[Problem] The purpose of the present invention is to provide a muscle-enhancing agent. The purpose of the present invention is also to provide food having a muscle-enhancing effect. [Solution] The inventors focused on the effects that Walleye fish protein has on physiological function, and as a result of repeated research, it was discovered that Walleye fish protein has a muscle-enhancing effect, which led to the present invention. Specifically, the present invention provides a fast muscle-specific muscle-enhancing agent containing fish protein of fish belonging to Gadiformes, and a muscle-enhancing agent that changes slow muscle to fast muscle. The present invention also provides food containing fish protein of fish belonging to Gadiformes.
