Mineral-induced alkaline-reduced water (MRW) is generated by the chemical reaction of water with alkaline earth metals and characterized by high pH and low oxidation-reduction potential. As ROS are believed to have a role in the pathogenesis of obesity, we attempted to determine the effect of MRW on obesity in Sprague-Dawley (SD) rats fed on a high-fat diet. The body weight of the MRW group was significantly lower than that of the control group in most periods of the examination (P<0.05). Serum level of triglycerides (p<0.05) and fat deposition in the livers of the MRW group were found to have been significantly reduced. This suggests that MRW down-regulates lipid metabolism, thereby suppressing obesity. Possible mechanisms of MRW related to reactive oxygen species were also discussed. Our results suggest that MRW is effective in the alleviation of obesity in SD rats fed on high-fat diet.