Establishing the optimal body mass index - body esteem relationship in young adolescents

Background This study sought to compare the utility of either inverted body mass index or body mass index to optimise the relationship with body esteem in young adolescents. Design: The study was cross sectional in design and assessed body esteem and weight status in756 young adolescents (394 boys, 362 girls, mean age ± S.D. 11.4 ± 1.6 years). Methods Body esteem was determined using the body esteem scale for children. Height and body mass were measured directly. Body mass index was determined as kg/m2 and iBMI as cm2/kg. Results Results indicated that the association between iBMI and body esteem was curvilinear in nature and iBMI was the better predictor of body esteem (P = .001) predicting 21.3% of the variance in body esteem scores compared to 20.5% using BMI (P = .001). When split by gender, the curvilinear relationship was still evident but significantly different between boys and girls although iBMI remained a better predictor of body esteem compared to BMI in both boys and girls. The peak differed between gender groups with the association between iBMI and body esteem peaking at 642 cm2/kg for boys and 800.64 cm2/kg for girls. Conclusion This study suggests that iBMI is a better predictor of body esteem in young adolescents, and that the association between body esteem and iBMI is curvilinear in nature. However, the peak of body esteem scores occured at a lower degree of leanness for boys compared to girls and indicated that the point at which body esteem scores are highest for girls is at a point of extreme leanness whereas the peak for boys was within the values considered as ‘normal’ on the leanness to obesity continuum. iBMI may therefore be a useful measure of leanness for future studies examining the association between overweight/obesity and body esteem in young adolescents.