Why a good night's sleep helps keep diabetes, obesity at bay

A new study has shed light on the links between sleep loss and diabetes indicating that lack of sleep can elevate levels of free fatty acids in the blood, accompanied by temporary pre-diabetic conditions in healthy young men.

The study conducted at University of Chicago Medical Center suggested that something as simple as getting enough sleep could help counteract the current epidemics of diabetes and obesity.

Esra Tasali, MD, assistant professor of medicine at the University of Chicago and senior author of the study, said that at the population level, multiple studies have reported connections between restricted sleep, weight gain, and type 2 diabetes and experimental laboratory studies, like theirs, helped them unravel the mechanisms that may be responsible.

The researchers recruited 19 healthy male subjects between the ages of 18 and 30. These volunteers were monitored through two scenarios in randomized order. In one, they got a full night's rest i.e. 8.5 hours in bed (averaging 7.8 hours asleep) during four consecutive nights. In the other, they spent just 4.5 hours in bed (averaging 4.3 hours asleep) for four consecutive nights. The two studies were spaced at least four weeks apart.

Each subject's sleep was carefully monitored, diet was strictly controlled and blood samples were collected at 15 or 30 minute intervals for 24 hours, starting on the evening of the third night of each study. The researchers measured blood levels of free fatty acids and growth hormone, glucose and insulin, and the stress hormones noradrenaline and cortisol. After four nights in each sleep condition, an intravenous glucose-tolerance test was performed.

Study's lead author, Josiane Broussard, PhD, said that curtailed sleep produced marked changes in the secretion of growth hormone and levels of noradrenaline-which can increase circulating fatty acids and the result was a significant loss of the benefits of insulin. This crucial hormone was less able to do its job. Insulin action in these healthy young men resembled what we typically see in early stages of diabetes.

The researchers found that after three nights of getting only four hours of sleep, blood levels of fatty acids, which usually peak and then recede overnight, remained elevated from about 4 a.m. to 9 a.m. As long as fatty acid levels remained high, the ability of insulin to regulate blood sugars was reduced.

The study is published online in Diabetologia, the journal of the European Association for the Study of Diabetes.