A very large study has found a surprisingly strong link between the
amount of shut-eye people get and their risk of becoming obese.
Those who got less than four hours of sleep a night were 73 percent
more likely to be obese than those who got the recommended seven to nine
hours of rest, scientists discovered. Those who averaged five hours of
sleep had 50 percent greater risk, and those who got six hours had 23
percent more.
"Maybe there's a window of opportunity for helping people sleep
more, and maybe that would help their weight," said Dr. Steven
Heymsfield of Columbia University and St. Luke's-Roosevelt Hospital in
New York.
He and James Gangwisch, a Columbia epidemiologist, led the study and
are presenting results this week at a meeting of the North American
Association for the Study of Obesity.
They used information on about 18,000 adults participating in the
federal government's National Health and Nutrition Examination Survey,
or NHANES, throughout the 1980s. The survey includes long-term follow-up
information on health habits, and researchers adjusted it to take into
account other things that affect the odds of obesity, like exercise
habits, so that the effects of sleep could be isolated.
It seems "somewhat counterintuitive" that sleeping more
would prevent obesity because people burn fewer calories when they're
resting, Gangwisch said.
But they also eat when they're awake, and the effect of chronic sleep
deprivation on the body's food-seeking circuitry is what specialists
think may be making the difference in obesity risks.
"There's growing scientific evidence that there's a link between
sleep and the various neural pathways that regulate food intake,"
Heymsfield said.
Sleep deprivation lowers leptin, a blood protein that suppresses
appetite and seems to affect how the brain senses when the body has had
enough food. Sleep deprivation also raises levels of grehlin, a
substance that makes people want to eat.
It also hurts "executive function" — the ability to make
clear decisions, said Dr. Philip Eichling, a sleep and weight-loss
specialist at the University of Arizona who also is medical director of
the Canyon Ranch, a spa in Tucson that offers health and weight
management programs, especially for business executives.
"One of my treatments is to tell them they should move from six
hours to seven hours of sleep. When they're less sleepy, they're less
hungry," he said.
Eichling had no role in the new study but said it gives important
evidence for a long-suspected theory in the field. Americans average
only a little more than six hours of sleep a night, and one report a few
years ago even suggested that the growing prevalence of sleep
deprivation might be responsible for the growing obesity epidemic, he
said.
