Too much/little sleep makes you fat

People who want to lose weight or prevent weight gain must exercise and eat well, but "we have to realise that sleep habits are also important," Dr Angelo Tremblay, of Laval University in Quebec City, who led the study, told Reuters Health.

While past studies have linked short sleep to weight gain, they have generally looked at a single point in time, making it impossible to determine whether lack of sleep actually causes people to put on pounds, Tremblay and colleagues note in their report.

To better understand the sleep duration-weight gain relationship, the researchers followed 276 men and women for 6 years. During that time, people who averaged 5 to 6 hours of shuteye a night gained 1.98 kg more than those who slept 7 to 8 hours, while those who slept for 9 to 10 hours gained 1.58 kg more than the average-length sleepers.

Increased risk of becoming obese
Short and long sleepers also showed greater gains in fat mass and waist circumference than average-length sleepers, and were significantly more likely to gain 5 kg or more. They also were at increased risk of becoming obese.

The most likely explanation for the findings, Tremblay noted in an interview, is that getting too much or too little sleep somehow disrupts appetite control by causing a reduction in leptin, a hormone that dampens appetite, while increasing secretions of the appetite-stimulating hormone ghrelin.

Tremblay noted that he and his colleagues recently found that short and long sleepers were also more prone to hypoglycemia, or low blood sugar, than average sleepers, which could increase appetite as well.

Other research has found an even stronger relationship between short sleep and weight gain in children, the researcher said, with sleeping less outweighing physical inactivity and extended TV viewing as a risk factor for obesity. However, he added, short sleep does not seem to confer an increased risk of weight gain among elderly people. – (Anne Harding/Reuters Health)

SOURCE: Sleep, April 1, 2008.

Read more:
Less sleep, bigger belly
Sleep tied to hunger hormone

April 2008