Body composition prediction equations based on bioelectrical impedance and anthropometric variables for Japanese obese women

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Abstract
The tetrapolar bioelectrical impedance (BI) technique has been proposed as a convenient, valid approach to estimate body composition in normal, healthy adults. However, the validity of the BI technique for obese individuals is undetermined. The purpose of this study was to determine the validity of body composition estimated from the BI method when compared to underwater weighing with correction for residual volume, and to develop a convenient, useful equation that would sufficiently predict body composition of Japanese obese women. The order of assessing body composition was randomized for each subject. The subjects were 75 moderately or mildly obese women with a body fat content of 25.1–60.1%, aged 18–68 years. Among 12 independent variables which were arbitrarily selected as possible predictors of hydrodensitometrically determined body density (Db), BM Z/S2 was the best predictor (r = 0.803, n = 53), where BM = body mass (kg), Z = impedance (ohms), and S = stature (cm). When chronological age was added in a multiple regression analysis, Db was derived with higher accuracy (r = 0.878) with an SEE of 0.0064 g/cm3. The linear multiple regression equation constructed for predicting the Db was, for instance, Db = 1.1171 – 0.0535BM Z/S2 – 0.0003 Age – 0.0005T, where T = triceps skinfold thickness (mm). Three equations developed in the present study were then cross-validated in a different sample (n = 22) of obese women. The results indicated that the above equation had the lowest SEE (0.0070 g/cm3). We suggest that body composition of Japanese obese women can be predicted with relatively high accuracy by a combination of BM Z/S2 with age and the triceps skinfold thickness.