BACKGROUND: The aim of this study was to evaluate the effects of sibutramine on serum adiponenctin levels, body mass index, body composition and insulin resistance in obesity women. METHODS: Twenty-eight healthy, non-diabetic, obese(BMI >25kg/m2) women(mean age: 34.46+/-13.67years, BMI: 31.00+/-4.10kg/m2) were enrolled in this study, and designed as sibutramine 10mg, administered orally, once daily for 12 weeks period. We assessed body composition, and measured the level of serum adiponectin, TNF-alpha, insulin, C-peptide and various biochemical parameters. RESULTS: Twelve weeks of 10mg/day sibutramine treatment achieved significant decrease in BMI from 31.00+/-4.10 to 28.72+/-4.16kg/m2(P<0.01), total fat mass from 30.61+/-5.86 to 26.39+/-6.10kg(P<0.01), percent body fat mass from 37.75+/-3.75 to 34.99+/-4.30%(P<0.01). Abdominal subcutaneous and visceral adipose tissue area were reduced from 315.74+/-125.35 to 263.71+/-117.87cm2 and from 114.77+/-41.14 to 91.88+/-33.05cm2(P<0.01). Cross-sectional area of low density muscle(LDM) at the mid thigh decreased from 17.22+/-7.45 to 11.58+/-5.90cm2(P<0.01). Insulin resistance(IR, as measured using the homeostasis model assessment of insulin resistance) decreased from 2.76+/-1.37 to 2.20+/-1.12(P<0.05). Serum adiponectin levels were increased from 5.34+/-1.27 to 6.37+/-1.67microgram/mL(P<0.01). Serum TNF-alpha levels were not statistically significant decreased(12.25+/-2.75 to 11.47+/-2.39pg/mL). CONCLUSION: In this study, the change of HOMAIR, adiponectin, free fatty acids, triglyceride and mid thigh low density muscle preceded weight loss. Therefore, the change of insulin resistance, fatty acids metabolism and energy homeostasis preceded weight loss. It is highly likely that this is in part caused by altered fatty acid metabolism, beta3-adrenoreceptors, or uncoupling protein. which is led by the increase in plasma adiponectin level.