Could falling asleep earlier help with weight loss? Here’s what researchers found

Going to bed earlier sounds simple until you get under the covers and spend half an hour wide awake. In a study of adults with prediabetes, researchers paid attention to when people actually fell asleep. At the start, the average was about 12:50 a.m. Eight weeks later, most participants were still falling asleep after midnight. Even so, the people who moved their sleep earlier tended to lose more weight. Researchers at New York University and the University of Delaware reported the finding in Nursing Research. It gives them a reason to look more closely at the clock when they study weight loss.

What did the study find about sleep timing and weight loss?

An hour’s shift toward earlier sleep was associated with roughly 1.3 pounds more weight loss over the study, lead author Susan Kohl Malone told Newsweek. The number describes a pattern in the data. It doesn’t mean moving your bedtime from 1 a.m. to midnight will make you lose that much.

The change people actually made was much smaller. Participants who received sleep coaching fell asleep about 12 minutes earlier on average. The link with weight loss showed up across both study groups, including among people who didn’t receive the coaching.

How did researchers track sleep in adults with prediabetes?

The study enrolled 196 adults aged 21 to 64. All had prediabetes, meaning their blood sugar was higher than normal but below the threshold for type 2 diabetes. They also reported sleeping fewer than six hours a night.

Everyone took part in a lifestyle program that included guidance on eating and exercise. One group received additional help with sleep habits, including how to plan for an earlier bedtime. Wrist monitors tracked when participants fell asleep. Continuous glucose monitors recorded their blood sugar.

Participants slept about 10 minutes longer on average by the end of the study. Neither group had a statistically significant increase in sleep duration. About three-quarters of participants were still falling asleep after midnight.

Why might falling asleep earlier be linked to weight loss?

One possibility has less to do with sleep itself than with what happens in the hours before it. An earlier night might mean less time to snack while watching TV. Malone also pointed to the body’s internal clock. How the body handles glucose can vary over the course of the day.

The study didn’t test whether people lost more weight by eating fewer late-night snacks. People who fell asleep earlier may have changed other habits during the program, too. A follow-up study could help researchers see whether shifting sleep earlier makes a difference on its own.

Does bedtime matter more than how long you sleep?

The study can’t tell us. Marie-Pierre St-Onge, who directs Columbia University’s Center of Excellence for Sleep and Circadian Research, told Newsweek that sleep duration wasn’t included in the statistical models. Researchers couldn’t separate the effect of falling asleep earlier from the effect of sleeping longer. As St-Onge pointed out, moving bedtime earlier can itself be a way to get more sleep.

FAQs

Does getting into bed earlier count?

The study measured sleep onset, which is when participants actually fell asleep.

Would an earlier bedtime help anyone lose weight?

The study can’t answer that. It looked at adults with prediabetes who reported short sleep.