Both C3H-Ldlr-/- and C3H-Apoe-/- males fed the Western diet developed moderate obesity as evidenced by substantial increases in body weight when compared to age-matched chow-fed mice (33.2 ± 0.8 vs. 24.1 ± 1.0 g for C3H-Ldlr-/- mice, 35.0 ± 0.8 vs. 26.2 ± 1.2 g for C3H-Apoe-/- mice). The gene discussed is APOE; the disease is obesity disorder.