Anthropometric indexes outperform bioelectrical impedance analysis-derived estimates of body composition in identification of metabolic abnormalities in morbid obesity

Abstract

BackgroundThe validity of anthropometric indexes in ascertaining the body composition (BC) in morbidly obese (MO) subjects has been questioned. Our objective was to evaluate, in MO subjects, whether bioelectrical impedance analysis (BIA) of BC is more closely associated with the metabolic syndrome (MS) and insulin resistance (IR) than are classic anthropometric measurements. The setting was a university hospital. MethodsThe association between anthropometric (body mass index, waist circumference [WC]) and BIA (total fat mass [FM] [percentage of FM], truncal FM, android FM) estimates of BC, MS, and IR was evaluated in 784 white MO subjects (212 men and 572 women). BIA estimates were calculated using equations specific for MO subjects developed by our own group and validated against dual energy x-ray absorptiometry. ResultsThe prevalence of the MS and IR was 78.6% and 88.6%, respectively. The body mass index was greater in women with the MS (P <.001) or IR (P <.001), and the WC was larger in subjects of both genders with the MS or IR (P <.001). Moreover, the WC correlated significantly with all the MS components (P <.05). In contrast, the percentage of FM, truncal FM, and android FM were significantly associated with the MS only in women. Stepwise logistic regression analysis demonstrated the WC as the only significant predictor of the MS or IR (both P <.001). Furthermore, receiver operating curve analysis showed WC was the most accurate BC parameter for the identification of subjects with the MS (area under the curve, WC = .681, P <.001) or IR (area under the curve, WC = .753, P <.001). ConclusionIn MO subjects, the BIA-derived indexes of total and central adiposity were not better predictors of the MS or IR than were traditional anthropometric measurements.