The invention provides methods of preventing or treating insulin resistance in a mammalian subject. The methods comprise administering to the subject an effective amount of an aromatic-cationic peptide having at least one net positive charge; a minimum of four amino acids; a maximum of about twenty amino acids; a relationship between the minimum number of net positive charges (pm) and the total number of amino acid residues (r) wherein 3pm is the largest number that is less than or equal to r+1; and a relationship between the minimum number of aromatic groups (a) and the total number of net positive charges (pt) wherein 2a is the largest number that is less than or equal to pt+1, except that when a is 1, pt may also be 1.