The anti-obesity effects of fermented Castanea crenata inner shell extract (FCCE) were investigated using high-fat diet (HFD)-induced obese mice. In the FCCE intake groups, body weight gain and adipocyte area were significantly reduced, especially body weight gain in the 250 mg/kg FCCE group (G4) decreased by 37%, respectively, compared with negative control group (G2, HFD group). After oral administration of the FCCE, the increase of serum low-density lipoprotein (LDL)-cholesterol induced by HFD was suppressed significantly, as well as the level of aspartate aminotransferase, and alanine aminotransferase, which are markers of hepatitis induced by obesity. Serum leptin in G4 group was significantly decreased to less than that of G2 group. Also, in G4 and 500 mg/kg FCCE group (G5), enzymes-related lipogenesis, citrate synthase, and ATP citrate lyase were decreased, whereas the level of enoyl-CoA hydratase used for β-oxidation was significantly increased in comparison with normal diet group. Furthermore, the FCCE stimulated the expression of lipolytic regulators, especially AMP-activated protein kinase. In conclusion, we suggest that the FCCE may ameliorate in diet-induced obesity by regulating lipid metabolism.