Earlier bedtime linked to weight loss in prediabetes, suggests study

Going to bed earlier is associated with weight loss in people with prediabetes, according to a randomized controlled trial led by researchers at NYU Rory Meyers College of Nursing.

The study, published in the journal Nursing Research, found that adding sleep coaching to a diabetes prevention lifestyle program helped participants sleep better and feel less sleepy during the day, but did not change blood sugar levels. The results also point to sleep timing as a promising new target for 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,” said Susan Kohl Malone, assistant professor at NYU Rory Meyers College of Nursing and lead author of the study.

Studies show that poor sleep—for instance, getting less than seven hours of sleep, going to bed late, or irregular sleep patterns—is connected to weight gain and poor blood sugar (glucose) control. Sleeping too little can raise levels of stress hormones such as cortisol, which promote insulin resistance and can shift appetite hormones in ways that increase hunger and food intake. Similarly, going to sleep late can lead to late-night eating, when insulin sensitivity and glucose tolerance are at their lowest point.

“In contrast, falling asleep earlier may limit late-night eating and better align food intake with the body’s optimal metabolic window,” said Malone.

To better understand the role of sleep health in diabetes prevention, Malone and her colleagues designed a randomized controlled trial for adults with prediabetes who sleep less than 6.5 hours a night. The 196 participants, ages 21 to 64, were randomly assigned to take part in either an eight-week lifestyle program or the lifestyle program with an added sleep component.

Participants met with researchers weekly in video calls to learn about healthy eating, physical activity, and stress management for diabetes prevention. Those in the lifestyle-plus-sleep group received sleep-focused sessions, including sleep hygiene, retraining the brain to see the bed as a cue for sleep, and a plan to incrementally shift their bedtime earlier to increase their total sleep time. All participants completed daily sleep diaries. Before and after the program, they wore both continuous glucose monitors to measure glucose levels and research-grade wrist monitors (actigraphs) to track sleep.

Neither program changed glucose levels. Both groups saw improvements in sleep and weight loss. The lifestyle-plus-sleep group had greater improvements in self-reported sleep quality and daytime sleepiness compared to the lifestyle group, and its participants’ sleep timing shifted significantly earlier.

When the researchers looked across all participants, regardless of group, falling asleep earlier was associated with greater weight loss independent of sleep duration. Each hour earlier that participants fell asleep was associated with about 1.3 pounds of weight loss over the eight weeks.

In addition to curbing late-night eating, the researchers point to several mechanisms that may explain why falling asleep earlier could help with weight loss. Staying up late is linked to more exposure to artificial light, increased activity in the sympathetic nervous system (which controls the body’s “fight or flight” response), and increased appetite driven by the "hunger hormone" ghrelin.

“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 Malone. “However, our findings do raise the possibility that earlier sleep onset, independent of sleep duration, could be a promising target for improving metabolic health.”

Reference: Malone, S. K., Patterson, F., Hu, J., Goyal, C., & Melkus, G. D. (2026). Randomized Controlled Trial of Lifestyle Plus Sleep Extension Intervention on Adults With Prediabetes and Short SleepNursing Research https://doi.org/10.1097/NNR.0000000000000957