Tracking and association of body weight and body fat in elementary school children

Abstract

Background: Excess body fat is a major health risk to various chronic diseases. Given the ease of measurement and low cost of body weight and height, body mass index (BMI) has been widely used to estimate body fatness. The present study evaluates the accuracy of BMI as an indicator of body fatness, measured via bioelectric impedance (BIA) during the elementary school years in Austrian children. Methods: Out of six schools in Innsbruck, Austria, anthropometric assessments and BIA measurements were performed in 199 children starting elementary school in fall 2013. Annual follow-up measurements were performed by the same measurement team until 4th grade. Results: Cross-sectional analyses revealed a significant moderate correlation between BMI and percent body fat (%BF) (r=0.61) and an AUC of 0.88 indicated high accuracy of BMI as an indicator for body fatness. There was also high tracking of BMI and %BF over the 4-year observation period (r ≥ 0.84). Follow-up measurements further showed that the association between BMI and %BF increased with age during the elementary school years (rgrade 4 = 0.78; AUCgrade 4 = 0.96). Conclusions: Given the health problems associated with excess body fat an accessible and accurate assessment of body composition is warranted. The BMI provides a low-cost and easily administered surrogate measure of body fatness in elementary school children for initial screening. Children considered at risk, however, may require more elaborate assessments that directly measure fat mass and fat-free mass.