Bioelectrical impedance method for body composition assessment in Japanese adult females and its cross-validity / 体力科学

ABSTRACT

Several prediction equations for estimating body composition of Japanese men and women have recently been developed using a linear regression model with a combination of impedance and anthropometric measurements as independent variables. The purpose of this study was to determine the cross-validity of body density (Db) estimated from bioelectrical impedance (BI) and skinfold thickness (ST) methods in comparison with underwater weighing (UW) as a criterion reference method. Percentage body fat (%BF) was derived from Db according to the equation Brozek et al. Fifty-seven healthy Japanese women, aged 19 to 57 years, volunteered to participate in the study. Impedance was measured by use of a portable four-terminal impedance plethysmograph (Selco, SIF-891) . %BF derived from the BI method (r=0.860-0.875) was correlated with hydrodensitometrically determined %BF to a greater extent than %BF obtained using the ST method (r=0.7330.758) or ultrasound method (r=0.536-0.721) . Correlations of various anthropometric indices (r=0.655-0.691) with hydrodensitometrically determined %BF were even lower. It was noteworthy, however, that mean %BF derived from existing BI equations differed significantly from hydrodensitometrically determined mean %BF. Therefore, we attempted to develop a new equation that was applicable to Japanese adult women as follows: Db=1.1613-0.1038 (Wt⋅Z ) /Ht<SUP>2</SUP>, where Wt=weight in kg, Z=impedance in ohms, and Ht=height in cm. The prediction accuracy of this equation was r=0.866 or SEE=0.0077 g/ml. Cross-validation of this equation on a different sample (122 Japanese women, aged 18 to 59 years) revealed a correlation of r=0.869 in terms of %BF, SEE=3.2%, and no significant difference between estimated %BF and the criterion. We suggest that the BI method is one of the most convenient, valid means of assessing human body composition, and that the newly developed BI equation could be useful particularly when the subjects are Japanese adult women in their late teens to fifties.