Changes in body composition during growth in healthy school-age children.

Bone-mineral-free lean body mass (LBM) and fat mass (FM) were determined by DXA scanning in 343 healthy children and adolescents (142 males) aged 4.9-19.3 yr. The main sex difference was the earlier flattening of the LBM according to age curve for girls compared to boys and the higher increase in FM with age in girls. 332 persons (140 males) were examined again after 1 yr and accretion rates for LBM and FM were calculated. The main sex difference was a later and higher peak in LBM accretion in boys compared to girls and a nearly constant increase in FM throughout puberty in girls, while boys had no increase in FM during puberty. The differences may reflect the higher androgen production in male puberty.