A new study from the University of Colorado showed that adults who sleep less than 5 or 6 hours a night are more likely to be overweight, and the weight gain can be seen immediately.   16 healthy men and women were recruited for the 2-week study.  Half were allowed to sleep for 9 hrs and the other half got only 5 hrs of sleep.  Even though the 5 hr sleepers actually burned more calories, they gained an extra 2 lb. in the first week!  They found that not only did the light sleepers eat more calories, they overate carbohydrates and fats in particular and they also ate more at night and ate smaller breakfasts.

There was also a profound change in the ability of the cells to bind insulin, a metabolic change associated with diabetes and obesity.  “Metabolically, lack of sleep aged fat cells about 20 years,” said Matthew Brady, an associate professor of medicine at the University of Chicago and the senior author on the study.

The Well Column
 March 18, 2013, New York Times