In this study, 29 adolescents (14 lean and 15 obese) completed the 12-week moderate aerobic exercise program. During the exercise sessions, subjects worked out on a treadmill, elliptical or bicycle. The goal of each exercise session was to get the participants' heart rate to increase to at least 70 percent of their maximum capacity. Glucose and insulin concentrations were measured both before and after the exercise program. Cardiovascular fitness was determined using an oxygen consumption test which consists of measuring oxygen uptake of the participant during a treadmill exercise where speed and incline is increased every three minutes until the subject reaches his maximum exercise capacity.

"Many studies include both diet and exercise interventions, which makes it difficult to determine which intervention is most effective and best accepted by adolescents," said Sunehag. "Our findings show that exercise alone can increase fitness and improve insulin sensitivity, making an aerobic program like the one used in this study a potential useful tool in preventing obesity-related illnesses."

Other researchers working on the study include Gert-Jan van der Heijden of Baylor College of Medicine in Houston, Tex.; Gianna Toffolo and Erica Manesso of the University of Padova in Padua, Italy; and Pieter Sauer of the University of Groningen in The Netherlands.The article, "Aerobic exercise increases peripheral and hepatic insulin sensitivity in sedentary adolescents," will appear in the November 2009 issue of JCEM.

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