Objetives This experimental study is designed to investigate the effects of kwakhyangjungkisangamibang extract on the changes of adipose tissues, serum insulin and leptin levels in rats induced by a high fat diet. The leptin has been proposed to be involved in the role of food intake and energy expenditure. Methods During the 8 weeks of experimental period, male Sprague-Dawley rats were fed on the 2 different diets: the normal diet AIN-76A and high fat(beef tallow) diet ad libitum, of which 40% of the calories intake was fat. 9 rats in the control and high fat diet group were killed for the baseline experiment at 4 weeks of age. The high fat diet group was divided into three groups: control group, experimental group I(high fat diet plus kwakhyangjungkisangamibang extract), and experimental group II(high fat diet plus mahuang). The body weight, hypodermal fat tissue, serum lipid profile, insulin and leptin levels were measured after the administration of the high fat diet and extract. Results 1. The body weight was decreased in experimental group II, but there was not a significance difference compared to the control group. 2. The peritoneal, visceral, and hypodermal adipose tissue was decreased in experimental group I, but there was not a significance difference compared to the control group. 3. The lipid profile was decreased in experimental group I, but not in group II. 4. The insulin concentration was increased in experimental group I and II, but there was not a significance difference compared to the control group. 5. The leptin level was increased significantly in experimental group I(p<0.05) and II(p<0.01) compared to the control group. Conclusion The results of this study indicate that kwakhyangjungkisangamibang has an effect on the regulation of obesity.