Even if they don't lose weight, a moderate aerobic exercise program can improve insulin sensitivity in obese adolescents who are sedentary.

Lack of sensitivity to insulin is one of the precursors to type 2 diabetes. Because obese people are insulin-resistant, their bodies attempt to control blood sugar by making the pancreas work harder to produce even more of the hormone. Eventually, the demand on the pancreas exhausts its insulin-producing beta cells, inviting the onset of type 2.

A study conducted by the Baylor University College of Medicine set out to find if moderate exercise alone, without any changes in diet or attempts to lose weight, could increase insulin sensitivity and redistribute fat in both lean and obese adolescents.

The study tracked 29 adolescents (15 obese and 14 lean) through a 12-week program of moderate aerobic exercise. Four 30-minute workouts per week involved working on a treadmill, bicycle, or elliptical, with the goal of increasing participants' heart rate to 70 percent of their maximum capacity.

The researchers measured blood glucose and insulin levels in the adolescents before and after each exercise session. By the end of the study period, participants in both weight groups had increased insulin sensitivity.

The findings show that even without altering dietary habits or shedding weight, obese adolescents can decrease their chances of acquiring type 2 diabetes with only two hours of exercise per week-a useful tool for healthcare professionals concerned about ways to treat pre-diabetes.

The same applies to sedentary lean adolescents: Even though their lack of body fat makes them less insulin resistant than their obese peers, their lack of physical activity can create high blood sugar levels that eventually trigger destructive demands on the pancreas.

The article, "Aerobic exercise increases peripheral and hepatic insulin sensitivity in sedentary adolescents," will appear in the November 2009 issue of The Endocrine Society's Journal of Clinical Endocrinology and Metabolism (JCEM).

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Source: Endocrine Society Press Release