The present invention relates to a muscular strength enhancing agent produced from fruits, and provides a strength enhancing agent or a body-fat regulating agent, derived from natural products, that may enhance muscle strength, decrease body fat or suppress body-fat accumulation without decreasing the amount of skeletal muscle or the weight of viscus; more specifically, a polyphenol produced from fruits is used to provide muscular strength enhancing agents or body-fat regulating agents, foods/beverages and pharmaceuticals that may enhance muscular strength, decrease body fat or suppress body-fat accumulation. Strength enhancing agents or body-fat regulating agents effective to enhance muscular strength, of which active component being a polyphenol derived from fruits, and foods/beverages and pharmaceuticals containing them.