Dysregulation of the gut environment is thought to be a potential pathogenic mechanism of obesity, with a growing body of research suggesting that the gut environment can affect various metabolic organs leading to metabolic disease. Fiber fermentation by gut microbes produces short-chain fatty acids, including butyrate, which are absorbed from the intestines or excreted in the feces, and are known to improve the characteristics of obesity and diabetes. Thus, we investigated whether a butyrate-containing fermented product currently in development could improve metabolic disease in a high-fat diet-induced obesity/diabetic mouse model. We administered CR057-071 daily for two months, monitoring body weight and feed intake weekly, while examining factors associated with obesity/diabetes such as glucose, insulin, GLP-1, and HbA1C. As a result, in the group receiving CR057-081, weight gain induced by a high-fat diet was reduced, and factors related to obesity/diabetes showed improvement. Furthermore, histological analysis revealed an amelioration of non-alcoholic fatty liver disease in the group administered with CR057-071, along with a reduction in inflammatory markers in both the liver and blood induced by the high-fat diet. These findings suggest that the butyrate-containing fermented product being developed has the potential to ameliorate metabolic disorders by addressing not only the direct factors contributing to obesity/diabetes but also the associated inflammation.