Researchers set out to test whether getting more sleep would improve blood sugar and spur weight loss in adults with prediabetes who sleep little. The answer turned on when participants fell asleep, not how long they slept: each hour earlier in bed was associated with roughly 1.3 pounds of weight loss over eight weeks, Fox News reported.
The randomized trial, led by the NYU Rory Meyers College of Nursing and published October 22 in the journal Nursing Research, followed 196 adults who logged fewer than 6.5 hours of sleep a night. Half took an eight-week lifestyle course on diet, exercise and stress; the other half received the same course plus behavioral coaching designed to move bedtime earlier in gradual phases.
Timing Beat Duration for Weight Loss
Both groups lost weight, but the sleep-coaching group did not lose significantly more than the lifestyle-only group. Across both groups, though, participants who shifted their sleep earlier lost more. A statistical projection found that each 60 minutes earlier of sleep onset was associated with about 1.3 pounds (0.6 kg) lost across the eight weeks. The finding is an association, not proof that an earlier bedtime causes weight loss.
Blood Sugar Did Not Significantly Improve
Neither group showed significant improvements in blood sugar, contrary to expectations. “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,” said Susan Kohl Malone, an assistant professor at NYU’s nursing college and the study’s lead author, in a press release. Newsweek reported that neither group extended sleep by a significant amount — about 10 minutes on average — and that the sleep-coaching group fell asleep about 12 minutes earlier on average.
Why Bedtime May Matter
Researchers pointed to the body’s internal clock. Staying up late increases exposure to artificial light, which can activate the body’s stress response and affect hormones that regulate hunger, NDTV reported. The hunger hormone ghrelin rises when people stay awake late, increasing the likelihood of late-night eating at the hours when insulin sensitivity is at its lowest. “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 contrast, falling asleep earlier may limit late-night eating and better align food intake with the body’s optimal metabolic window.”
A Broader Review Points the Same Direction — With a Caveat
A separate systematic review of 27 studies, reported by Vijesti, found that sleep interventions such as cognitive behavioral therapy for insomnia and sleep-hygiene programs were associated with an average BMI reduction of 0.64 kg/m² and with roughly 148 fewer kilocalories of daily intake. But five smaller studies of sleep extension alone, covering 138 participants, showed no statistically significant change in BMI — a signal that simply clocking more hours in bed is not a reliable weight-loss lever on its own.
Associations Between Sleep Timing and Weight Change
Does going to bed earlier cause weight loss? The study shows an association, not causation. Researchers tracked 196 adults for eight weeks and found that each hour earlier asleep was linked to about 1.3 pounds of weight loss, but the trial cannot prove bedtime caused the loss.
Did blood sugar improve? No. Neither the lifestyle-only group nor the group that received sleep coaching showed significant improvements in blood sugar, according to Fox News.
How much earlier did participants actually sleep? The sleep-coaching group fell asleep about 12 minutes earlier on average, and overall sleep duration rose by only about 10 minutes, Newsweek reported.
Who ran the study? The NYU Rory Meyers College of Nursing, with funding from the National Institute of Nursing Research at the National Institutes of Health.
The trial ran for only eight weeks, so researchers don’t know whether participants could maintain earlier bedtimes or sustain the weight loss over the long term. Malone said her team plans a follow-up study to look for an optimal bedtime threshold for people with prediabetes and to test whether an earlier bedtime produces greater weight loss in future trials.
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