The present invention provides an agent for preventing the increase in a body weight (or for decreasing a body weight) or an anti-obesity agent each comprising at least one component selected from the group consisting of EPA and pharmaceutically acceptable salts, esters and derivatives thereof as an active ingredient for obesity in which the increase in the formation of hepatic lipid or the occurrence of fatty liver is mild, preferably the increase in the formation of hepatic lipid or the occurrence of fatty liver is not observed.
