Fatness, fitness, and insulin sensitivity among 7-to 9-year-old children

Objective: The purpose of this study was to examine the relationships among fatness and aerobic fitness on indices of insulin resistance and sensitivity in children. Research Design and Methods: A total of 375 children (193 girls and 182 boys) 7 to 9 years of age were categorized by weight as normal-weight, overweight, or obese and by aerobic fitness based on a submaximal physical working capacity test (PWC). Fasting blood glucose (GLU) and insulin (INS) were used to calculate various indices of insulin sensitivity (GLU/INS), the homeostasis model assessment (HOMA), and the quantitative insulin sensitivity check index (QUICKI). Surrogate measures of pancreatic 0 cell function included the insulinogenic index (INS/GLU) and the HOMA estimate of pancreatic beta-cell function (HOMA %,B). Results: Insulin sensitivity and secretion variables were significantly different between the normal-weight children and the over-weight and obese subjects. Fasting insulin (171), HOMA, QUICKI, and INS/GLU were significantly different between the over-weight and obese subjects. Likewise, the high fitness group possessed a better insulin sensitivity profile. In general, the normal-weight-high fit group possessed the best insulin sensitivity profile and the obese-unfit group possessed the worst insulin sensitivity profile. Several significant differences existed among the six fat-fit groups. Of particular note are the differences within BMI groups by fitness level and the comparison of values between the normal-weight-unfit subjects and the overweight and obese subjects with high fitness. Conclusions: The results indicate that aerobic fitness attenuates the difference in insulin sensitivity within BMI categories, thus emphasizing the role of fitness even among overweight and obese children.