This paper aims to present a model of obesity and leanness based on eum, yang, ki and blood metabolism of Korean medicine. I analyzed the theory of eum, yang, ki and blood metabolism, yang transforming ki and eum forming the body on Korean medicine, and compared them with energy homeostasis by anabolism and catabolism of modern medicine. In the eum and yang theory, the metabolic process of the human body is dominated by synergism and antagonism between eum force and yang force. When the balance of eum and yang collapses, all the pathological actions of the human body appear, and in the eum and yang metabolic process, an imbalance between yang transforming ki and eum forming the body occurs. The function of yang transforming ki is reduced to ki deficiency, and the function of eum forming the body is increased to blood excess. When blood excess and ki deficiency is given, energy intake increases, energy expenditure decreases, overweight and obesity occur. On the contrary, the function of yang transforming ki is increased to ki excess, and the function of eum forming the body is decreased to blood deficiency. When ki excess and blood deficiency is done, energy intake decreases and energy expenditure increases, the body becomes leanness. When the balance of eum, yang, ki and blood metabolism collapses and becomes blood excess and ki deficiency, overweight and obesity occur, and when ki excess and blood deficiency is done, the body becomes leanness. The energy homeostasis of the human body can be explained by eum, yang, ki and blood metabolism of Korean medicine and it contains the concept of anabolism and catabolism of modern medicine.