Sleep off the fat

A study of more than 68 000 women found that those who sleep less than five hours a night gain more weight over time than those who sleep seven hours a night. So says Sanjay Patel from Case Western Reserve University, Cleveland, Ohio. Patel found that women who sleep for five hours a night or less gained an average of 0.7 kilograms more over 10 years than those who slept seven hours or more. The short-sleeping group was also 32% more likely to have gained 15 kilograms or more and 15% more likely to have become obese.

Interestingly, the short-sleepers actually ate fewer calories than the longer sleepers, overturning the common idea that over-eating among those who sleep less explains the weight differences. Patel suggests that a lower metabolic rate or less fidgeting resulting from less sleep may be the reason behind the weight gain.