Disclosed are a method for activating lipid metabolism in the small intestine epithelium and also a method for promoting accumulation of fatty acids into the small intestine epithelium, each of which features administering an effective amount of a diacylglycerol. Also disclosed are methods for improving various symptoms in diabetes, which have ingesting a diacylglycerol. Ingestion of the diacylglycerol leads to accumulation of the fatty acids in the small intestine. The fatty acids so accumulated promote induction of .beta.-oxidation, thereby not only activating lipid catabolism but also making it difficult to allow lipids to accumulate as triacylglycerols. This series of actions eventually results in development of lowering action for blood remnant-like lipoprotein level and also lowering action for blood leptin level, and hence, lipid metabolism is improved. Further, energy consumption is enhanced by promoting the induction of .beta.-oxidation and activating lipid catabolism.