Sleep isn’t just for the brain, concludes a study from the University of Chicago, which found that not getting enough shut-eye is harmful to fat cells, reducing by 30% their ability to respond to insulin, a hormone that regulates energy.
The research, published in the Oct. 16 issue of the Annals of Internal Medicine, connects sleep loss to the disruption of a person’s ability to regulate energy, a process that can lead to weight gain, diabetes and other health problems. The study suggests that sleep’s role in energy metabolism is at least as important as it is to brain function.
“We found that fat cells need sleep to function properly,” says study author Matthew Brady, associate professor of medicine at the University of Chicago. “Many people think of fat as a problem, but it serves a vital function. Body fat stores and releases energy.”
The two-part study included six men and one woman. In part one of the research, the volunteers spent 8.5 hours a night in bed for four consecutive nights. In the other part, they spent 4.5 hours in bed for four nights. Their food intake was identical under both study conditions. After the fourth night, researchers tested each volunteer’s total-body insulin sensitivity.
During the short sleep cycles, the insulin sensitivity of fat cells decreased by 30%—comparable to the difference between the cells of obese and lean people. Researchers also found that the sleep-deprived participants had a decreased response to insulin.
“Some people claim they can tolerate the cognitive effects of routine sleep deprivation,” says study co-author Eve Van Cauter, the Frederick H. Rawson Professor of Medicine at the University of Chicago. “In this small but thorough study, however, we found that seven out of seven subjects had a significant change in insulin sensitivity. They are not tolerating the metabolic consequences.”