Disclosed is the use of a fat accumulation suppressor in the manufacture of a medicament for suppressing or preventing fat accumulation in a subject, wherein the fat accumulation suppressor comprises as an active ingredient a whey protein hydrolysate, wherein said hydrolysate has: (1) a molecular weight range of no higher than 10 kDa and a main peak of molecular weight at 200 Da to 3 kDa； (2) an APL (average peptide chain length) of 2 to 8； (3) a free amino acid content of 20% or lower； (4) a branched chain amino acid content of 20% or higher； and (5) an antigenicity of 1/100,000 or lower relative to beta-lactoglobulin.
