PROBLEM TO BE SOLVED: To provide, as novel uses of Euglena extract, novel adipocyte differentiation inhibitors, PPARγ expression inhibitors, C/EBPα expression inhibitors, adipocyte differentiation inhibitory food compositions, and adipocyte differentiation inhibitory cosmetic compositions.SOLUTION: The present invention provides novel adipocyte differentiation inhibitors, PPARγ expression inhibitors, C/EBPα expression inhibitors, adipocyte differentiation inhibitory food compositions, and adipocyte differentiation inhibitory cosmetic compositions, containing Euglena aqueous solvent extract as an active ingredient. The Euglena aqueous solvent extract is, for example, Euglena water extract or hot water extract.SELECTED DRAWING: Figure 3【課題】ユーグレナ抽出物の新規な利用方法となる新規な脂肪細胞分化抑制剤、PPARγ発現抑制剤、C/EBPα発現抑制剤、脂肪細胞分化抑制用食品組成物、及び脂肪細胞分化抑制用化粧料組成物を提供する。【解決手段】ユーグレナ水性溶媒抽出物を有効成分として含有する新規な脂肪細胞分化抑制剤、PPARγ発現抑制剤、C/EBPα発現抑制剤、脂肪細胞分化抑制用食品組成物、及び脂肪細胞分化抑制用化粧料組成物である。例えば、ユーグレナ水性溶媒抽出物は、ユーグレナの水抽出物又は熱水抽出物である。【選択図】図3