PROBLEM TO BE SOLVED: To provide a neutral fat accumulation promoter and a breast-enlarging agent which each promotes neutral fat accumulation in local fat cells and is effective for accumulating and enlarging fat tissues.SOLUTION: The neutral fat accumulation promoter or the breast-enlarging agent contains, as an active ingredient, an extract obtained by extracting one or more shellfishes selected from among Tapes philippinarum, Meretrix lusoria, Neptunea arthritica, Fulvia mutica, Tresus keenae, Spisula sachalinensis, Patinopecten yessoensis, and Atrina pectinata japonica using carbon dioxide as a supercritical extractant.