Researchers at the Rory Meyers College of Nursing at New York University have reported an unexpected link between sleep and weight loss — one that has nothing to do with how many hours a person sleeps. According to Sky News Arabia, the team found that the clock time at which someone falls asleep may matter more than earlier studies had recognised.
The findings come from a trial of adults diagnosed with prediabetes, a condition in which blood sugar runs above normal but stays below the threshold for type 2 diabetes. People with prediabetes face a raised risk of developing type 2 diabetes, particularly if they are overweight or obese, have elevated glucose levels, high blood pressure or low levels of physical activity.
Why it matters
Suzanne Cole Malone, an assistant professor at the nursing school and the study's lead researcher, said sleep timing — not just sleep duration — appears to be an overlooked factor in weight loss and metabolic health, according to Sky News Arabia. The study suggests that public health advice focused only on getting enough sleep may be missing part of the picture.
How the trial was set up
The researchers recruited 196 people aged between 21 and 64 and assigned them at random to one of two groups. The first group followed an eight-week programme designed to improve lifestyle habits and served as the control. The second group followed the same programme but also received coaching sessions aimed at improving their sleep habits.
All participants were at high risk of type 2 diabetes and were in the habit of sleeping less than six and a half hours a night. Notably, the sleep coaching did not produce a meaningful change in blood sugar readings, even though participants reported feeling more alert and energetic during the day.
What the data showed
When the researchers analysed the results, a distinct pattern emerged among those who received the sleep guidance. Participants who began going to bed earlier showed a measurable shift in their blood sugar levels, regardless of how long they slept.
Malone suggested, according to Sky News Arabia, that falling asleep earlier may cut down on late-night eating and may bring mealtimes into closer alignment with the period when the body's metabolism works best.
The study, published in the journal Nursing Research, concluded that earlier sleep onset was associated with losing more weight over the eight weeks, and that this relationship held independently of total sleep duration. After statistical analysis, the team observed that the earlier a person went to bed and fell asleep, the more weight they lost on average. Each hour of earlier sleep onset was linked to a loss of about 1.3 pounds, or roughly 0.6 kilograms, across the eight weeks.
Possible explanations
The scientists offered several possible reasons for the connection. Beyond reducing opportunities for late-night snacking, an earlier bedtime may cut the time a person spends in front of electronic screens and limit exposure to artificial light at night.
Earlier sleep could also be tied to biological changes in the activity of the sympathetic nervous system, the part of the nervous system that governs the body's response to stress and pressure. It may also affect ghrelin, known as the hunger hormone, which plays a central role in regulating appetite and feelings of hunger. More broadly, going to bed earlier may reduce the environmental factors that trigger stress and disrupt the regulation of appetite and hunger.
Caveats and next steps
The researchers stress that the study is not definitive and carries several limitations. The trial was confined to people at risk of type 2 diabetes and ran for only eight weeks, which restricts how far the results can be generalised to the wider population. The relationship the team observed between sleep timing and weight loss also does not prove that earlier sleep is the direct cause of the lower weight.
Even so, the results open a new line of inquiry in research on sleep and health. Rather than concentrating solely on how many hours people sleep, the study points to the value of examining when they sleep, how that timing lines up with the body's biological clock, and what it means for metabolism and weight control. Watch for follow-up trials with longer durations and broader groups of participants to test whether the pattern holds.
