Earlier bedtimes linked to weight loss in adults with prediabetes

Adults with prediabetes who go to sleep earlier may lose more weight, according to a new study from researchers at New York University's Rory Meyers College of Nursing. The trial, published in the journal Nursing Research, found that each hour earlier that participants fell asleep was associated with a loss of about 1.3 pounds over eight weeks. The researchers stressed that the finding shows an association only, not proof that an earlier bedtime causes weight loss.

The study enrolled 196 adults with prediabetes who were sleeping fewer than 6.5 hours a night. All participants took part in an eight-week lifestyle course covering diet, exercise and stress management. One group received only that course, while the other also received coaching aimed at gradually shifting their bedtimes earlier. The trial was led by Susan Kohl Malone, an assistant professor at the nursing college, and included researchers from the University of Delaware. It was funded by the National Institute of Nursing Research, part of the National Institutes of Health.

Both groups lost weight, but the sleep coaching did not produce a significant additional loss beyond what the lifestyle course achieved on its own. Neither group showed a significant improvement in blood sugar, a key measure in prediabetes. Still, the group that received sleep coaching fell asleep about 12 minutes earlier on average, and its members reported better sleep quality and less daytime drowsiness. Across both groups combined, earlier sleep onset tracked with greater weight loss.

The researchers offered several possible explanations for the link, including exposure to light late in the evening, the effects of stress hormones and hunger-regulating hormones, and the fact that late hours coincide with the time of day when the body is least sensitive to insulin. These mechanisms were proposed as hypotheses and were not directly tested in the trial.

The study has clear limits. It lasted only eight weeks, so it does not show whether the weight loss or the earlier bedtimes would be maintained over the long term. Sleep quality and daytime drowsiness were measured largely through self-reported logs, which can be less precise than objective measurements. The sample was also relatively small. The findings add to a growing body of research on the role of sleep in metabolic health, but they point to questions for larger and longer studies rather than offering a definitive recommendation.

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Caroline Mercer

World News Correspondent

Caroline Mercer covers public affairs, politics, business, culture and daily news for Core Memo. The role focuses on verification, context, and clear explanations for readers.

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