Allometric Scaling of Body Composition Components to Predict Bone Mineral Density (BMD) in Female Adolescents

Abstract

PURPOSE: Determine the best body-composition variable for predicting bone mineral density (BMD) by comparing standard, index-based, and allometricallyscaled components. Allometric scaling has been used when comparing metabolic changes of individuals of different size, gender, and age (Loftin, et al, 2001; Welsman & Armstrong., 2000; Janz, et al., 1998). The body composition components investigated included body weight (WGT), lean tissue (LT), body fat (BF), body mass index (BMI), lean tissue index (LTI = LT/Height2), body fat index (BFI = BF/Height2), (WGT.67), (LT.67), (LTI.67), (BMI.67), and (BFI.67). METHODS: Subjects: Sixty-two female adolescents (Mean Age + SD = 12.57 + 1.15 yrs). METHODS: Calculated BMD using DXA and measured height and body weight. RESULTS: Pearson Product Moment correlations indicated the allometrically-scaled body composition component, (LT.67), was the variable most highly associated with BMD (r =.770). Partial correlations controlled for age (in months) indicated the allometrically-scaled body composition component, (LT.67), was the variable most highly associated with BMD (ρ =.715). Simple linear regression indicated (LT.67) was the predictor variable with the best fit. Prediction of the dependent criterion variable, BMD, was calculated using the independent predictor variable, (LT.67). A significant regression equation was found. The subjects' BMD was found to be equal to.925(LT.67) - (.359), [F(1, 60) = 87.208, p < 05, SEE =.0667] with an R2 =.592. CONCLUSION: The allometrically-scaled body composition component, (LT.67), was the body composition variable most highly associated with BMD (r =.770), and it was also the best body-composition component of the eleven variables investigated to predict BMD. Further research in this area is recommended.