ESTIMATION OF BODY-COMPOSITION FROM BIOELECTRICAL-IMPEDANCE OF BODY SEGMENTS - COMPARISON WITH DUAL-ENERGY X-RAY ABSORPTIOMETRY

In twenty-eight healthy subjects, ten men and eighteen women, with a r ange in body mass index (BMI) of 17.9-31.6 kg/m2 and an age range 20-6 0 years, body composition was estimated by dual-energy X-ray absorptio metry (DEXA), skinfold anthropometry (SFA) and bioelectrical impedance analysis (BIA) of the 'whole body' and body segments. In thirteen sub jects muscle mass was also estimated by 24 h urinary creatinine excret ion. The relationship between fat-free mass (FFM) determined by DEXA a nd the impedance index of each body segment (calculated as length2/imp edance (Z)) was analysed. The strongest correlation was between FFM (D EXA) and height2/'whole-body' Z (Z(w)) (r 0.97 for the combined sexes, standard error of estimate (SEE) 2.72 kg). Separate prediction equati ons were found to be necessary for males and females when estimating F FM from BIA measurement of the arm (for men, r 0.93, SEE 1.98 kg; for women, r 0.75, SEE 2.87 kg). Muscle mass derived from 24 h creatinine excretion showed weak correlation with FFM (DEXA) (r 0-57, P = 0.03) a nd no correlation with FFM (SFA). FFM (SFA) correlated well with both FFM (DEXA) (r 0-96, SEE = 3.12 kg) and with height2/Z(w) (r 0.92, SEE 4.52 kg). Measurement of the impedance of the arm offers a simple meth od of assessing the composition of the whole body in normal individual s, and it appears comparable with other methods of assessment.