This invention is directed to methods of treating insulin resistance in a mammal which comprise administering an effective amount of a compound of formula I, where the variables are defined in the specification, or the stereoisomeric mixtures, diastereomerically enriched, diastereomerically pure, enantiomerically enriched or enantiomerically pure isomers, or the pharmaceutically acceptable salts and prodrugs thereof to said mammal. The compounds of formula I are growth hormone secretagogues and as such are useful for increasing the level of endogenous growth hormone. In another aspect this invention provides certain intermediates which are useful in the synthesis of the foregoing compounds and certain processes useful for the synthesis of said intermediates and th compounds of formula I. This invention is further directed to methods comprising administering to a human or other animal a combination of a functional somatostatin antagonist such as an alpha-2 adrenergic agonist and a compound of formula I.