Adding to a growing body of research linking poor sleep to weight gain, a new study found that losing just a few hours of sleep in a week—similar to the effects of jet lag or cramming for final exams—can lead to "almost immediate weight gain."
For the study, University of Colorado researchers studied 16 healthy men and women over a two-week period. They tracked their sleep, metabolism, eating habits, and even measured the amount of oxygen they used and carbon dioxide they produced by keeping them in specially designed rooms.
In the first week, half of the subjects were allowed to sleep nine hours a night, while the other half were forced to stay up until midnight and allowed only five hours of sleep. In the second week they reversed the sleeping schedules of the two groups.
The researchers found that sleeping only five hours actually increased participants' metabolism, leading them to burn an extra 111 calories a day. However, the revved up metabolisms of the sleep-deprived participants triggered them to eat 6% more calories than their well-rested counterparts—especially carbohydrates and fats.
"They ate a smaller breakfast and they ate a lot more after dinner," says lead author Kenneth Wright, adding that "[b]eing awakened during their biological night is probably why they ate smaller breakfasts."
As a result, the five-hour-a-night sleepers gained an average of two pounds in a week. When the sleep-deprived group was allowed to sleep nine hours, they began to lose the extra weight immediately (Parker-Pope, "Well," New York Times, 3/18).
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Daily roundup: March 19, 2013