BODY-MASS INDEX AS A MEASURE OF ADIPOSITY AMONG CHILDREN AND ADOLESCENTS - A VALIDATION-STUDY

Objectives: To test the hypothesis that in a healthy pediatric populat ion body mass index (BMI) (kilograms per meter square) is a valid meas ure of fatness that is independent of age for both sexes, Methods: Tot al body fat (TBF) (in kilograms) and percent of body weight as fat (PB F) were estimated by dual energy x-ray absorptiometry (DXA) in 198 hea lthy Italian children and adolescents between 5 and 19 years of age. W e developed multiple regression analysis models with TBF and percent b ody fat as dependent variables and BMI, age, and interaction terms as independent variables. Separate analyses were conducted for boys and g irls. Results: BMI was strongly associated with TBF (R-2 = 0.85 and 0. 89 for boys and girls, respectively) and PBF (R-2 = 0.63 and 0.69 for boys and girls, respectively). Confidence limits an BMI-fatness associ ation were wide, with individuals of similar BMI showing large differe nces in TBF and in PBF. Age was a significant covariate in all regress ion models. Addition of nonlinear terms for BMI did not substantially increase the R-2 for TBF and PBF models in Lays and girls. Conclusion: Our results support the use of BMI as a fatness measure in groups of children and adolescents, although interpretation should be cautious w hen comparing BMI across groups that differ in age or when predicting a specific individual's TBF or PBF.