Having a good lie-in at the weekend might not make up for sleep loss during the working week, research suggests.
Scientists have previously found that a lack of sleep increases the risk of obesity and diabetes. However, it was not clear whether sleeping more on the weekend could balance the books and prevent such an uptick.
Now researchers say the signs are that it does not. Even if people have lie-ins at the weekend after a busy week, they found any benefits are transient, and that by the middle of another working week the body’s metabolism is just as disrupted, if not more so, than if they had not slept in.
Prof Kenneth Wright, co-author of the research from the University of Colorado Boulder, said: “It’s as bad if not worse in some cases.” While he said it is not clear if the practice could offer benefits if only used occasionally or with little sleep loss, the message is one of caution. “This yo-yo of going back and forth between burning the candle [at both ends] and catching up, and burning the candle and catching up, over the long term is probably going to do some harm,” he said.
Writing in the journal Current Biology, Wright and colleagues described how they studied 36 participants who spent 13 nights in the laboratory, the first three nights getting about eight hours sleep.
While eight people were allowed to continue with this pattern for the rest of the study, two groups of 14 people went on to have their sleep deprived, getting just under five hours a night. However, while one group was allowed to indulge in lie-ins and set their own bedtimes after four nights, those in the other group were not. After the weekend, both groups had a further two nights of sleep deprivation before being allowed to recover.
The results revealed those who were allowed to lie in did, with men sleeping more than women and participants not rising until about noon on the Saturday. But the team said that, even in that case, the total number of hours slept did not make up for the number of hours lost earlier in the week.
Moreover, by monitoring levels of the hormone melatonin, the team found participants’ internal body clocks were shifted to a greater extent when sleep deprivation was combined with lie-ins than if a sleep pattern was consistent.
All participants went from a restricted diet to eating whatever they wanted after the first three nights – with all showing a similar uptick in calories consumed.
While those who consistently had eight hours sleep a night showed no clear change in bodyweight at the end of the study, participants in the other two groups put on weight to similar degrees, gaining just under 1.5kg on average while they also developed a reduced sensitivity to insulin, a key hormone in regulating blood sugar levels. Further analysis suggested such effects could, at least in part, be down to participants in both groups snacking more after dinner on sleep-deprivation days, which the researchers say may disrupt metabolism in a number of ways.
Research has previously suggested that, while consistently failing to get enough sleep can increase the risk of an early death, a weekend lie-in might counter the effect. But Wright said it is not just mortality, but staying healthy that matters.
Others note that, while the latest study is small, it suggests lie-ins might not be enough to compensate for a working week of little slumber after all.
Dr Stuart Peirson, an expert in sleep and circadian clocks from the University of Oxford, who was not involved in the study, said: “You may live as long but this data, certainly in the short term, suggests there can be metabolic consequences.”
But Peirson noted that the study did not take into account cognitive prowess, which he said might have benefited from some catch-up snoozing among the sleep deprived.
