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Increasingly, studies show, getting the right amount of sleep is critical to maintaining a healthy weight. But does it matter when we sleep? A new study suggests that, yes, timing may be key: people who stay up late and sleep in tend to have worse diets, eat more at night and gain more weight, compared with those who go to bed at a reasonable hour.
Previous research in mice has demonstrated that messing with the animals' sleep and circadian rhythm — the body's internal clock, which is tied to the 24-hour day's light-dark cycle — causes them to eat at the wrong times and gain weight. The results were similar in the current study, led by researchers at Northwestern University Feinberg School of Medicine, who said it is the first to examine the relationship between the circadian rhythm, diet and weight in humans.
For one week, 51 people (23 late sleepers and 28 normal sleepers), aged 18 to 71, were asked to record what they ate in a food log — including time and types of food — and to wear a wrist actigraph that monitored their sleep and wake cycles.
On average, the late sleepers went to bed at 3:45 a.m., awoke by 10:45 a.m., ate breakfast at noon, lunch at 2:30 p.m., dinner at 8:15 p.m. and had their final meal at 10 p.m. Normal sleepers, by contrast, were asleep by 12:30 a.m., woke up around 8 a.m., had breakfast by 9 a.m., lunch at 1 p.m., dinner at 7 p.m. and their last snack around 8:30 p.m.
