Validation of simple epidemiological or clinical methods for the measurement of body composition in young children

The present study aimed to determine the validity of simple epidemiological and clinical methods for the assessment of body fatness in preschool children. In 89 children (42 boys, 47 girls; mean age 4.1 SD 1.3y) measures of body fatness were made using total body water (TBW), dual energy x-ray absorptiometry (DXA), air displacement plethysmography (BODPOD) and skinfold thickness. Methods were compared by Bland–Altman analysis using TBW as the reference method, and by paired comparisons and rank order correlations. Bias for DXA was +1.8% body fat percentage units (limits of agreement +15.5% to -11.9%), bias for BODPOD was -3.5% (limits of agreement +18.9% to -5.9%) and bias for skinfolds using the Slaughter equations was -6.5% (limits of agreement +10.0% to –23.1%). Significant rank order correlations with TBW measures of fatness were obtained for DXA estimates of fatness (r=0.54, P=0.01), but not for estimates of fat by skinfold thickness (r=0.20, P=0.2) or BODPOD (r=0.25, P=0.1). Differences between both DXA and BODPOD and the reference TBW estimates of body fatness were not significant (P=0.06 and P=0.1 respectively); however, the difference in estimated body fatness between skinfold thickness and TBW was significant (P<0.001). Estimates of body fatness in preschool children were inaccurate at the level of the individual child using all the methods, but DXA might provide unbiased estimates and a means of making relative assessments of body fatness.