In fact, grabbing those extra zzz's could actually be harmful.
After racing through the work week with too few hours of sleep, nothing feels quite so luxurious as sleeping in on a Saturday morning. But a new study, just published last week in the journal Current Biology, has found that weekend lie-ins could actually do more harm than good.
Any benefits gained by the extra sleep are transient and, by the middle of the following sleep-deprived work week, the body's metabolism is "just as disrupted, if not more so, than if they had not slept in" (the Guardian). In the words of study co-author Kenneth Wright of the University of Colorado, Boulder, "It’s as bad if not worse in some cases."To reach this conclusion, researchers divided 36 study participants into three groups. All got 8 hours of sleep for the first three nights in a laboratory. Then, one group slept 9 hours per night for an additional 9 nights. Another group slept 5 hours per night for the same amount of time. A third group slept 5 hours for 5 days, followed by a 2-day weekend during which they could sleep in as much as they liked, before returning to two more days of reduced sleep.
Researchers determined that weekend lie-ins did not add up to the number of sleep hours lost during the week. By monitoring levels of hormone melatonin, participants' internal clocks were shifted more by sleeping in than if their sleep-deficient states were maintained.
Furthermore, those participants whose sleep was restricted gained just under 1.5 kg (3.3 lb) on average and developed a reduced sensitivity to insulin, likely due to increased snacking after dinner on sleep-deprivation days, which can disrupt metabolism. Co-author Christopher Depner stated in a press release:
"Our findings show that muscle- and liver-specific insulin sensitivity were worse in subjects who had weekend recovery sleep. This finding was not anticipated and further shows that weekend recovery sleep is not likely [to be] an effective sleep-loss countermeasure regarding metabolic health when sleep loss is chronic."
There you have it. There's really no way to recover a sleep deficit. All you can do it go forward and make a better effort to squeeze in more zzz's on a regular basis. Combine this research with that of Matthew Walker, author of Why We Sleep, and you'll be hard-pressed to justify that late-night Netflix habit:
"Once you know that after just one night of only four or five hours’ sleep, your natural killer cells – the ones that attack the cancer cells that appear in your body every day – drop by 70 percent, or that a lack of sleep is linked to cancer of the bowel, prostate and breast, or even just that the World Health Organization has classed any form of night-time shift work as a probable carcinogen, how could you do anything else?"