Science-- there's something for everyone

Thursday, March 21, 2013

To avoid weight gain, get enough sleep

Who hasn't suffered from inadequate sleep? Whether because of overscheduling or insomnia, we all face a bleary-eyed day from time to time. 

Insufficient sleep has a number of drawbacks, including irritability and inability to think or function. Interestingly, people who don’t get enough sleep often also succumb to weight gain. University of Colorado researchers led by Rachel Markwald investigated this link by limiting the sleep of some in-patient volunteers.

The scientists recruited sixteen healthy volunteers who all ordinarily get about eight hours sleep per night. The subjects gave up coffee and maintained a nine-hour per night sleep schedule for one week prior to the start of the study. Over the next five days, half the participants were only allowed to sleep five hours per night whereas the other half were given nine hours in which to sleep. The subjects were allowed to eat as much as they liked. After those five days, the two groups switched sleep patterns for another five days. Thus, everyone experienced a stretch of five days getting five hours sleep and another stretch getting nine hours sleep. Each person’s energy expenditure was monitored 24 hours/day.

People who only slept five hours/night used about 5% more energy than those allowed to sleep for nine hours. However, when given free reign, they consumed about 6% more calories, resulting in a net weight gain. After dinner snacking was the main source of additional calories during the five-hour sleep nights. This could have been due to changes in the circadian timing of meals, as evidenced by a delay in melatonin onset.

The order of the sleep conditions turned out to be significant. Subjects who slept nine hours first were already eating more than they needed (perhaps because of the novelty of being allowed unlimited food) and continued that practice after switching to five hours of sleep. In contrast, the people who started with five hours sleep gained weight during those five days but reduced their caloric intake after switching to nine hours of sleep per night. In particular, women gained weight during the five-hour regimens but lost it after switching to nine hours. Unfortunately, men overate during both phases. 

This suggests that if you do have to go through an interval of shortened sleep, you should follow it up by getting plenty of sleep for a few days. This study didn't address what would happen if you underslept for a prolonged period of time. It would be interesting to know whether you'd need an equal period of regular sleep hours to reverse any weight gain.

Getting enough sleep each night is probably not all you’ll have to do to shed a few pounds, but it might make things easier. Since adequate sleep is important for other reasons, it’s an easy recommendation to make.

Rachel R. Markwald, Edward L. Melanson, Mark R. Smith, Janine Higgins, Leigh Perreault, Robert H. Eckelb, & Kenneth P. Wright, Jr (2013). Impact of insufficient sleep on total daily energy expenditure, food intake, and weight gain Proceedings of the National Academy of Sciences of the United States of America : doi:10.1073/pnas.1216951110.

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