Disclosed is a lipid metabolism-improving agent which has an excellent lipid metabolism-improving effect and is effective for the prevention and treatment of hyperlipemia, obesity and other diseases. Also disclosed is a lipid metabolism-improving product such as a food, a beverage, a nutrient composition and a feed, which contains the lipid metabolism-improving agent.The lipid metabolism-improving agent is characterized by comprising a whey protein hydrolysate as an active ingredient, wherein the whey protein hydrolysate is characterized by having a molecular weight distribution of 10 kDa or smaller wherein the main peak appears within the range from 200 Da to 3 kDa, and also having an APL (an average peptide chain length) of 2 to 8, a free amino acid content of 20% or less, and antigenicity of 1/10,000th or less of that of β-lactoglobulin.
