Objective: To determine the accuracy of foot-to-foot bioelectrical impedance 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-ray absorptiometry (DEXA)-derived body composition in a multi-ethnic group of 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-free 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 overestimated DEXA-PBF by a mean of 2.53%. The correlation between six anthropometric indices (body mass index (BMI), ponderal index, Chinn's weight-for-height index, BMI standard deviation score, weight-for-length index and Cole's weight-for-height index) and DEXA were also examined. The correlation of these 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 estimation of FFM, FM and PBF. Foot-to-foot BIA is an accurate technique in the measurement of body composition.