Analyses of body composition charts among younger and older Chinese children and adolescents aged 5 to 18 years

BACKGROUND Childhood obesity has become a major public health problem in China. The objective of this study was to examine the effect of age and sex on the relationship between fat-free mass (FFM) and fat mass (FM), fat-free mass index (FFMI) and fat mass index (FMI) in Chinese children using body composition chart analysis, and to compare the changing pattern with Caucasian and Japanese counterparts. METHODS A total of 1458 children (790 boys and 668 girls) between 5 and 18 years of age were studied to determine a body composition by bioelectrical impedance analysis. The relationship of FFM and FM, FFMI and FMI were delineated by body composition charts. RESULTS Different changing patterns in body composition were observed during 5-11y (younger age group), and 12-18y (older age group), with non-significant sex difference with FM and FMI for the younger age group and significant sex and age differences for the older age group. For the younger age group, simultaneous increase of FFM and FM was found in both genders. However, for the older age group, the increase in weight and BMI with age is largely due to the increment of FFM and FFMI in boys, and of FM and FMI in girls. In addition, different changing patterns in body composition exist between Chinese children and their Caucasian and Japanese counterparts, largely due to the higher fat mass component in Chinese subjects. CONCLUSIONS Our results indicate that age- and gender-related changing patterns of body composition in Chinese children may differ at different growth stage, and differ with those in Caucasian and Japanese children at the same age period. Such changing patterns should be considered when designing the intervention proposal for childhood obesity in China.