The present disclosure relates to methods for treating hair fibers, wherein the hair fibers are not fixed with an oxidizing composition, comprising the following steps:applying to the hair fibers at least one reducing composition containing no ceramide, comprising at least one reducing agent chosen from thiols and at least one cosmetic active agent chosen from polymeric active agents;increasing the temperature of the hair fibers with a heating iron at a temperature of at least 60° C., wherein the temperature of the hair fibers may be increased before or after optionally rinsing the hair fibers.