Abstract: The present invention relates to a method for treating liver steatosis or non-alcoholic fatty liver by using a 2-monoacylglycerol degrading enzyme. More particularly, the present invention provides a method for treating metabolic syndrome such as liver steatosis, non-alcoholic fatty liver, hyperlipidemia, type 2 diabetes, and/or obesity by using a 2-monoacylglycerol degrading enzyme, in which the 2-monoacylglycerol degrading enzyme completely degrades triglyceride into fatty acids and glycerol in a digestive tract such that fat absorption is delayed and blood absorption of triglyceride is decreased, and in which, in a case where monoacylglycerol is degraded by a monoacylglycerol lipase in a digestive tract, although degraded products of the monoacylglycerol are absorbed into digestive epithelial cells, recombination thereof into triglyceride in the digestive epithelial cells is delayed or energy consumption is promoted during this process.