A lipase inhibitor; a dipeptide-containing food or beverage; a use of said inhibitor for inhibiting lipase; and a method for inhibiting lipase. It was discovered that a specific cyclic or straight-chain dipeptide or salt thereof exhibits a lipase inhibitory effect. The present invention provides an effective new means that contributes to the prevention or improvement of obesity or various diseases such as diabetes, hyperlipidemia, hypertension, or arteriosclerosis, said diseases being caused by obesity.