Everyone has heard that an adult needs to sleep 7–9 hours a day. Specialists named a night rest of such length a “beauty sleep”. And this is not just a figurative expression. The benefit of such sleep has been scientifically proven.

The Carolina Institute specialists say that it’s enough to sleep less than 7 hours two nights in a row to start looking less attractive. Researchers asked 25 students, girls, and young men, to sleep well for two nights in a row. The fulfillment of experimental conditions and the quality of sleep were recorded with special devices. Testees were then asked to reduce the amount of their sleep to 4 hours over the next two days. The photographs of participants without makeup were taken in both cases.