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Say goodnight to obesity?
Say goodnight to obesity?
Studies suggest that getting enough sleep can curb appetite and lead to a slimmer you.
Sally Squires the Washington Post
August 1, 2006
If sleeping to lose weight sounds like a dream, then go back to bed. The power of sleep in regulating appetite, body weight and risk of type 2 diabetes in adults and children is strong enough that some scientists wonder if it may soon be the newest tool in the battle against obesity.
"Can a good night's sleep make us slimmer?" asks Danish nutrition researcher Arne Astrup in an editorial in this month's International Journal of Obesity. Maybe, concludes Astrup, citing a growing body of research that points to sleep as a key player in hunger and appetite control.
The latest evidence comes from a study of 422 Canadian children, ages 5 to 10 years. Researchers at Quebec's Laval University found that youngsters who slept eight to 10 hours per night had 3.5 times the risk of being overweight compared with a similar group of children who slept 12 to 13 hours nightly.
Even when other factors -- parental obesity, participation in sports, family income and hours spent watching television, using a computer or playing video games -- were factored into the equation, the study found that sleep proved to be the "best predictor" of body weight, especially for boys, according to Angelo Tremblay, professor of physiology and nutrition at Laval and the study's lead author.
Add this report to a number of others, including a long-term study of about 7,000 children published last year by British researchers. They found that the length of time children slept as preschoolers independently predicted their weight at age 7. As the team noted in the British Medical Journal, children who slept less than 11 hours a night at age 21/2 years were significantly more likely to be obese at age 7 than those who slept 12 hours or more.
It's a hormone thing
Sleep counts for adults too. A German study of 8,000 men and women found that sleeping difficulties were linked with an increased risk of obesity and with developing type 2 diabetes -- the kind that is related to body weight. Harvard University's Nurses' Health Study also has shown that participants who slept less than five hours per night had an increased risk of developing type 2 diabetes over a 10-year period.
How might sleep affect body weight and development of diabetes? That's still not known, but there are some promising leads. Among the leading suspects: leptin, ghrelin and cortisol -- hormones altered by lack of sleep and known to regulate appetite.
Just how much skipping sleep may affect body weight is illustrated by a small study of healthy, lean young men in a sleep lab at the University of Chicago. During the 16-day study, missing a couple of hours of sleep per night wreaked havoc with leptin and cortisol levels. That, in turn, fueled hunger. "Their bodies were screaming 'famine' despite the fact that they didn't need to eat," notes Eve Van Cauter, lead author of the study. "They responded as if they were missing about 1,000 calories a day."
Skipping sleep also pushed these otherwise healthy young men into impaired glucose tolerance, a step toward full-blown diabetes. During the study, their insulin and blood sugar levels suddenly resembled those of adults 65 to 80 years old. The good news: Hunger, hormones and blood sugar returned to normal with sleep.
A common denominator
In the past 20 years, the average amount of nightly sleep for adults has declined about 1 1/2 hours per night. Compare that to the national rise of body weight "and they are an exact mirror image," notes Van Cauter, just a hint that chronic sleep loss may play a role in the obesity epidemic.
How much of a role is uncertain. Lack of sleep also can be a sign of stress, which also fuels appetite. As Astrup writes, "it may prove difficult to disentangle the causes of impaired sleep from its effects."
Besides, there could be something simpler at work: "When we sleep more," Astrup notes, "we simply have less time in which to eat."
No studies have yet systematically tested the weight-loss benefits of napping, but research suggests that naps help make up for sleep loss in other ways. So until scientists sort it out, sleep experts say to nap, if possible, on those days when nightly sleep is cut short. Adults need about eight hours per night; children require 10 to 12 hours; and teens need eight to nine hours.
Boosting physical activity not only helps improve sleep, but also increases energy, decreases stress, elevates mood and increases mental performance. Plus, it may dampen hunger.