To obtain the subject improper having suppressing and reducing actions on accumulation of visceral fats and improving actions on fat distribution by making the improper include a specific thiazolidine or oxazolidine derivative as an active ingredient.

This improper comprises a compound represented by formula I [A1 is a (substituted)cycloalkyl, an aryl or a heterocyclic ring; X1 is a direct bond, O, S, etc.; S1 is a (substituted)alkylene chain; Y1 is a direct bond, O, S, etc.; C1 is a (substituted)bivalent aryl or a monocyclic unsaturated hydrocarbon; D is a (substituted)alkylene chain; E is a carboxylic acid, an equivalent or a heterocyclic ring represented by formula II (G is S or O)] {e.g. 5-[(7- benzyloxy-3-quinolyl)methyl]-2,4-thiazolidinedione} as an active ingredient. For example, the daily dose thereof is about 0.1-100mg in the case of a parenteral injection and about 1mg to 10.0g in the case of oral administration.