"Lack of Sleep…" Source: Nicole Ostrow , Apr
11, 2012. Lack of Sleep May Lead to Obesity, Harvard Study
Suggests." Bloomberg News ( Retrieved from: http://www.bloomberg.com/news/2012-04-11/lack-of-sleep-may-lead-to-obesity-harvard-study-suggests.html
)
According to a Harvard study published in the
journal Science Translational Medicine:
Lack of sleep or erratic slumber from working
late-night shifts or travel may lead to diabetes and obesity.
In a trial of 21 men and women observed in a
sleep laboratory, those allowed only 5.6 hours of sleep in a 24-hour
period over three weeks had a slowdown in their metabolism and a
reduction in insulin production.
Slowing of the metabolism and reducing insulin
production can lead to weight gain and increased blood sugar.
Sleeping, eating and being active at times that
are at odds with the body's internal clock, called circadian
disruption, may raise the risk of diabetes and obesity as metabolic
changes occur, said Orfeu Buxton, the lead study author.
"We disrupted not just the timing of sleep but
the timing of meals, so it seems that eating meals at an unusual
time may also play a role," said Buxton, as assistant professor at
Harvard Medical School.
About 15 percent of full-time wage and salary
workers in the U.S. work an alternative shift, 4.7 percent work
evenings, 3.2 percent work nights and 2.5 percent work rotating
shifts, according to 2004 data from the Bureau of Labor Statistics,
the latest year for which data is available. Allowing workers to
stay in the same shifts for longer periods rather than changing
every few days may help them stave off health problems, Buxton said.
Researchers in the study followed healthy men
and women who were kept in a controlled environment. The amount of
sleep, when the sleep occurred, activities and diet were regulated.
For three weeks they were only allowed to sleep
for 5.6 hours in any 24-hour period. The sleep occurred at all times
of the day and night to help copy the schedule of rotating shift
workers.
Chronic sleep restriction and disruption to the
body's internal clock caused about a one-third decrease in insulin
secretion after a standard meal, the researchers found. Too little
insulin raises glucose levels in the body for longer periods of
time, and may increase the risk of diabetes, Buxton said.
He speculated that the clock in the pancreas,
which regulates insulin, similar to the circadian clock in the
brain, might also be disrupted making it not ready to secrete enough
insulin to the body at the new time, he said.
Participants also experienced an 8 percent drop
in resting metabolism, the amount of calories burned by the body's
muscle excluding exercise. The slowed metabolism could contribute to
a 12.5-pound increase in weight over a year if there were no changes
in exercise levels or food intake. That weight gain may lead to
obesity and elevate diabetes risk, the authors said.
Buxton said changes in the body's clock and
lack of sleep may cause the body to conserve energy when it isn't
necessary. Those who don't get enough sleep also don't exercise, eat
more and eat more inappropriate foods, he said.
The effects were reversible after nine days of
recovery sleep and the readjustment of the body's internal clock,
the study showed.
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