Materials and Methods: In this interventional-experimental study, a total of 308 second-grade male and female high school students were selected and randomly assigned into control and intervention groups (154 subjects in each group). The entry criteria included the age range of 13-15 years, informed consent, and voluntary participation in the study. The SCT-based interventions were employed for the students, families, and schools using the student-family-school (SFS) approach. Data were collected employing a 3-part questionnaire including demographic characteristics, SCT-based determinants of F and V consumption by adolescents, as well as the frequency of F and V consumption. Finally, the obtained data were analyzed by descriptive and analytical statistics using SPSS software.

Results: Based on the results, the application of the student, family, and school-based interventions significantly increased the scores related to the constructs of environment, knowledge, skills, outcome expectations, outcome expectancies, observational learning, reinforcement, and self-efficacy in the intervention group compared to the control group (P < 0.001). In addition, the average amount of F and V consumption prior to intervention was 3.7±1.40 and 2.98±1.38 in experimental and control groups, respectively. Further, the corresponding values were 3.39±1.56 and 2.83±1.53 in the intervention and control groups two months after the intervention while they found to be 3.27±1.31 and 3.04±1.11 six months after the intervention in the two groups, respectively, which showed a difference between the groups during 2 and 6 months after the intervention (P < 0.002, <0.106, respectively).

Conclusions: In general, the application of interventions based on SFS approach led to an increase in the scores of SCT structures and the amount of F and V consumption in students. Therefore, SCT-based interventions are recommended to be used at the level of schools, families, and students in order to enhance the consumption of F and V among the students.