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Night owls: If you are concerned about belly fat and the health risks it poses, chances are you’ll need to rethink your bedtime. A big international study of middle-aged and older adults suggests that sleeping late is related to obesity and a bigger belly. The study was published online on June 1, 2021. JAMA Network Open.It included about 137,000 people of various incomes from 26 countries. When participants answered questions on their sleep patterns, about 14 percent said they fell asleep at midnight or later. Compared to going to bed between 8 p.m. and 10 p.m., a later bedtime was related to a 20 percent higher risk of obesity (body mass index of 30 or more) or a big waistline (35 or more inches for girls, 40 or more for men). The risk was even higher (35% to 38%) amongst those that slept between 2 a.m. and 6 a.m. Long daytime naps were also related to an increased risk of belly fat, especially in women. Going to bed earlier (before 8pm) was not related to obesity. The study was observational and doesn’t prove that sleeping late will cause weight gain. But it’s plausible that it could: Researchers hypothesize that bedtime delays can throw off your circadian rhythm (sleep-wake cycle), which increases levels of the stress hormone cortisol and should play a task in belly fat.
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