Is Body Mass Index Related to Body Composition in Kindergarten and First Grade Students?

Abstract

Body Mass Index (BMI) is frequently used to estimate overweight and obesity. BMI is determined by dividing weight in kg by height in meters squared. The relationship between BMI and body composition has not been validated in young children. PURPOSE: To determine if BMI is related to selected measures of body composition in kindergarten and first grade students. METHODS: Thirty-seven (20 boys, 17 girls) kindergarten and first grade students (5–8 yrs. old) participated in the study. Informed consent and child assent were obtained. Height, weight, waist circumference (WC), sum of tricep and medial calf skinfolds (SF), two forms of bioelectrical impedance analysis (BIA), and BOD POD measurements were gathered on the participants. Means and standard deviations were calculated for all variables. Pearson product-moment correlations (? = 0.01) were obtained between BMI and each measure of body composition. BMI was compared individually to WC, SF, ohms readings from the Tanita TBF-150 and the Bioanalogics BIA, and body density measured from the BOD POD. RESULTS: Means and standard deviations for each measure were: height (121.5 ± 7.6 cm), weight (25.3 ± 7.1 kg), BMI (16.9 ± 3.3), WC (57.5 ± 7.5 cm), SF (22.6 ±11.2 mm), Tanita (629 ± 58 ohms), Bioanalogics (675 ± 66 ohms), and BOD POD (38.68 ± 0.02). Correlation coefficients for BMI and each measure were: WC (r = 0.95), SF (r = 0.93), Tanita (r = −0.62), Bianalogics (r = −0.48), and BOD POD (r = −0.67). All relationships were statistically significant at p ≤ 0.01. Positive correlations were found for BMI and WC and BMI and SF. Negative correlations were found between BMI and BIA and between BMI and BOD POD. CONCLUSION: BMI is related to all selected measures of body composition included in this study. The strongest relationships were between BMI and WC and between BMI and SF.