An object of the present invention is to provide a fat-soluble lipase inhibitor which can contribute to prevention or treatment of obesity due to excessive fat intake or diseases caused by obesity, can be added to fats and oils of all types, and can mildly inhibit hydrolysis by lipase. The present invention is a lipase inhibitor containing, as the active ingredient, at least one substance which is a fat-soluble substance selected from among SLS type triacylglycerols (i.e., symmetric triacylglycerols composed of S which represents a short-chain fatty acid having from 2 to 6 carbon atoms and L which represents a long-chain fatty acid having from 16 to 22 carbon atoms), LUU type and UUL type triacylglycerols (i.e., asymmetric triacylglycerols composed of L which represents a long-chain saturated fatty acid having from 16 to 22 carbon atoms and U which represents an unsaturated fatty acid having from 16 to 22 carbon atoms) and glyceryl ether lipids wherein a long-chain alkyl or alkenyl chain is attached to the 1- or 3-position of the glycerin via an ether bond.