Prediabetes: Earlier bedtimes linked to weight loss
Researchers found that each hour of earlier sleep corresponded to 1.3 pounds of weight loss over eight weeks, though the study did not prove causation.
By Elena Perry ·
Adults with prediabetes who went to bed earlier lost more weight than those who did not, according to a new study published in the journal Nursing Research. An analysis of data from a randomized trial led by the NYU Rory Meyers College of Nursing found that for every hour participants went to sleep earlier, they lost approximately 1.3 pounds over an eight-week period. The researchers emphasized that the finding represents an association rather than a direct cause and effect relationship.
The study evaluated 196 adults diagnosed with prediabetes who reported sleeping fewer than 6.5 hours per night. Half of the participants completed an eight-week lifestyle education course covering diet, exercise, and stress management. The other half received the same training along with behavioral coaching designed to encourage them to go to bed earlier in gradual steps. Researchers monitored the group using sensors, sleep logs, and wrist-worn devices to track blood sugar, sleep patterns, and physical activity.
Neither group demonstrated substantial improvements in blood sugar levels. While both groups lost weight, the cohort receiving sleep coaching did not lose significantly more weight than the group receiving only lifestyle education. Susan Kohl Malone, an assistant professor at the nursing college and the study's lead author, stated that the team had expected extending sleep would improve glucose levels and weight loss, but the data did not support that outcome.
Participants in the sleep coaching group reported higher quality sleep and reduced daytime drowsiness. They also gradually shifted their bedtimes to earlier hours. In a separate analysis across both groups, those who moved their sleep schedule earlier tended to experience greater weight loss. Malone noted that the body's internal clock may explain these results. Staying up late increases exposure to artificial light, which can activate stress responses and alter hunger hormones. Late-night wakefulness also coincides with periods when human insulin sensitivity is at its lowest.
Malone suggested that falling asleep earlier may limit late-night eating and better align food intake with the body's optimal metabolic window. The trial lasted only eight weeks, leaving the long-term sustainability of earlier bedtimes and weight loss unclear. Key sleep metrics, such as rest quality, relied heavily on self-reported logs despite the use of wrist monitors.
Participants receiving sleep coaching fell asleep about 12 minutes earlier on average, according to Malone. This small shift 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. It was conducted in collaboration with researchers from the University of Delaware.
