Bioelectrical impedance analysis to assess body composition in obese adult women: The effect of ethnicity

Abstract

OBJECTIVE: To examine whether the accuracy of bioelectrical impedance analysis (BIA) to estimate body composition in overweight women is affected by the ethnicity of the individuals.

DESIGN: Cross-sectional design to compare body composition estimated by BIA to body composition measured by dual energy x-ray absorptiometry (DEXA), which was the reference method.

SUBJECTS: One hundred twenty three overweight women participated in this study, of which 43 women were African-American (aged 37.2±5.6 y; BMI, 32.3±4.9 kg/m²) and 80 were Caucasian (aged 36.1±5.7 y; BMI, 31.9±3.5 kg/m²).

MEASUREMENTS: Body composition was estimated from BIA using both a generalized and an obesity-specific equation. These estimations were compared to body composition measured by DEXA, which was the reference method.

RESULTS: The generalized BIA equation underestimated lean body mass (LBM) by 2.6±3.1 kg in Caucasian women and 0.4±3.2 kg in African-American women, with the difference between the ethnic groups being significant (P<0.001). The obesity-specific equation underestimated LBM in Caucasians by 0.9±3.1 kg and overestimated LBM in African-Americans by 1.2±2.8 kg (P<0.001). An ethnic-specific equation is proposed, and cross-validation of this equation indicates that it provides a reasonable estimate of body composition in overweight women.

CONCLUSIONS: The accuracy of BIA to estimate body composition appears to be affected by the ethnicity of the individual. Therefore, an ethnic-specific equation for overweight women is proposed. However, further validation of this prediction model in an ethnically diverse population is necessary.