Different chain lengths diacylglycerols (DAG) (long- and medium-chain) were synthesized from peanut and coconut oils. The effects of DAG with different chain lengths on body fat, blood lipids, and lipid metabolism-related enzymes in the liver and adipose tissue of C57BL/6J mice were investigated. Compared to peanut and coconut oils containing triacylglycerol (TAG), DAG-rich oils can significantly reduce the body weight, kidney weight, serum triglyceride (TG) content, hepatic fatty acid synthase (FAS), and Acetyl-CoA carboxylase (ACC) enzyme levels (p < 0.05) in C57BL/6J mice. Therefore, the effect of coconut oil DAG on improving body fat metabolism was probably due to the impact of DAG. Meanwhile, the body weight and serum TG content in coconut oil DAG group were lower than those in peanut oil DAG group. In addition, the spleen weight, hepatic ACC, and lipoprotein lipase (LPL) enzymes in coconut oil DAG group (0.07 ± 0.01 g, 2.08 ± 0.42 ng/mg pro, and 18.44 ± 5.23 ng/mg pro, respectively) were significantly lower than those in peanut oil DAG group. Although coconut oil DAG and peanut oil DAG have different fatty acid compositions, their effects on lipid metabolism showed no significant changes. Coconut oil DAG (peanut oil DAG) showed the improved lipid metabolism than that of coconut oil (peanut oil), which was probably due to the effect of DAG. PRACTICAL APPLICATION: Peanut and coconut oils are common edible oils. The oil containing DAG synthesized decreased the body weight and lipid accumulation in mice. Coconut oil is rich in medium-chain fatty acids, while peanut oil mainly consists of long-chain fatty acids. Due to the different contents of fatty acids, the synthesized structural lipids have different effects on lipid metabolism. Medium-chain triglycerides were considered as agents to alleviate obesity.