Simple bedtime change may help some individuals lose weight, study finds

Falling asleep earlier was linked to greater weight loss in adults with prediabetes, according to new research.

An analysis of data from a randomized trial led by the NYU Rory Meyers College of Nursing found that each hour earlier participants fell asleep was associated with roughly 1. 3 pounds of weight loss over eight weeks, although the finding 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," Susan Kohl Malone, an assistant professor at the nursing college and the study's lead author, said in a press release.

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The investigation, published in the journal Nursing Research, evaluated 196 adults diagnosed with prediabetes who routinely logged fewer than 6.5 hours of sleep nightly. Half the group took part in an eight-week lifestyle education course on diet, exercise and stress.

The other half received the same training alongside behavioral coaching meant to get them to go to bed earlier in gradual phases.

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Researchers tracked participants’ blood sugar, sleep and activity using sensors, sleep logs and wrist-worn monitors.

Neither group showed significant improvements in blood sugar. Both groups lost weight, but those receiving sleep coaching did not lose significantly more than those receiving lifestyle education alone.

"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," Malone said.

Participants who received sleep coaching did report better sleep quality and less daytime drowsiness, and they gradually began going to bed earlier.

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In a separate analysis across both groups, participants who shifted their sleep earlier tended to lose more weight.

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.

Remaining awake late also coincides with the hours when human 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.

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The trial ran for only eight weeks, which means it's unclear whether participants could maintain earlier bedtimes or sustain weight loss over the long term.

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While participants wore wrist monitors, key sleep metrics like rest quality and daytime drowsiness relied heavily on self-reported logs.

The findings also show an association across the study group rather than proven cause and effect.

Participants receiving sleep coaching fell asleep about 12 minutes earlier on average, according to Malone, which produced no measurable improvement in blood sugar levels.

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.