The purpose of this study was to investigate the effects of fatness and fitness on insulin resistance (IR) and cardiovascular disease (CVD) risk factors among Korean adolescents. A total of 322 male high school students participated Departme nt of Sport and Leisure Studies, Yonsei University, Seoup, Republic of Korea Department of Sport and Leisure Studies, Yonsei University, Seoup, Republic of Korea in the cross-sectional part of the study. To determine the interaction of fatness and fitness levels on IR and CVD risk factors, subjects were stratified into four groups based on their body mass index (BMI) and cardio-respiratory fitness. Subjects who were in the high-fat category had significantly higher IR and CVD risk score than subjects in the low-fat category regardless of their fitness level. Subjects who were in high-fat-high-fit group showed significantly lower IR and CVD risk score than high-fat-low-fit group. Twenty-nine obese and unfit subjects participated in the intervention study. Twelve weeks of exercise training significantly reduced body weight (4.11+/-0.75 kg) and improved VO(2max) which resulted in a significant improvement in IR and CVD risk score (2.16+/-0.62 vs. 0.20+/-0.75). Interestingly, improvement in cardio-respiratory fitness and small reduction in body weight in relatively short-term significantly reduced the CVD risk score to the level of low-fat-low-fit subjects. Our results show the importance of fitness in determining IR and CVD risk factors among obese adolescents.

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