A method and composition for administering leptin to a subject. The invention includes suspending isolated native leptin-containing milk fat globules in a suitable medium for administering to a subject. The suspended milk fat globules may be administered orally as well as by intravenous, intramuscular, intraperitoneal, other enteral routes of administration, and other parenteral routes of administration. The invention includes a method for treating growth or maturational-related disorders in newborns as well as subjects having conditions that can be treated by the administration of leptin.