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By Nanci Hellmich, USA TODAY
Scientists have known for years that not getting enough sleep
makes people tired and cranky. It can raise their risk of being in
a traffic accident, or making mistakes at work and home. But
preliminary results of a new study also suggest that sleep
deprivation may promote weight gain, at least for the short term.
Eve
Van Cauter, a professor of medicine at the University of Chicago,
and colleagues are studying more than 30 young men and women who
are lean and fit. Some of them sleep less than 6 hours a night;
they are categorized as short sleepers. The others sleep 7 to 8
hours a night and are labeled normal sleepers.
So
far, results of the study indicate that the short sleepers have an
impaired ability to dispose of glucose using insulin, which may
put them on the pathway to obesity, says Van Cauter, who will
present the study at a professional sleep meeting in June.
Researchers don't know whether people who have short-changed
themselves of sleep on a regular basis can improve insulin
sensitivity by sleeping more.
In
a previous study, Van Cauter and colleagues followed 11 men in
their 20s who were allowed to sleep only four hours a night. After
a week, the men's metabolic levels and their ability to process
carbohydrates had diminished. In the long term, such alterations
could foster obesity, diabetes, high blood pressure and mental
sluggishness, Van Cauter says.
The
sleep loss affected many biological processes, including thyroid
function and levels of the stress hormone cortisol, which was
abnormally high in the evening in the sleep-deprived men, she
says. But after the men made up for the sleep loss, they showed no
signs of permanent damage, and their metabolic levels returned to
normal. "The changes could be reversed in young men submitted to
just one week of sleep loss, but we do not know whether the
alterations can be reversed if sleep loss is more chronic," she
says.
Van
Cauter is not sure how lack of sleep might lead to weight gain.
"We believe it's quite complex," she says. It may be a
physiological response to the stress hormone cortisol, she says.
It's also possible because the brain senses a lack of energy and
encourages the person to eat, even if they've had enough calories
for the day, she says.
James Walsh, executive director of the Sleep Medicine and Research
Center at St. Luke's Hospital in St. Louis, says this work "is
significant because researchers are finally assessing the impact
of sleep loss on basic physiology, and I think that's a major step
forward."
Obesity researcher George Blackburn, of Harvard-affiliated Beth
Israel Deaconess Medical Center in Boston, says: "A good night's
sleep is important to weight management, appetite and hunger
control. You need to awaken refreshed so you can plan healthy
eating and exercise for each day."
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