Inverted BMI rather than BMI is a better predictor of DEXA determined body fatness in children

This study compared body mass index (BMI) and inverted BMI (iBMI) as predictors of body fatness in 177 Portuguese children (149 girls and 96 boys) aged 7–16 years. Participants undertook measures of height and body mass from which BMI (kg/m2) and iBMI (cm2/kg) were determined. Maturation was determined via self-report and fat mass index (FMI, kg/m2) via dual-energy X-ray absorptiometry. Significant relationships were evident between BMI and iBMI and FMI (both P=0.0001). BMI was not normally distributed (P=0.0001) but iBMI was (P>0.05). Analysis of covariance identified that BMI and iBMI, controlling for maturation, were both significant predictors of FMI (both P=0.0001) but that iBMI predicted a slightly greater amount of the variance (adjusted R2=0.970) compared with BMI (adjusted R2=0.968). This study suggests that iBMI is a similar proxy for body fatness compared with BMI in children.