You already know that getting enough sleep matters. But here is something researchers just found that might surprise you: when you go to bed could affect how much weight you lose, especially if you have prediabetes.
Dr. Susan Kohl Malone and her team studied 196 adults between the ages of 21 and 64, all of them with prediabetes and all sleeping less than 6.5 hours a night. Everyone in the study went through an eight-week diabetes prevention program covering healthy eating, physical activity, and stress management.
One group also received sleep coaching. That coaching focused on sleep hygiene, better sleep habits, and gradually moving their bedtime earlier.
What the Study Found
Both groups lost weight and slept better by the end of the eight weeks. There was no significant difference in total weight loss or total sleep time between the two groups.
However, the sleep-coaching group did report better sleep quality and less daytime sleepiness. And one finding stood out in a bigger way.
The sleep-coaching group shifted their bedtime significantly earlier. Researchers then looked at whether the timing of sleep onset made a difference, and it did. Each hour earlier that participants fell asleep was linked to about 0.6 kilograms, or roughly 1.3 pounds, of additional weight loss over the eight weeks. That was true regardless of how long they slept.
To put that in plain terms: going to bed two hours earlier was associated with 2.6 more pounds lost compared to those who stayed up later.
One Thing That Did Not Change
The researchers had hoped that extending sleep would improve blood sugar levels. That did not happen. Neither group saw significant improvements in glucose, including the amount of time blood glucose stayed above 140 mg/dL.
As Dr. Malone explained:
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. However, our findings do raise the possibility that earlier sleep onset, independent of sleep duration, could be a promising target for improving metabolic health.
What This Means for You
If you have prediabetes and you tend to stay up late, this research suggests that shifting your bedtime earlier (even by an hour or two) could support your weight management efforts. The effect appeared to be tied to the timing of sleep itself, not just how many hours you get.
It is a small change that costs nothing. And for anyone managing prediabetes, even a modest difference on the scale can matter over time.
