Sleeping may actually help you to lose weight, and conversely getting less sleep might offset the effects of being on a diet to lose fat.
Researchers studied 10 overweight American men and women who lived in a sleep lab on two separate fortnights. During both periods, they were kept on the same calorie-restricted diet; but for one period, the participants slept for 8.5 hours per night, while during the other, they got only 5.5 hours of sleep.
It was found that the dieters lost the same amount of weight under both conditions - approximately 3 kg on average. But during the sleep-restricted period, they mainly lost muscle rather than fat. When participants got 8.5 hours of sleep, more than half of their weight loss came from shedding fat; when they got 5.5 of sleep, only one-quarter of their weight loss came from fat - translating to a 55 percent reduction in fat loss. Also, the weight loss during the sleep-restricted period came mainly from lean body tissue, like muscle.
Successful dieters always shed a certain amount of muscle but ideally one wants to limit that loss in favour of shedding excess body fat. Insufficient sleep, as the findings suggest, might interfere with that. The researchers found that under the sleep-restricted condition, participants reported greater hunger during the day compared with the 8-hour sleep condition - even though they consumed the same number of calories during both periods. They also had higher blood levels of acylated ghrelin, one form of the appetite-boosting hormone. This raises the question of whether, outside the tight control of the lab, the sleep-deprived dieters would have eaten more.
Although this was a small study, the findings add to evidence that sleep habits play a role in weight regulation. A number of studies have found that self-described ‘short sleepers’ - typically defined as those who get less than 6 hours of sleep each night - tend to weigh more or gain more weight over time than people who get seven to eight hours of sleep per night.
The study suggests that people trying to lose weight may want to ensure they are catching enough sleep at night, paying more attention to their daily diet, physical activity, as well as sleep. The researchers suggest that people decide for themselves how much sleep they generally need to feel refreshed the next morning; for some people that may be 6 hours, for others it may be 8. However, further studies with more subjects are needed in real-world settings on this subject.
