It's Not Just Sleep Duration: Bedtime May Also Affect Body Weight

The randomized controlled trial involved 196 people aged 21 to 64 who slept less than 6.5 hours per night. All participants took part in an eight-week diabetes prevention program focused on nutrition, physical activity, and stress management. Half of them also received sleep improvement counseling, which helped them gradually move their bedtimes earlier.

Both groups experienced improvements in sleep and reductions in body weight. However, participants who received additional counseling showed greater improvements in subjective sleep quality and daytime sleepiness.

When analyzing data from all participants, the researchers found an association between bedtime and weight loss. Each hour earlier that participants went to bed was associated with approximately 0.6 kg of weight loss over eight weeks. However, this was a statistical association: the study does not prove that going to bed earlier directly causes weight loss.

Despite improvements in sleep and reductions in body weight, blood glucose levels remained unchanged in both groups.

The researchers suggest that going to bed earlier may help with weight management by reducing late-night snacking and better aligning eating patterns with the body's circadian rhythms. Staying awake late may also be associated with changes in appetite-regulating hormones and metabolism.

The authors note that bedtime could become an additional target in diabetes prevention programs. However, further research is needed to confirm this hypothesis.