Losing Sleep, Gaining
By Maggie Fox, Health and
Science Correspondent 12/06/04t
WASHINGTON (Reuters) -
put on a few extra pounds may be able to blame a lack of sleep for
the added weight, according to two separate studies published on
Losing sleep can
raise levels of hormones linked with appetite and eating behavior,
the researchers said.
In one study, people who slept only
four hours a night for two nights had an 18 percent reduction in leptin, a hormone that tells the brain there is no need for more
food, and a 28 percent increase in ghrelin, which triggers hunger.
The young men in the study also
tended to eat more sweet and starchy foods when sleep was cut short.
"We don't yet know why food choice
would shift," said Eve Van Cauter, a professor of medicine at the
University of Chicago who led the study. "Since the brain is fueled
by glucose, we suspect it seeks simple carbohydrates when distressed
by lack of sleep."
"This is the first study to show
that sleep is a major regulator of these two hormones and to
correlate the extent of the hormonal changes with the magnitude of
the hunger change." Van Cauter said. "But we are finding that people
tend to replace reduced sleep with added calories ..."
Van Cauter and colleagues wrote in
the Annals of Internal Medicine that they studied 12 healthy men in
their early 20s. They measured circulating levels of leptin and
ghrelin before the study, after two nights of only four hours in
bed, and after two nights of ten hours in bed.
"We were particularly interested in
the ratio of the two hormones -- the balance between ghrelin and
leptin," Van Cauter said. After four hours of sleep, the ratio of
ghrelin jumped 71 percent compared to a night when the men slept
The sleep-deprived men chose candy,
cookies and cake over fruit, vegetables or dairy products.
A second study found that the less
people sleep, the more they weigh, using a measure called body mass
index, which scales weight to height. It also found lower leptin
levels and higher ghrelin levels in people who slept less.
Dr. Emmanuel Mignot of Stanford
University in California and colleagues examined 1,000 people in the
Wisconsin Sleep Cohort Study, measuring each person's sleep habits,
as well as sleep on the night before the exam and leptin and ghrelin
They found people who consistently
slept five hours or less per night had on average 14.9 more ghrelin
and 15.5 percent lower leptin levels than those who slept eight
hours a night.
"Our results demonstrate an
important relationship between sleep and metabolic hormones," the
researchers wrote in the Public Library of Science Medicine journal.
Ask any new parent and they'll be happy to confirm these
results and tell you how much their waist has expanded that first
year of birth!