Foot-to-foot bioelectrical impedance analysis: a valuable tool for the measurement of body composition in children

OBJECTIVE: To determine the accuracy of foot-to-foot bioelectrical impedanc e analysis (BIA) and anthropometric indices as measures of body composition in children. DESIGN: Comparison of foot-to-foot BIA and anthropometry to dual-energy X-r ay absorptiometry (DEXA)-derived body composition in a multi-ethnic group o f children. SUBJECTS: Eighty-two European, NZ Maori and Pacific Island children aged 4. 9-10.9 y. MEASUREMENTS: DEXA body composition, foot-to-foot bioelectrical impedance, height, weight, hip and waist measurements. RESULTS: Using a BIA prediction equation derived from our study population we found a high correlation between DEXA and BIA in the estimation of fat-f ree mass (FFM), fat mass (FM) and percentage body fat (PBF) (r = 0.98, 0.98 and 0.94, respectively). BIA-FFM underestimated DEXA-FFM by a mean of 0.75 kg, BIA-FM overestimated DEXA-FM by a mean of 1.02 kg and BIA-PBF overesti mated DEXA-PBF by a mean of 2.53%. The correlation between six anthropometr ic indices (body mass index (BMI), ponderal index, Chinn's weight-for-heigh t index, BMI standard deviation score, weight-for-length index and Cole's w eight-for-height index) and DEXA were also examined. The correlation of the se indices with PBF was remarkably similar (r = 0.85 - 0.87), more variable with FM (r = 0.77 - 0.94) and poor with FFM (r = 0.41 - 0.75). CONCLUSIONS: BIA correlated better than anthropometric indices in the estim ation of FFM, FM and PBF. Foot-to-foot BIA is an accurate technique in the measurement of body composition.