In one aspect, the invention provides a method of screening and, optionally, treatment of an individual suffering from an insulin resistance disorder by screening an individual in need of treatment for an insulin resistance disorder for one or more genetic variations indicating a predisposition to a response to an insulin sensitizer; and, optionally, administering or not administering an insulin sensitizer to the individual based on the results of the screening. The insulin sensitizer for which the individual is screened and the insulin sensitizer that is administered or not administered may be the same or different. In another aspect, the invention provides methods comprising identifying one or more genetic variations, e.g., one or more single nucleotide polymorphisms, that at least partly differentiate between a subset of a plurality of individuals who experience a response when administered an insulin sensitizer, and a subset of said plurality of individuals who do not experience a response when administered the insulin sensitizer. The invention also provides nucleic acids, polypeptides, antibodies, kits, and business methods associated with these screening and association methods.