Obesity is a chronic disease that is increasing in prevalence and that poses a serious risk for the hypertension, osteoporosis, heart disease, diabetes mellitus and certains forms of cancer. This study was performed to develop of obesity animal model and to assess the pharmacological assay for the rats of 8 weeks or 4 days after ovariectomization treated with estradiol for 8 weeks on the body weight. fat weight and food intake. The body weight, fat weight and food intake increased in the ovriectomized rats. In the rat of 8 weeks after ovariectomization treated with estradiol (250 mg/100 g) 8 weeks, the body weight decreased significantly (p<0.05). In the rats of 4 days after ovariectomization treated with estradiol 8 weeks, the body weight decreased significantly (p<0.05). These results suggest that estrogen plays a role in regulation body weight response to food intake and fat weight.