Sexual dimorphism from birth to age 60 in relation to the type of body shape

Sexual dimorphism depends on age. It can be analysed within a population by a comparison of sex-specific body measurements based on cross-sectional samples. We analysed four length measurements, three circumferences, and one skinfold diameter of a representative cross-sectional sample of healthy German subjects aged 0 to 65 years. We here report that sexual dimorphism of these body measurements already is present in newborns. The percentages of anthropometric differences between female and male subjects behave in a specific pattern during growth age from birth up to adolescence. Girls are born smaller on an average, but they have a more accelerated growth than boys. Girls reach the peak of their adolescent growth spurt earlier in their chronological age. This means that their biological age at this time is at least 2 years older than that of boys of the same chronological age. This sex-specifically differential onset of the adolescent growth spurt, and its peak, as well as the differential decrease of growth velocity cause a dramatic change in sexual dimorphism. This change is clearly shown in this cross-sectional study. Except for the subcutaneous fat layer, there is a clear male growth advantage in all of the measurements investigated after the peak of the adolescent growth spurt. The largest differences between the measurements of both sexes in favour of the male sex are reached at young adult age. In the further course of life, the anthropometrical differences between the sexes decrease again. Sexual dimorphism within a population at a defined chronological age is therefore not only the result of a developing sex-specific physique, but also the result of a sex-specific growth velocity during the successive stages of biological development. Interestingly, we found that the sex-specific velocity of physical development, and by this the development of sexual dimorphism, proceeds differently in the tall and slim leptomorphic individuals in comparison to the smaller and more corpulent pyknomorphic individuals.