Just a few nights of bad sleep is enough to throw the body’s metabolism into disarray, according to a new study published Monday in the journal Annals of Internal Medicine. The study shows that getting four hours of sleep a night for four nights made healthy people’s bodies resistant to insulin — a condition that is a common precursor of weight gain, diabetes and other serious health problems.
In a healthy body, when you take in sugar, insulin is released from the pancreas and travels throughout the body, signaling to cells that they should absorb some of that new glucose. But when the body becomes insulin-resistant, cells are less responsive to that signal, and glucose levels rise in the bloodstream. That can lead to diabetes, which causes damage to the eyes, kidneys and nerves, and has been linked to heart disease, stroke and premature death, according to the National Institutes of Health.
While several studies have shown that sleep affects diet and metabolism, most scientific research on sleep has focused on its role in normal brain function. But the new study — a collaboration among researchers who study sleep, diabetes and metabolism — finds troubling evidence that a lack of sleep can do serious damage to cells throughout the body by causing insulin resistance.
For the new study, researchers recruited seven healthy, active adults — six men and one woman. Each subject went through a four-night period in which they got eight or nine hours of sleep and four nights in which they only got four to five hours. After each four-night block, the subjects underwent a glucose challenge, in which glucose is injected into the body to test for insulin resistance. They also removed fat cells from each subject to test their biochemical response to insulin.
The changes were huge: After sleeping four hours a night for four nights, the subjects’ whole-body insulin response decreased by an average of 16%, and the fat cells’ insulin response decreased by 30%. The researchers say that those levels are akin to the levels seen in diabetics or the obese. And when the team looked at the biochemical markers of an insulin response in the fat cells they removed, they found it took three times as much insulin to cause a normal response after four nights of limited sleep.
The researchers admit they still have much to learn before they fully understand how sleep has this effect on fat cells or what effect it might have on otherwise healthy people. Nevertheless, the study provides just one more reason to get a good night’s sleep.
A team of experts at the University of Chicago conducted the study; the lead author, Josiane Broussard, is now a Society in Science-Branco Weiss fellow at Cedars-Sinai Medical Center in L.A.
You can read a summary of the study here.
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