Gonadotropin-releasing hormone agonists (GnRHa) have been widely used for decades to treat patients with central precocious puberty (CPP). Several studies have investigated changes in body composition in patients with CPP following GnRHa treatment, but the results are inconsistent. The aim of this study was to investigate changes in body mass index (BMI) in children treated with GnRHa for 2 years. We also assessed whether BMI affects treatment outcomes. This study included 383 girls (214 girls with central precocious puberty and 169 girls who underwent early puberty) treated with depot leuprolide acetate monthly for at least 2 years. We analyzed changes in BMI standard deviation score (SDS). Furthermore, blood luteinizing hormone (LH) levels were determined 30 min after depot leuprolide acetate administration every 6 months to evaluate adequate suppression of the hypothalamic-pituitary-gonadal axis. Pretreatment mean BMI SDS values were 0.07 +/- 0.69, 1.29 +/- 0.16, and 1.95 +/- 0.32 in the normal weight, overweight, and obese subjects, respectively. Mean BMI SDS values after 2 years of treatment increased significantly only in normal weight children (0.07 +/- 0.69 vs. 0.25 +/- 0.73, P < 0.001). LH levels 30 min after leuprolide injection after 2 years of treatment were not different among normal weight, overweight, and obese subjects. Although the difference in BMI SDS was relatively small, it standard deviation score increased significantly after 2 years of treatment in normal weight girls with early pubertal development.