Adding sleep coaching to a diabetes prevention program did not improve blood sugar in a randomized trial of 196 adults with prediabetes who habitually slept less than six and a half hours a night. What did stand out was timing: across the whole trial, people whose sleep onset moved earlier lost more weight, while people who simply slept longer did not. The study was published in Nursing Research on October 22, 2026, by a team at NYU Rory Meyers College of Nursing with a coauthor at the University of Delaware.

How the trial worked

Participants were aged 21 to 64 and had prediabetes confirmed by an A1c test and short sleep confirmed by a wrist activity monitor rather than by their own estimate. Everyone took part in an eight-week lifestyle program delivered one-on-one over video, covering healthy eating, physical activity and stress management. Half were randomly assigned to also receive sleep sessions: sleep hygiene, stimulus control (training the brain to treat the bed as a cue for sleep) and a plan to move bedtime earlier in steps.

At the start of the program and again at the end, each participant spent two weeks at home wearing a continuous glucose monitor and a research-grade actigraph and kept a daily sleep diary. The main outcome was the share of time glucose ran above 140 mg/dL.

What it found

There was no meaningful difference between the groups on that glucose outcome, and neither program shifted glucose levels. Both groups slept more and lost weight, and the two groups did not differ significantly on either measure. The sleep-coached group did report clearly better sleep quality and less daytime sleepiness. Its sleep onset moved earlier within the group, but the gap between groups on timing did not reach statistical significance.

The finding getting attention came from an extra analysis the authors ran after the main comparison. Looking at all participants regardless of group, earlier sleep onset was linked to greater weight loss, and changes in total sleep duration were not. NYU's announcement of the results puts the size at about 1.3 pounds lost over the eight weeks for each hour earlier that people fell asleep.

What it does not show

The bedtime result is a post hoc association, which means it was not the question the trial was designed to answer and cannot show that going to bed earlier caused the weight loss. People who shift their bedtime earlier may also change when and how much they eat in the evening, and the authors point to late-night eating as one possible pathway. The trial lasted eight weeks, so it says nothing about whether earlier bedtimes or the weight change last. The authors themselves call sleep timing a promising target and say trials built specifically to test it are needed. The work was funded by the National Institute of Nursing Research.

Where it fits

The American Academy of Sleep Medicine and the Sleep Research Society recommend that adults sleep seven or more hours a night on a regular basis, and the CDC lists consistent sleep and wake times among its basic sleep habits. This trial adds a narrower question to that picture: not only how long people sleep, but when. For someone with prediabetes, the most useful takeaway is that standard lifestyle programs still worked on weight in both arms, and bedtime is a reasonable thing to raise at the next visit with a clinician or diabetes prevention coach.

This article reports research and expert guidance. It is not medical advice. Talk to your clinician before changing medication, treatment or a medical diet.

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