BACKGROUND Depot preparations of gonadotropin-releasing hormone agonists (GnRHa) are the gold standard drugs for the treatment of central precocious puberty. A concern about these drugs is obesity. OBJECTIVE This study aimed to investigate the effect of gonadotropin-releasing hormone agonists (GnRHa) therapy on body mass index (BMI) in girls with central precocious puberty (CPP). METHODS The girls with onset of puberty before eight years of age or menarche before nine years of age were studied. The weight, height, BMI, and pubertal stage were determined before and at sixth and 12th months of treatment. The GnRHa (Triptorelin) was administered intramuscularly for patients with rapidly progressive forms of CPP. Patients with slowly progressive forms of CPP were considered as control group. RESULTS From 110 subjects with CPP, 46 girls (41.8%) were considered as intervention and 64 (58.2%) as control groups. The mean age at initial visit was 7.46 ± 1.03 years. The BMI standard deviation scores in both groups was not significantly different at sixth and 12th months of treatment compared with baseline (P = 0.257 and P = 0.839, respectively). The prevalence of obesity was not significantly different between study groups at baseline and at and sixth and 12th months of therapy (P = 0.11, P = 0.068, and P = 0.052, respectively). CONCLUSIONS The GnRHa therapy has no effect on BMI and the prevalence of obesity.