The present invention relates to a composition for preventing or treating diabetes, disbesity or diabetic complications, comprising an oxyntomodulin analog as an active ingredient. The invention also relates to a method for treating diabetes, diabesity or diabetic complications, comprising administering a pharmaceutically effective amount of an oxyntomodulin analog to a subject. The oxyntomodulin analog has a high ability to activate the GLP-1 receptor and the glucagon receptor, compared to native oxyntomodulin. The oxyntomodulin analog induces the expansion of beta-cells and increases insulin secretion, thereby reducing blood glucose levels that were increased due to a high-calorie and high-fat diet. The oxyntomodulin analog induces decreases in body weight and diet intake to improve insulin sensitivity and allow blood glucose levels, which are not controlled due to insulin resistance, to be maintained at normal levels. Thus, the oxyntomodulin analog can be effectively used to prevent or treat of diabetes and related diseases.
