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

Abstract

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. Using data from the National Health and Nutrition Examination Survey 1999-2002, we evaluated an ethnically 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] × 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. 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 WC 75th% and thresholds of BMI 95th% and WC 90th% 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. WC does not seem to provide a distinct advantage over BMI for identifying adolescents with IR.