Can getting too little sleep make you fat? Or undermine your weight-loss efforts?
On the flip side, can adequate sleep help keep you svelte? It may sound farfetched, but a number of studies over the last several years have suggested such a connection.
Recently, a large study from Kaiser Permanente Center for Health Research, published in the International Journal of Obesity, found that dieters were most successful when they got just the right amount of sleep—six to eight hours a night.
Having lower stress levels helped, too. In another study, published in 2010 in the Annals of Internal Medicine, overweight people on calorie-restricted diets lost more body fat and retained more lean tissue (muscle) when they slept about eight hours versus five hours a night.
Other studies have linked decreased sleep to greater calorie intake and increased abdominal fat. One proposed mechanism is that not getting enough sleep affects appetite hormones, notably ghrelin and leptin, leading to increased hunger and food intake, decreased calorie burning and increased fat storage.
But the relationship between sleep and metabolism is complex, and not all research findings have been consistent. Reduced sleep may affect people differently.
More reasons to get your zzz’s
Studies have linked shorter sleep duration to increased risk of diabetes, colon cancer, strokes, heart attacks and early death. Sleeping too little (particularly five hours or less a night)—as well as too much (nine hours or more)—was found to be an independent risk factor for cardiovascular disease in a 2010 study in the journal Sleep.
Such associations do not prove cause and effect—shorter (and longer) sleep could be a marker for other conditions that increase the risk of health problems (such as depression, stress, pain or personal problems), though researchers try to control for these factors statistically.