Methods for treating cancer are disclosed which comprise administering to a subject T cells which have been pretreated ex vivo or in vitro with a fatty acid catabolism promoter to condition the T cell to use fatty acids rather than glucose for energy production. Still other methods comprise co-administering to a subject having a cancer characterized by a solid tumor (a) an immunotherapeutic composition targeting an antigen or ligand on the tumor cell; and (b) a compound or reagent that promotes the use of fatty acid catabolism by tumor antigen-specific T cells in the tumor microenvironment and/or T cells pretreated ex vivo with the fatty acid catabolism promoter to condition the T cell to use fatty acids rather than glucose for energy production for adoptive cell transfer. Both methods may also employ co-administration of a checkpoint inhibitor.