Monday, November 19, 2012

Short sleep, blood sugar, and hormone regulation

Lots of hoopla in the news about relationship between short sleep and obesity. Studies are showing that reduced sleep leads to more eating. In this month's Sleep Journal, St-Onge et al did a study to test the effects of sleep duration on hormones and metabolites involved in energy balance regulation.

They studied normal weight, health men and women in the sleep lab. They had them sleep for 4 hours per night x 3 nights and then three weeks later let them sleep 9 hours per night x 3 nights. During each three night portion, their food intake was strictly controlled and monitored.

Results showed no effect of short sleep on glucose, insulin, or leptin levels, as previously shown in other studies. The authors point out that those other studies allowed participants to eat at will, rather than the limited eating allowed in the current study. It may be that overeating in the other studies is what produced the blood glucose changes seen.

In this study, short sleep caused increases in ghrelin in men, but not in women. Ghrelin can increase appetite. Women had reduced levels of GLP-1, but men did not. GLP-1 is known to increase satiety. So men and women may overeat for different reasons in context of short sleep duration if allowed to eat whenever and as much as they want.

It is difficult to extrapolate these results to overweight individuals, who may be metabolically different than the healthy participants in this study.

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