周末睡懒觉难以弥补一周来的睡眠不足
Weekend lie-in fails to make up for long hours in the week

翻译原文：

Workaholics are fooling themselves if they think a weekend lie-in can make up for lost sleep.

The first hard evidence has emerged that we are unable to catch up on lost sleep if it happens night after night - increasing the risk of obesity, heart disease and depression, while cutting mental dexterity.

While our bodies try to catch up on occasional loss by making us sleep more and/or more deeply the following night, this mechanism breaks down when there is chronic deprivation, say researchers at Northwestern University, Illinois.

 They report in the Proceedings of the National Academy of Sciences shows that when rats are partially sleep deprived over consecutive days they no longer attempt to catch up, despite an accumulating sleep deficit. "The ability to compensate for lost sleep is itself lost, which is damaging both physically and mentally," said Prof Fred Turek.

 Scientists estimate that in the 1960s people slept for more than eight hours. Now we are sleeping for about six. Symptoms of deprivation include weight gain, irritability, hallucinations and depression, said Prof Russell Foster, of Oxford University. It also impairs the ability of the brain to innovate.