randomly assigned them to either a time-restricted eating pattern with a 10-hour eating window or a regular eating pattern for 12 weeks. Both groups received prepared meals that were identical nutritionally and instructions on meal timing.

Dr. Nisa Maruthur, associate professor of medicine at Johns Hopkins Medicine and author of the study, tells Yahoo Life that the goal of the research was to “understand if restricting calories within a specific window of time earlier in the day would lead to more weight loss than eating later in the day with less restriction of timing — in the setting of stable caloric intake.” What researchers found was that after 12 weeks, both groups lost similar amounts of weight, and there were no significant differences in other metabolic health markers.

Though Maruthur notes that the study was small, researchers “did not find that time-restricted eating was beneficial for weight loss if calories are held constant.”

What a dietitian says

Julia Perlman, registered dietitian and co-founder of JAM Nutrition, tells Yahoo Life that “whether it’s through time-restricted eating or usual eating patterns, weight loss is achieved generally through expending more calories than you are consuming.” Exactly how much of a calorie deficit a person needs in order to lose weight is something that can be worked out with a dietitian.

Perlman notes that there are many things that “affect our weight loss success,” such as hormones, medications, metabolism, exercise and sleep. However, in general, the time at which you eat is, on its own, not as significant as some people believe it is.

“You can absolutely lose weight if you eat dinner at 9 p.m. — that’s something I’m always telling my clients,” she explains. “It’s more about what your full day of energy intake looks like.”

If it doesn’t really matter when you eat your meals, why do some people claim to lose weight by eating in a restricted window? Perlman says that it’s not about the time people are eating, but the fact that they are in a calorie deficit. The less time you allow yourself to eat, the less you may eat overall. If you close your kitchen at 6 p.m., you can’t have a late night snack that may push you out of a calorie deficit.

Perlman says that there can be significant drawbacks to time-restricted eating, which may vary from person to person. “For some people, it can lead to disordered eating or binge-eating behaviors,” she explains. “It may not sabotage your weight loss, but it can sabotage your relationship with food.”

She also notes that some people may throw nutrition by the wayside when they practice time-restricted eating — such as someone who fills up on fast food for their one meal of the day. “We also want to focus on health,” Perlman says. “If you’re eating through usual eating patterns, you’re giving yourself more time to eat and more time to get in more nutrition throughout the day.”