Effects of aqueous mulberry leaf extract (Morus alba L.) on glucose and lipid metabolisms in highfat and high-sucrose diet-induced overweight animal models were examined. Supplementation of mulberry leaf extract (MLE) resulted in body weight changes in both high-fat- and high-sucroseinduced overweight rats. Plasma insulin and Homeostasis model assessment-insulin resistance also significantly decreased by MLE treatment (p<0.05). In addition, plasma free fatty acid level was also decreased by MLE supplementation in high-fat diet-induced overweight rat (p<0.05). MLE supplementation significantly (p<0.05) increased the expression of insulin receptor genes at the transcriptional level. MLE supplementation decreased plasma insulin concentrations increased by high-fat or high-sucrose diets and improved insulin sensitivity by increasing the expression level of insulin receptor in muscle and adipose tissue.