In Nonobese Girls, Waist Circumference as a Predictor of Insulin Resistance Is Comparable to MRI Fat Measures and Superior to BMI

Abstract

Objective: The aim of this study was to investigate the degree to which waist circumference (WC), body mass index (BMI), and magnetic resonance imaging (MRI)-measured abdominal fat deposition predict insulin resistance (IR) in nonobese girls of diverse racial and ethnic backgrounds. Methods: Fifty-seven nonobese girls (12 African-American, 16 Hispanic White, and 29 non-Hispanic White girls) aged 11-14 years were assessed for WC, MRI hepatic proton density fat fraction, visceral and subcutaneous adipose tissue volume, BMI Z-score, fasting insulin, homeostasis model of assessment (HOMA)-IR, adiponectin, leptin, sex hormone-binding globulin, high-density lipoprotein cholesterol, and triglycerides. Results: Univariate and multivariate analyses adjusted for race and ethnicity indicated that only WC and visceral adipose tissue volume were independent predictors of fasting insulin and HOMA-IR, while hepatic proton density fat fraction, BMI Z-score, and subcutaneous adipose tissue volume were dependent predictors. Hispanic White girls showed significantly higher mean fasting insulin and HOMA-IR and lower sex hormone-binding globulin than non-Hispanic White girls (p < 0.01). Conclusions: In nonobese girls of diverse racial and ethnic backgrounds, WC, particularly when adjusted for race or ethnicity, is an independent predictor of IR comparable to MRI-derived measurements of fat and superior to the BMI Z-score.