Derived equation of bioelectrical impedance analysis validated by dual X-ray absorptiometry in assessing body composition of healthy Chinese adults

To derive more appropriate equations for measurement of percent body fat(%BF) by bioelectrical impedance analysis (BIA) on healthy Chinese adults, dual energy X-ray absorptiometry (DEXA) was used to validate BIA. A total of 193 healthy subjects of normal body size, including 112female (17-71 yr)and81 male (16-84 yr) were included. Weight, height, %BF estimated by BIA(BIA-FAT) and DEXA(DEXAFAT) were measured. BIA-FAT and DEXA-FAT showed high correlation (for male r=0.6466, for female r=0.8548). Mean BIA-FAT were 23.12% ±6.01% for male, and 30.78% ±3.56% for female; while mean DEXA-FAT were 20.79%+ 6.72%, 33.25%± 6.62 for male and female respectively For females, BIA underestimated %BF when it was higher than 26.57%, while underestimated that when body fat was less than 26.57% On the contrary, BIA overestimated body fat when it was higher than 14.7%, and underestimated %BF when body fat was lower than 14.7% for males. Stepwise regression was used to select variables for correction of equations. The derived model for female was: %BF = 12 6308+1 3022X(BIA-FAT)-0.1022 × (BIA-reactance) - 4.4331 × (height/weight) (r=0.9154) ; and for male : %BF = - 30.7007 + 1.4379 ×(BMI) + 0.6472x(BIA-FAT) 0.1724 ×(BIA-reactance) + 5.4979 x (height/weight) (r=0.8919) Those derived equations would aid the accuracy of measurement of body composition when BIA is used on healthy Chinese adults.