Weight loss is tied to earlier bedtime, not the hours spent asleep

Whether it's four or eight hours, how much we sleep each night has become a focus for not just researchers but anyone looking to optimize their health. However, a new study suggests we might be focusing on the wrong side of the clock.In new research out of New York University's Rory Meyers College of Nursing, scientists found an unexpected link between sleep and weight loss – and it wasn't about the hours of shut-eye you clocked up. Instead, they found that when you fell asleep seemed to play a bigger role than evidence has so far recognized.“When we fall asleep – not just how much we sleep – seems to be an important and overlooked factor for weight loss and metabolic health,” says Susan Kohl Malone, assistant professor at the College of Nursing and lead author of the study.Now, it's worth pointing out that the trial conducted was on participants diagnosed with prediabetes. Essentially, people who have a high risk of developing type 2 diabetes – including those who are overweight or obese, have elevated blood glucose levels, have high blood pressure and are physically inactive. Basically, it's a lot of us – especially as we get older. In the study, Malone's team recruited 196 people aged between 21 and 64 years, who were randomly assigned either an eight-week lifestyle program (control) or this plan, as well as a sleep-coaching component. All participants were at high risk of developing type 2 diabetes and consistently slept less than 6.5 hours a night.Interestingly, the sleep coaching didn't change blood sugar readings, even if the participants reported feeling more alert during the day. But, from the data, the scientists found a pattern among those who were getting the sleep-coach guidance: Those who were going to bed earlier, regardless of hours slept, showed a meaningful change in their blood sugar levels.“Falling asleep earlier may limit late-night eating and better align food intake with the body’s optimal metabolic window,” adds Malone.As the scientist notes, it's more complicated than just an earlier bedtime. And many of us can't – be it work, family or even our own brain wiring – change our sleep schedule, even if we'd like to.So, caveats aside, the researchers found that across the 196 participants – so, both study groups – falling asleep earlier was linked to more weight loss over the eight weeks. And it was shown to be independent of the length of time spent asleep.Participants took part in video calls each week, discussing everything from healthy eating to physical activity in relation to preventing the onset of type 2 diabetes. Those who also received sleep coaching had sessions that detailed practical ways to "retrain" the brain to shift going to bed earlier and also falling asleep quicker when doing so.Everyone had to fill out daily sleep diaries and were fitted with glucose monitors and research-level wrist actigraphs to track sleep better than self-reporting can.Statistically, the scientists noted that the earlier someone went to bed and fell asleep, the more weight on average they lost. Each hour was associated with about 1.3 pounds (0.6 kg) lost over the eight weeks. The scientists suggest that besides late-night snacking, earlier bedtimes meant less screen time, exposure to artificial light, and biological shifts in the activity of the sympathetic nervous system and the hormone ghrelin.Essentially, it lowered the environmental triggers for stress and dysregulated hunger.“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,” says 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.”That said, across both cohorts, there wasn't a change in glucose levels, and data on daytime sleepiness was self-reported. But the findings did uncover improvements in sleep and weight reduction – with those receiving the extra coaching able to change bedtime habits over the eight weeks compared to those on the lifestyle plan alone.While this is by no means a conclusive study and has many limitations, it nonetheless offers an interesting new avenue when it comes to sleep research and health.The research was published in the journal Nursing Research.Source: NYU Rory Meyers College of Nursing