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In brief: One more reason to get enough sleep

In brief

One more reason to get enough sleep

Most of us are familiar with the short-term costs of sleep deprivation: reduced alertness, daytime sleepiness, irritability, and trouble concentrating. Long-term sleep loss can have more serious health effects, including depression, hypertension, health problems, and stroke. Now some research is suggesting that insufficient sleep also contributes to obesity. Although the mechanism isn’t entirely clear, the evidence implicates hormones that control appetite. If these findings are corroborated, getting enough sleep could emerge as a valuable addition to exercise and diet in achieving and maintaining a healthy weight.

Less sleep, higher body mass index

Several studies have examined the relationship between sleep and body weight. In one, researchers at Eastern Virginia Medical Center recruited 924 women and men, ages 18–91, from local medical practices and interviewed them about sleep habits, health problems, and sleep disorders. Weight and height measurements were taken and subjects were classified by body mass index, or BMI (see box below).

The higher a person’s BMI, the less sleep she or he got. The relationship was nearly linear, and it held even after excluding subjects with breathing problems, which are often caused by excess weight. Overweight and obese subjects slept, on average, 1.86 fewer hours per week — almost 25 minutes less per night — than normal-weight subjects. This sleep deficit correlated with a significant difference in their BMIs (Archives of Internal Medicine, Jan. 10, 2005).

The hormone connection

How might inadequate sleep affect body weight? Research conducted in sleep labs shows that sleep deprivation can alter metabolic functions such as the processing and storage of carbohydrates. It also influences the activity of several hormones, including leptin, which suppresses appetite.

Scientists at Stanford University and the University of Wisconsin hypothesized that ghrelin (GRAY-lin), an appetite-stimulating hormone, might be involved as well. To investigate, they examined data from a long-term study of sleep habits and disorders in 1,000 volunteers. The data, collected over 15 years, included surveys, overnight sleep studies, blood samples, and sleep diaries.

In people who slept less than eight hours per day, BMI rose in direct proportion to decreases in sleep time. Further, people who slept less had elevated ghrelin and reduced leptin, a combination that can result in hunger. These findings were published in the December 2004 edition of PloS (Public Library of Science) Medicine, an online peer-reviewed journal.

What now?

According to data from the National Sleep Foundation, most adults in the United States sleep about seven hours per night — one hour less than health experts recommend. Occasional sleep loss isn’t a problem, but a sustained sleep debt is likely to exact serious health effects. If getting enough sleep is a problem for you, discuss it with your clinician. You can also find good information on the Web site of the National Sleep Foundation, www.sleepfoundation.org.

There’s no proof that insufficient sleep contributes to obesity. Nor is it likely that it’s as important as diet, exercise, and genetics. But the relationship merits further investigation. If there is a connection, adequate sleep might be recognized as a factor in successful weight loss. In any case, many of us know from experience that lack of sleep tends to undermine our good intentions to eat well and exercise. More time awake also means more time to graze.

Last updated:	August 21, 2006