In common weight-loss advice, "get more sleep," should figure just as prominently as "eat less" and "move more," two researchers in Canada argue.
There is strong evidence that lack of sleep is contributing to the obesity epidemic, they said, and factors that contribute to obesity that have been given less attention than diet and exercise may at least partly explain why weight-loss efforts fail, according to the researchers.
"Among the behavioural factors that have been shown to impede weight loss, insufficient sleep is gaining attention and recognition," the researchers write in their editorial published today (Sept. 17) in the Canadian Medical Association Journal.
The researchers pointed to a 2010 study in which participants were randomly assigned to sleep either 5.5 hours or 8.5 hours every night for 14 days. They all cut their daily calorie intake by 680 calories, and slept in a lab. Participants who slept for 5.5 hours lost 55 percent less body fat, and 60 percent more of their lean body mass than those who slept for longer.
In other words, the sleep-deprived people held onto their fat tissue, and instead lost muscle.
In another study, published in July, researchers looked at 245 women in a six-month weight loss program and found that those who slept more than seven hours a night, and those who reported better quality sleep, were 33 percent more likely to succeed in their weight-loss efforts.
In a large analysis of the link, researchers looked at 36 studies, including 635,000 people around the world, and found that adults who didn't get enough sleep were 50 percent more likely to be obese, an children who didn't get enough sleep were 90 percent more likely to be obese, compared with those who got more sleep.
People's success in weight-loss programs varies greatly, and including advice about sleep in weight-loss programs could improve success rates, the researchers said.
While the exact way that losing sleep may contribute to obesity is not understood, studies have shown that lack of sleep affects the parts of the brain that control pleasure eating. It's also been shown that levels of the hormones leptin, ghrelin, cortisol and orexin — all of which are involved in appetite or eating — are affected by lack of sleep, the researchers said.
Health care providers might be better able to help their overweight and obese patients by screening for sleep disorders, according to researchers Jean-Philippe Chaput, of the Children’s Hospital of Eastern Ontario Research Institute, and Angelo Tremblay, of Laval University in Quebec.
Future research should look at ways that people could get more sleep — for example, by decreasing the amount of time they spend on other activities such as watching TV in the evening — and see whether getting more sleeps affects weight-loss efforts.
"Successful weight management is complicated, and a good understanding of the root causes of weight gain and barriers to weight management is essential to success," the researchers said.
While getting more sleep is not the solution for everyone who is struggling to lose weight, "an accumulating body of evidence suggests that sleeping habits should not be overlooked when prescribing a weight-reduction program to a patient with obesity."