Objective: To identify the effects of GnRH agonist therapy on body composition (lean and fat mass components) and body fat distribution. Methods: Fifteen women with uterine leiomyomas were given a GnRH agonist (leuprorelin acetate, 3.75 mg) monthly for 4 months. Weight, height, and body mass index (BMI, weight/height2) were recorded. Regional and total body composition, trunk-leg fat ratio, bone mineral density of the lumbar spine (L2–L4), and total body were assessed by whole-body scanning with dual-energy x-ray absorptiometry before and after treatment. Uterine volume was measured by transabdominal ultrasonography. Results: The mean (± standard deviation [SD]) lean mass of total body, trunk, and leg decreased significantly (36.3 ± 4.9 to 35.4 ± 4.4 kg, P < .01; 18.8 ± 2.8 to 18.1 ± 2.8 kg, P < .05; and 11.4 ± 1.8 to 11.1 ± 1.6 kg, P < .05; respectively), whereas body fat mass, percentage of body fat, and trunk fat mass increased significantly (20.8 ± 4.8 to 21.8 ± 4.6 kg, P < .01; 34.9 ± 5.9 to 36.5 ± 5.2%, P < .01; and 8.6 ± 3.0 to 9.3 ± 3.0 kg, P < .01; respectively). Trunk-leg fat ratio increased significantly (1.03 ± 0.32 to 1.12 ± 0.33, P < .05). Weight, BMI, arm tissue composition (lean and fat mass components), and leg fat mass did not change during 4 months of GnRH agonist therapy. Bone mineral density and uterine volume decreased significantly. Conclusion: Hypogonadism by GnRH agonist therapy induces lean mass loss, increased adiposity overall, and upper body fat accumulation.