Is Waist Circumference a Better Predictor of Insulin Resistance Than Body Mass Index in U. S. Adolescents?

Purpose: To determine whether waist circumference (WC) is a better predictor of insulin resistance (IR) than body mass index (BMI) in U.S. adolescents aged 12-18 years. Methods: Using data from the National Health and Nutrition Examination Survey 1999-2002, we evaluated an ethnicaly diverse sample of 1,571 adolescents with regard to BMI, WC, and fasting glucose and insulin levels. Children were classified as having IR if they had a homeostasis model assessment of insulin resistance (insulin [U/mL] x glucose [mmol/L]/22.5) of greater than 4.39. We created receiver operating characteristic curves predicting IR across various thresholds of WC and BMI, and area under the curve was compared. Results: The prevalence rate of IR in the study population was 11.8%. Measures of test performance (sensitivity and specificity) for predicting IR were similar for abnormal BMI and WC thresholds; that is, thresholds of BMI 85th% and WC75th% and thresholds of BMI 95th% andWC90th% were quite similar. There were no significant differences in area under the curve for WC versus BMI (.85; 95% CI, .83-.88; p = .84) either for the overall population or for specific racial groups. Conclusions: WC does not seem to provide a distinct advantage over BMI for identifying adolescents with IR. (C) 2011 Society for Adolescent Health and Medicine. All rights reserved.