Purpose: The purpose of this study is to determine how transtheoretical model (TTM) constructions change through nutrition education for fat intake modification among overweight and obese women living in Shazand city, Iran. Design/methodology/approach: A semi-experimental design with intervention and control groups (50 women in each group) was performed. TTM constructions for dietary fat intake were measured through a questionnaire in four phases: before the intervention, immediately, one month and six months after the intervention. Participants in two groups were classified into inactive and active subgroups, based on their determined stage of change. Then in the intervention group, each subgroup received a separate education program of five or eight sessions for the active and inactive subgroups, respectively. Findings: The intervention resulted in significant progress in participants' stage of change compared to the control group (p = 0.002). Also, it resulted in an increase in the self-efficacy and decisional balance scores in both of the intervention subgroups, with these effects being more pronounced in the inactive subgroup, and these significant differences, compared to the control group, remained in the third and fourth phases. The intervention also positively impacted the behavioral processes, but this effect was not so long-lasting and decreased after six months. Originality/value: The results indicated the intervention effectiveness and the necessity of planning educational interventions to change fat consumption behavior. This study provides further insight into effective and sustainable nutrition education strategies based on behavioral change stages rather than traditional approaches. These methods should be used to design group interventions to change individuals' health behavior in future works.