Going to bed an hour earlier may help with weight loss, study finds

Going to bed just one hour earlier may be linked to weight loss, according to new research. Researchers at New York University (NYU) found that adults with prediabetes who fell asleep an hour earlier lost an average of about 1.3 pounds over eight weeks, even though they did not sleep any longer overall.

The study was led by the NYU Rory Meyers College of Nursing and published in the journal Nursing Research. Its lead author is Susan Kohl Malone, an assistant professor at the college.

The trial enrolled 196 adults diagnosed with prediabetes who routinely slept fewer than 6.5 hours a night. Half of them took part in an eight-week lifestyle education course covering diet, exercise and stress.

The other half received the same training alongside behavioral coaching designed to get them to go to bed earlier in gradual phases. Researchers tracked the participants' blood sugar, sleep and activity using sensors, sleep logs and wrist-worn monitors.

The results showed no significant improvement in blood sugar in either group. Both groups lost weight, but those who received sleep coaching did not lose significantly more than those who received lifestyle education alone.

Participants who received sleep coaching did report better sleep quality and less daytime drowsiness. They also gradually began going to bed earlier, by about 12 minutes on average.

In a separate analysis across both groups, participants who shifted their sleep earlier tended to lose more weight. A statistical projection found that every 60 minutes earlier a participant fell asleep was associated with roughly 1.3 pounds of weight loss across eight weeks. The finding shows an association, however; it does not prove that moving bedtime earlier causes weight loss.

"When we fall asleep — not just how much we sleep — seems to be an important and overlooked factor for weight loss and metabolic health," Malone said in a press release.

The researchers suggested the body's internal clock may help explain the findings. Staying up late can increase exposure to artificial light, which may activate the body's stress response and affect hormones that regulate hunger.

Staying awake late also raises hunger hormones like ghrelin and increases the likelihood of late-night eating, at the hours when the body's insulin sensitivity is at its lowest. "In contrast, falling asleep earlier may limit late-night eating and better align food intake with the body's optimal metabolic window," Malone noted.

Malone added: "While we expected that extending sleep would improve glucose levels and weight loss in adults with prediabetes who sleep for shorter periods, this wasn't the case in our study."

The study has limits. The trial ran for only eight weeks, so it is unclear whether participants could maintain earlier bedtimes or sustain weight loss over the long term.

Although participants wore wrist monitors, key sleep measures such as rest quality and daytime drowsiness relied heavily on self-reported logs.

The study received funding from the National Institute of Nursing Research, a division of the National Institutes of Health, and was conducted in collaboration with researchers from the University of Delaware.