Ontogenesis changes and sex dimorphism of subcutaneous fat distribution: 12-year longitudinal study of children and adolescents from Cracow, Poland.

The aim of the work was to analyze the direction and tempo of subcutaneous fat redistribution during ontogenesis, appearing sex differences and relations to puberty on the basis of 12-year longitudinal data of 270 boys and 154 girls from Cracow, Poland. They all had complete data (from 7 to 18-years old) of three trunk (subscapular, abdominal, suprailiac) and three extremity (triceps, knee, medial calf) skinfold thicknesses. The type of subcutaneous adipose tissue distribution was determined based on trunk to extremity ratio to analyze the process of fat redistribution. The analysis included medians of extremity and trunk skinfolds and medians of their sums and age altered frequency of central and peripheral type of fat distribution. To present empirical values, the median variability of the sums of three trunk and extremity skinfolds was calculated using a third degree polynomial as an age function. Polynomial regression of extremity skinfolds median explained 88% of its variability (F = 71.2, P < 0.001) and for trunk skinfolds as far as 96% (F = 111.65, P < 0.001). The median variability curves of both types of distribution crossed at the age of 11.88 in girls and 13.45 in boys directly preceding puberty stage, which indicated clear dependencies between fat redistribution and puberty. The results showed a tight connection between the process of subcutaneous fat redistribution and puberty, and also sex dimorphism of the process. More dynamic fat redistribution in boys contrasted trunk and extremity fatness, while in girls less dynamic changes resulted in more even fatness.