Body composition in a population of school adolescents: a comparison of simple anthropometric methods and bioelectrical impedance.

OBJECTIVES: To report the anthropometric characteristics and body composition and to analyze the potential sex-based differences in Spanish schoolchildren and adolescents living in Granada and Ceuta. To estimate body fat percentage using regression equations and bioelectrical impedance to check for sex differences. An additional objective was to see whether the body fat percentages obtained by these two methods were similar.

METHODS: A cross-sectional study including 1,518 children and adolescents (aged 9-16) from 12 primary and secondary schools in Ceuta and Granada. The nutritional status of the subjects was assessed and their body fat percentage was calculated.

RESULTS: There was a strong sexual dimorphism, with higher prevalence rates of overweight in boys and obesity in girls. Girls had higher mean body fat levels regardless of the measuring method used (p<.001). Correlation between bioelectrical impedance analysis and regression equations was high (r=0.830), as was the internal correlation coefficient (ICC>0.75). A Bland-Altman comparison showed a high agreement between bioelectrical impedance and Behnke and Lohman equations.

CONCLUSIONS: Specific equations considering subject sex and age should be used to estimate body density. Regardless of the method used, girls had higher body fat percentages. The Behnke and Lohman equations, combined with BIA, were found to be the most accurate methods for measuring body density in the study population.