The present invention relates to collagen hydrolysate as an active substance for treating sarcopenia, as an active substance against the degenerative loss of muscle mass and for improving muscle power, as an active substance for reducing the age-related loss of muscle mass, and as an active substance for stimulating the conversion of body fat mass to muscle mass. The invention further relates to a method for treating sarcopenia, comprising the repeated oral administration of collagen hydrolysate to a patient.