Sleep more, lose more weight?

Recently lack of sleep has been linked to increased risk for obesity, although the reason for that link isn’t clear.  Is it a metabolic effect?  Do people just eat more because they’re awake more?  A new study asks: can more sleep help you lose weight?   The results are interesting.

The study went like this: 10 overweight adults were put on a modest low calorie diet.  Each person had 2 sleep lab sessions while on this diet: 2 weeks of 8-1/2 hours sleep per night and 2 weeks of 5-1/2 hours sleep per night.  Metabolism, body composition and weight loss were tracked for each subject.  Results: everyone lost about the same amount of weight for those two sessions, about 7 lbs average.  But, the type of weight lost was different. During the sleep deprivation period, fat loss was cut by more than half, while loss of lean body mass more than doubled.  In other words, in this study, sleep deprived people weren’t losing as much body fat.  Typically, when a person goes on a weight loss diet, they want to lose body fat.  Getting adequate sleep might help.

Why did more sleep make a difference in fat loss?  One study author noted that the subjects reported more hunger during the 2 week sleep deprivation period.  They had higher blood levels of the hunger-stimulating hormone ghrelin.  It makes sense; if you’re spending more hours awake, your body looks for more energy to stay alert and functional, and signals you to be hungry.  The hormone system that increases hunger could also depress fat-burning.  If you’re consuming a low calorie diet, your metabolism has to mobilize lean body mass to burn for energy.  This study was rather extreme, in that the subjects were very sleep deprived for 2 whole weeks.  Occasional lack of sleep is not likely to have as big an impact on your weight loss efforts.  But if you’re chronically sleep deprived, or you simply don’t sleep much, your low calorie diet might not be having the expected effect.

Does sleep deprivation make you gain weight?  This study did not examine that question.  If lack of sleep makes you hungrier, due to hormonal changes, and you eat too much, you could say lack of sleep causes weight gain by causing you to overeat.  There is evidence that the less people sleep, the higher the risk for obesity, especially in kids.  Whether this is due to less fat burning, more fat storage or more calories isn’t clear yet.

Will you lose more weight if you sleep more?  Not according to this study.  But the weight you do lose may be more fat, which is usually the goal of weight loss diets.  So do yourself a favor and get enough sleep.

Web MD has more information about sleep and diet.  National Geographic magazine has an excellent article about sleep in the May 2010 issue.

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