Sexual dimorphism of body composition and insulin sensitivity across pubertal development in obese Caucasian subjects

Background Puberty is a period of rapid growth associated with metabolic, hormonal, and body composition changes that can influence risk factors for chronic diseases such as type 2 diabetes. Objective To evaluate body composition and insulin sensitivity (IS) modifications throughout puberty in a large group of obese Caucasian subjects. Methods Five hundred and nineteen obese subjects (4-19 years), grouped according to gender and Tanner stage (T), underwent oral glucose tolerance test. Quantitative insulin check index (QUICKI) and ISI were calculated as indexes of IS. In 309 subjects, body composition by dual-energy X-ray absorptiometry, IGF1, adiponectin, and leptin were also evaluated. Results Body composition modifications were sexually dimorphic, with girls not modifying fat and lean percentage and fat distribution (P>0.15), and boys decreasing fat percentage and increasing lean percentage and central fat depot (P<0.001) across Ts. IS decreased during mid-puberty and returned to prepubertal levels by the end of puberty. Girls showed lower IS than boys (P<0.01 and =0.03 for QUICKI and ISI respectively). In multivariate analysis factors that negatively influenced IS, independently from T or age, were total fat mass and central fat depot in girls (P<0.05 and <0.01, respectively), total fat and lean mass in boys (P<0.01). IGF1, adiponectin, and leptin were not related to pubertal IS. Conclusions In obese Caucasian subjects, further decrease of IS observed during puberty is a transient phenomenon. Factors that independently from T or age influence IS are central fat depot in girls, lean amount in boys, and total fat mass in both sexes.