If the weekend is your time to catch up on sleep, you may want to rethink your strategy.
In young adults, using the weekend to make up for lost sleep during the workweek can lead to increased late-night munchies, weight gain and a lowered responsiveness to insulin, researchers report February 28 in Current Biology.
“The take-home message is basically that you can’t make up for abusing your sleeping clock by sleeping a few more hours on the weekend,” says Paul Shaw, a neuroscientist at Washington University in St. Louis who was not involved in the study. “It’s not as simple as saying, ‘Oh, if I sleep in on the weekends, I’ll be better.’”
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Since the 1990s, scientists have understood that missing sleep can affect a person’s metabolic health, causing behavioral and physiological changes that can lead to obesity and type 2 diabetes. Yet in 2014, roughly 35 percent of American adults reported sleeping fewer than the recommended seven hours per night, according to the latest data available from the U.S. Centers for Disease Control and Prevention.
Weekends may seem like an ideal time to catch up on sleep, but it was unclear whether that could actually work. So Christopher Depner, a sleep physiologist at the University of Colorado Boulder, and his colleagues put three groups of young adults in their mid-20s through different sleep regimens for roughly two weeks. One group slept about eight hours every night; another got roughly five hours a night; the third got around five hours on weeknights and slept whenever and as much as they wanted over a weekend.
Weekend recovery sleepers typically stayed up until midnight or 1 a.m. Friday and Saturday nights and slept until between 11 a.m. and noon. But they also stayed up late on Sunday, getting about six hours of sleep leading into the workweek. Cumulatively over the weekend, each got only about 1.1 hours more than their natural sleep cycles suggested they needed between Friday and Sunday nights, the researchers found.
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“So they did get extra sleep,” Depner says, but not enough to recover sleep lost during the workweek.
And, like the group that got too little sleep every night, the weekend sleepers gained something: weight. Lack of sleep disrupts appetite-controlling hormones such as leptin, Depner says. And shifts in the weekend sleepers’ natural biological clocks to later hours caused them to get hungry later. During the workweeks, both groups consumed roughly 400 to 650 Calories in late-night snacks, such as pretzels, yogurt and potato chips. By the end of the experiment, people in both groups had gained on average around 1.5 kilograms.
But when it came to insulin sensitivity, the two groups diverged. Sensitivity across all body tissues in the weekend recovery group dropped around 27 percent, compared with their baseline sensitivity measured at the start of the experiment. That was substantially worse than the 13 percent decline in those who consistently had little sleep. And the weekend sleepers were the only ones to have significant declines in liver and muscle cells — both important for food digestion — after a weekend of trying to catch up on sleep.
“That was very unexpected,” Depner says. Cycling between sleepless weeks and recovery weekends could “have some negative health consequences in and of itself.”
Peter Liu, a sleep endocrinologist at UCLA, questions whether these results are broadly applicable, especially in people who are chronically sleep deprived. He’s found that a few extra hours’ sleep was beneficial for insulin sensitivity in his studies of people who self-reported not getting enough sleep. “This is not the final word on this important topic,” he says.
But resting is “the third pillar of a healthy lifestyle: sleep, exercise and diet,” Liu says. “Just like you wouldn’t say to someone, ‘You need to be on a good diet from Monday to Friday, but on the weekend you can eat whatever you like,’ I think it’s the same principle here with sleep.”