The present invention provides a method for preventing or ameliorating obesity, for inhibiting accumulation of visceral fat, for inhibiting accumulation of liver lipid, for preventing or ameliorating fatty liver, including using a material for a pharmaceutical product or food, which has inhibitory actions on body weight increase, accumulation of visceral fat and accumulation of liver lipid. The present invention is also directed to a method for preventing or ameliorating obesity, a method for inhibiting accumulation of visceral fat, a method for inhibiting accumulation of liver lipid, and a method for preventing or ameliorating fatty liver, which methods include administering potassium alginate to a subject in need thereof or having the subject take potassium alginate.
