Age and gender differences in body composition in young adolescents

At the age of 11-15 (the period of younger adolescents), there are significant changes in body composition due to pre-pubertal and pubertal development. In our paper, the differences in indicators of body composition of elementary school students in the context of age and gender were evaluated. Boys and girls from primary schools aged 10-11 years (n=32 and n=38), 12-13 years (n=36 and n=57) and 14-15 years (n= 38 and n=33) were examined. In addition to age, body height (BH), body weight (BW), Quetelet's index (BMI), body fat mass (BFM), body fat mass index (BFMI), skeletal muscle mass (SMM), percentage of body fat (PBF), waist-hip ratio (WHR) and visceral fat (VFA) were monitored. The data were obtained using the InBody 230 device using the multi-frequency bioimpedance method of measuring body composition. The measured data were processed using IBM SPSS Statistics, version 20.0. Since data were not normally distributed (Shapiro-Wilk test), they were processed using non-parametric methods through Kruskal-Wallis Anova (age differences) and multiple comparisons with the Mann-Whitney U test with the application of the Bonferonni adjustment. The most significant differences were only found in the intersex comparison of 14-15-year-old pupils, when in the relative values of fat representation (BFMI and PBF), girls achieved higher mean values, on the contrary, higher values of in the group of boys are visible in the indicators describing active body mass (FFM, FFMI and SMM).