Many people sleep too little on weekdays – and then catch up on sleep on weekends. But to what extent does this strategy help against the health consequences of lack of sleep? As researchers in a sleep study found, the change in rhythm apparently messes up the body clock. As a result, insulin resistance and the tendency to become overweight increase even more than in people who constantly sleep too little. This means: If you want to do something for your health, you have to sleep regularly enough – catching up on the weekend is of no use.
Sleep is essential for human survival. Because during this time, many processes run in us that are crucial for the regeneration of body and mind: growth hormones repair cell damage and promote wound healing, the immune system uses this break to intensify the fight against pathogens. Our brain also needs sleep in order to flush out waste materials, to store what has been learned and to prepare the synapses for the absorption of new information. It is correspondingly unhealthy if we sleep too little. Studies have shown that this affects not only concentration and mental performance, but also metabolism and the cardiovascular system. Frequent lack of sleep can thereby promote obesity, diabetes and heart problems. This is one of the reasons why the World Health Organization recommends at least seven hours of sleep a day.
Two weeks in the sleep laboratory
The problem: Most people barely get enough sleep in everyday life. Getting up early for school or work and the desire to spend at least a little time with family, hobbies or joy after work leads to a lack of sleep for many. Most of the time, you can only make up for the lack of sleep by sleeping in late at the weekend. But can this weekend sleep compensate for the harmful effects of a lack of sleep on weekdays? Christopher Depner from the University of Colorado at Boulder and his colleagues have investigated this.
For their study, the researchers asked 36 young, healthy subjects to spend two weeks in the sleep laboratory. For the first three days, everyone followed a control rhythm with around nine hours of sleep a night. Then the scientists divided their subjects into three groups: the control group continued to sleep for nine hours, a second group got only five hours of sleep every night. The third group, however, followed a typical weekly rhythm: they got only five hours of sleep for five days, then they were allowed to sleep for two days as long as they wanted. This was followed by another three days with limited sleep. In all subjects, the researchers checked body weight, calorie intake and the amount of food, as well as the insulin sensitivity of various tissues and the level of the sleep hormone melatonin.
Weekend sleep is rather negative
It turned out that the lack of sleep led to measurable consequences for all subjects in the five-hour regime. On average, both the long-term sleepers and the weekday sleepers increased 1.3 to 1.4 kilograms in the course of the experiment – mainly because they had had more snacks in the evening and at night, the researchers report. Due to the lack of sleep, the rhythm of the internal clock also shifted back, as the melatonin values showed. The sugar metabolism also reacted: In the group of long-term sleepers, the insulin sensitivity of the test subjects fell by an average of 13 percent. The surprising thing, however, is that even the inserted weekend with a long sleep in did not compensate for these negative effects. The subjects in this group slept a good hour longer on Saturdays and Sundays and temporarily some blood values also improved. But this effect didn’t last beyond the weekend.
As soon as the subjects returned to workday mode, their values became even worse than those of the continuous short sleep group, as the researchers report. The insulin sensitivity among weekend sleepers even decreased by up to 27 percent instead of just 13. “The insulin sensitivity of muscles and liver was therefore significantly worse for weekend sleepers,” reports Depner. “We didn’t expect that – and it shows that sleeping in at the weekend is apparently not an effective countermeasure against the effects of chronic sleep deprivation.” The researchers suspect that these surprisingly negative consequences are due to changes in the normal rhythm. “It’s like a yo-yo effect: on weekends we change our meal times and our internal clock and then return to the old rhythm of lack of sleep on Mondays – that’s extremely disruptive,” explains co-author Kenneth Wright from the University of Colorado.
In other words, if you want to do something good for your body, you should try to get at least seven hours of sleep regularly. “Because the common behavior of saving on sleep on weekdays and then catching up on everything at the weekend is not an effective health strategy,” says Wright.
Source: Christopher Depner (University of Colorado, Boulder) et al., Current Biology, doi: 10.1016 / j.cub.2019.01.069