Objective: To conduct an evaluation of an educational program based on the health promotion model (HPM) and stages of change to improve physical activity (PA) behavior among Iranian adolescents.

Methods: This was a group randomized controlled trial with 165 participants in two groups (intervention/control). Data were collected using self-reported questionnaires based upon HPM constructs (benefits and barriers of action, self-efficacy, activity-related affect, interpersonal influences, and situational influences). The stages of change scale was used to select eligible participants (were placed on precontemplation, contemplation, or preparation stages) and to assess the trend. After collecting baseline data, the intervention was administered to the participants and follow-up data was collected 3 months after intervention.

Results: In all, 88 males and 77 females with a mean age of 13.99±0.4 participated in the study. The differences in all HPM constructs, except activity-related affect and social influences, were significant (p < 0.01) between baseline and follow-up measurements. Adolescents in the intervention as compared to the control group were placed in action (70%) or preparation (30%) stages at follow-up. Multiple regression analysis revealed that competing preferences, social norms, role models, (p < 0.001), and commitment to action plan can significantly predict PA behavior. The model accounted for 22.5% of the variance in PA.

Conclusions: The results suggest that educational interventions based on stages of change can have important implications for improving PA among adolescents in more constructs of HPM.