Penn Study: Late Bedtimes = Larger Waistlines

Lots of studies have explored the relationship between sleep and weight, both in how sleep quantity impacts weight gain and how weight gain or loss impacts sleep quality. A new sleep study out of Penn’s Perelman School of Medicine, which claims to have included the largest cohort of healthy adults studied under lab conditions to date, found a connection between short sleep duration and weight gain.

A total of 225 study participants between the ages of 22 and 50 were selected at random be either sleep deprived or allowed to sleep normally; they spent up to 18 consecutive days in the lab. For five consecutive nights, those in the sleep-restriction group were allowed to sleep for only four hours a night, between 4 and 8 a.m. Not surprisingly, the sleep-deprived subjects ended up gaining more weight than the controls, who were allowed to sleep for 10 hours a night, from 10 p.m. to 8 a.m.

Researchers say the extra lbs came from the subjects consuming more meals—and therefore, more calories—than they would have had they had fewer awake hours, as well as the food choices they were making. In the late-night hours, subjects more often reached for foods that were higher in fat.

“In our study, we found that when adults restrict their sleep by delaying their bedtime and staying up late, they are at increased risk for weight gain because they consume a substantial amount of food and drink late at night which is higher in fat than food and drink consumed during morning, afternoon or evening,” said lead study author Andrea Spaeth in a press release. “This late-night eating contributes to weight gain by not only increasing overall daily intake but also by disrupting the timing of caloric intake.”

The study appears in the July issue of the journal Sleep.

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