The relationship between obesity and body compositions with respect to the timing of puberty in Chongqing adolescents: a cross-sectional study

Background: It is well known that excess adiposity during childhood may influence pubertal development. However, the extent to which body compositions vary in throughout puberty in boys and girls is currently unknown. The aim of this study was to investigate whether obesity and body compositions correlate with the timing of puberty in boys and girls. Methods: By random cluster sampling, our study analyzed data from 1472 students (690 girls, 782 boys) aged 6-17 years from two schools in the Chongqing area. Data were collected by physical examination of weight, height, and skinfold thicknesses. Testicular volume was measured in boys and breast development in girls. By which we got the indicators of obesity, timing of puberty and body compositions. Probit regression analysis was used to group subjects into early puberty (> P-25), on-time puberty (P-25 similar to P-75), and delayed puberty (< P75). Chi-square test was applied to assess the distribution differences of fat levels among puberty groups by sex. Multivariate analysis of covariance was used to examine the association between timing of puberty and body composition indicators. Results: There were significant differences in the distribution of fat levels (normal weigh, overweight, obesity) among different pubertal groups in different sex (boys:X-2 = 10.639, P = 0.031; girls:X-2 = 63.232, P = 0.000). Multivariate analysis of covariance showed that percentage of body fat, fat mass and fat-free mass in the delayed puberty girls were significantly lower than the girls in the on-time puberty and early puberty, while body density had the opposite result (all P < 0.001). Body density, percentage of body fat, fat mass and fat-free mass of boys all had no significant difference among different timing of puberty groups (all P > 0.05). Conclusions: In girls, delayed puberty was negatively correlated with Obesity, percentage of body fat, fat mass and fatfree mass, and positively correlated with body density. But in boys, delayed puberty was only negatively correlated with Obesity, the relation between puberty and body compositions was not found.