Most of us who build up a “sleep debt” during the working week try to make up for it on the weekends by sleeping in.
But is that practice sufficient to undo the harmful metabolic changes that occur in our bodies when we persistently get too little sleep — changes that increase our risk of obesity and type 2 diabetes?
It may not be, according to a study published this week in the journal Current Biology. The study found that not only does sleeping in on the weekends fail to reduce those risks, it may actually increase them.
“Our findings suggest that the common behavior of burning the candle during the week and trying to make up for it on the weekend is not an effective health strategy,” said Kenneth Wright, the study’s senior author, in a released statement. Wright is director of the Sleep and Chronobiology Laboratory at the University of Colorado Boulder.
The study’s findings aren’t definitive — the number of participants in the study was too small. But the findings may be important if they are duplicated in other studies. That’s because many Americans are incredibly sleep deprived.
At least a third of American adults get less than the recommended seven hours of sleep per night, according to the Centers for Disease Control and Prevention.
For the current study, Wright and his colleagues brought 36 healthy young adults, aged 18 to 39, into their sleep lab for two weeks. Having the participants in the lab enabled the researchers to control and monitor their food intake, exposure to light and time spent sleeping.
Each participant was randomly assigned to one of three groups. For the first two nights, all three groups had similar sleep schedules: They went to bed around 11 p.m. and were permitted to sleep until 8 a.m.
After that, the groups were given different schedules. One — the “control” group — was permitted to sleep for up to nine hours per night for nine nights. Another — the “sleep restriction” group — was allowed to sleep for only five hours per night over the same period.
The third group — the “weekend recovery” one — was permitted to sleep for no more than five hours per night for five days. They then had two nights when they could sleep as long as they liked before returning to two more nights of restricted sleep.
Interestingly, on the nights when the people in the weekend recovery group could sleep as long as they liked, they tended to go to sleep and wake up later than they had at the beginning of the study. So, although they slept longer than on the sleep-restricted nights, that extra time ended up being only about 66 minutes, on average.
Men were able to make up more lost sleep than women.
The study found that the sleep-restriction group and the weekend recovery group gained weight during the study — an average of about three pounds over the 13 days of the study. That may not be so surprising, however, given that both groups also increased their after-dinner snacking on the days when their sleep was restricted — by an average of more than 500 calories each night.
The people in the control group, on the other hand, did not gain a statistically significant amount of weight during the course of the study.
The sleep-restriction and weekend recovery groups also experienced a decline in insulin sensitivity on the days when they received only five hours of sleep. This measure is important because a prolonged decrease in insulin sensitivity can make it difficult for the body to regulate blood sugar, which may in turn lead to diabetes.
Insulin sensitivity did improve among the participants in the weekend recovery group on the two days when they were able to catch up on their sleep. But then it worsened again once the “weekend” was over — to levels even lower than previously.
That finding surprised the researchers.
“It could be that the yo-yoing back and forth — changing the time we eat, changing our circadian clock and then going back to insufficient sleep is uniquely disruptive,” said Wright.
Not the last word
The study comes with several important caveats, most notably the study’s small size and relatively short duration. Also, the participants were all young, healthy adults. The findings might have been different in a more diverse group of people.
Still, the study seems to underscore what other research has been telling us for years: Not only is it important to get a good night’s sleep, it’s important to do so consistently.
For adults, that means getting at least seven hours of sleep on as many nights per week as you can.