The invention concerns the use of at least a fatty ester for preparing a composition designed to inhibit 5&alpha-reductase activity. Said use produces a remarkable inhibiting effect of 5&alpha-reductase thereby providing a novel response for treating dermatological pathologies and/or disorders related to congenital or acquired exaggeration of 5&alpha-reductase activity, in particular for treating prostatic hypertrophy, prostatic adenoma, acne, hyperseborrhea, alopecia and hirsutism. The invention also concerns cosmetic treatment methods, in particular for greasy skin, and the use of said fatty esters as additives in a food product for human and/or animal consumption.