Simple sleep habit linked to weight loss

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Jasmine Laws

By Jasmine Laws

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The time adults with prediabetes go to bed could have a notable impact on their ability to lose weight, according to a recent study.

Researchers at New York University and the University of Delaware found that going to bed earlier was associated with greater weight loss among those with prediabetes—a condition where a patient has higher than normal blood glucose levels, but levels not high enough to be diagnosed as type 2 diabetes.

They concluded that the findings suggest that sleep timing—and not just sleep duration—could therefore be a promising lifestyle factor to use to assist weight management.

What The Study Found

Studies have previously shown that poor sleep—such as not getting enough sleep (i.e. less than seven hours) and going to bed late—is associated with weight gain and higher obesity risk. It is thought that this is because poor sleep can disrupt hormones in a way that promotes insulin resistance.

The researchers decided to explore this association further, and see how sleep factors could affect diabetes management. They included almost 200 participants in their study, between the ages of 21 and 64, who all reported sleeping fewer than six hours a night.

They found that sleep duration did not have an impact on blood glucose levels, but earlier sleep onset was associated with greater weight loss.

The 196 participants were split into two groups: one group that took part in an eight week lifestyle program without a sleep component, and one group on a lifestyle program with an added sleep component.

The participants spoke to researchers online in video calls every week, where they were told about healthy eating, exercise, and stress management—and for one of the groups, sleep sessions were included as well. The sleep sessions covered things like sleep hygiene and making plans to go to bed earlier to increase total sleep time.

On average, at the start of the study, the participants were falling asleep at around 12.50 a.m., and by the end of the study, three quarters of the participants were still falling asleep after midnight. In terms of sleep duration, neither group managed to prolong their sleep by a significant amount—the average was by about 10 minutes, so many still had less than six hours sleep a night by the end of the eight weeks.

They also were fitted with continuous glucose monitors to measure their glucose levels, as well as wrist monitors to track their sleep.

The results showed that regardless of the group participants were in, those who went to bed earlier experienced greater weight loss.

"What we found was a steady, linear relationship: the more someone moved their sleep onset earlier, regardless of which group they were in, the more weight they tended to lose," Susan Kohl Malone, the lead author of the study and assistant professor of nursing at New York University, told Newsweek.

"That worked out to about 0.3oz per minute, which translates to roughly 1.3lbs for a one-hour advance," she said. "The average shift we actually saw in the sleep group was about 12 minutes."

She said that her team is planning on doing a follow-up study to look for an optimal bedtime threshold for people with prediabetes, and also to test the hypothesis that an earlier bed time could result in greater weight loss in trials.

How Could An Earlier Bed Time Affect Weight Loss?

The researchers noted that there could be a number of reasons behind the association, such as that it curbs late night eating. Malone said that "falling asleep later means more time awake in the late evening," adding that people "tend to eat more in that window, are exposed to more artificial light, and are more drawn to high-calorie foods."

Although she said that the study wasn’t "designed to test mechanisms, so this is our working explanation, not something we showed directly."

She also said that "late evening is also when the body’s internal clock makes it least able to handle food: insulin sensitivity and glucose tolerance are at their lowest at night."

This could mean that "getting to sleep earlier may cut down on late-night eating and move food intake into a better metabolic window," she said, adding that "earlier sleepers also tend to have fewer obesity-related behaviors in general."

Marie-Pierre St-Onge, the director of the Center of Excellence for Sleep and Circadian Research at Columbia University, who was not involved in the study, told Newsweek that she agreed with the study authors' interpretation of why there could be a connection between an earlier bed time and greater weight loss.

"However, one cannot say that earlier sleep was associated with weight loss regardless of sleep duration because sleep duration was not included in the statistical models," she added.

She also said that the study "does not provide conclusive evidence that increasing sleep duration is not important or that advancing sleep onset is most important (or more important than sleep duration)."

"At this time, I would recommend following current guidelines to ensure adequate sleep duration and that advancing bedtime could be a good strategy to achieve this," she said.

Reference

Malone, S. K., Patterson, F., Hu, J., Goyal, C., & Melkus, G. D. (2026). Randomized Controlled Trial of Lifestyle Plus Sleep Extension Intervention on Adults With Prediabetes and Short Sleep. Nursing Research. https://doi.org/10.1097/NNR.0000000000000957

Contact Newsweek editors on this story: Kara Dolman and Paul Donnelley.

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What The Study Found

How Could An Earlier Bed Time Affect Weight Loss?

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