Agreement between ultrasound protocols for the estimation of body fat percentage: Comparison to a four-compartment model

The purpose of this study was to examine the agreement between body fat percentage (%Fat) estimates derived from a standardized ultrasound protocol (%Fat_IASMS), a commonly used skinfold (SKF)-site-based ultrasound protocol (%Fat_JP), and a criterion four-compartment (4C) model (%Fat_4C). For the ultrasound protocols, all measurement sites were marked, measured and analyzed by the same evaluator. Subcutaneous adipose tissue (SAT) thickness was measured manually at the region where the muscle fascia was parallel to the skin and the average value per measurement site was used to calculate body density and subsequently %Fat. A repeated-measures analysis of variance with a priori planned contrasts was used to compare %Fat values between the 4C criterion and both ultrasound methods. Small nonsignificant mean differences were observed between %Fat_IASMS (18.82 ± 14.21%Fat, effect size [ES] = 0.25, p = 0.178), %Fat_JP (18.23 ± 13.32%Fat, ES = 0.32, p = 0.050) and the %Fat_4C criterion (21.70 ± 7.57%Fat); however, %Fat_IASMS did not yield a smaller mean difference than the %Fat_JP (p = 0.287). Additionally, %Fat_IASMS (r = 0.90, p < 0.001, standard error of the estimate [SEE] = 3.29%) and %Fat_JP (r = 0.88, p < 0.001, SEE = 3.60%) were strongly correlated with the 4C criterion, however, %Fat_IASMS did not yield better agreement than %Fat_JP (p = 0.257). Despite slightly underestimating %Fat, both ultrasound techniques demonstrated Good—Very Good agreement with the 4C criterion, with comparable mean differences, correlations, and SEE. The International Association of Sciences in Medicine and Sports (IASMS) standardized protocol using manual calculations of SAT was comparable to the SKF-site-based ultrasound protocol when compared to the 4C criterion. These results indicate that the IASMS (with manually measured SAT) and SKF-site-based ultrasound protocols may be of practical use to clinicians.