ASSESSMENT OF BODY COMPOSITION IN JAPANESE FEMALES BY BIOELECTRICAL IMPEDANCE ANALYSIS

Abstract

Recently, bioelectrical impedance analysis systems (BIA) have become available for determination of human body composition. The validity of BIA has been found to be sufficiently in the American population. However, more work is needed to assess the validity and applicability of BIA to the Japanese population. The purposes of this study were (1) to test the validity of body composition measured by BIA in comparison with the underwater weighing criterion method, and (2) to develop a convenient equation that would reliably predict body composition using BIA and anthropometric measurements in Japanese females. The subjects were 226 Japanese women and girls aged 11 to 55 years (23.9±8.3) . Body impedance was measured using a tetrapolar electrode method, with a localized 800-μA and 50-kHz current injection (Selco SIF-881) . The percentage of body fat (%fat) estimated by BIA was significantly correlated with densitometrically determined %fat (r=0.793, Lukaski et al, method ; and r=0.800, Segal et al, method) . The magnitude of these correlations was substantially higher when compared with r=0.615 found between the skinfold thickness method and the criterion method. Absolute %fat values estimated by BIA were, however, significantly lower than those determined by the criterion method, thereby indicating the need for a more accurate method of assessing Japanese body composition. For this, we propose the use of D=1.1303-0.0726 (Wt×R/Ht²), where D=body density in g/ml, Wt=body weight in kg, R= (R²+Xc²) ^0.5 in ohms, and Ht=body height in cm. Lean body mass (LBM) and %fat predicted from this equation were correlated significantly (r=0.924 and r=0.799, respectively) with values determined by densitometry. The standard error of estimates of LBM and %fat resulted in figures of 1.9 kg and 3.7%, respectively. Thus we suggest that BIA is valid, convenient, and inexpensive, and that the prediction equation proposed in this study is useful for assessment of body composition in Japanese adult females.