The object of the present invention is to provide PPAR (peroxisome proliferator-activated receptor) activity regulators, which can be widely used for improving insulin resistance and preventing/treating various diseases such as diabetes, metabolic syndromes, hyperlipemia, high-blood pressure, vascular disorders, inflammation, hepatitis, fatty liver, liver fibrosis, NASH (non-alcoholic steatohepatitis) and obesity.The present invention provides PPAR activity regulators which comprise an acylamide compound having the specific structure, prodrugs thereof, or pharmaceutically acceptable salts thereof.