Predicting fast food avoidance behavior among male adolescents: a structural equation modeling approach to the theory of planned behavior

BACKGROUND: Fast food consumption is a growing public health concern, particularly among adolescents, due to its association with obesity and chronic diseases. Understanding the behavioral determinants of fast-food avoidance can inform the design of effective interventions targeting male adolescents. OBJECTIVE: This study aimed to investigate the determinants of fast-food avoidance behaviors among male high school students in Shiraz, Iran, using the Theory of Planned Behavior (TPB) and Structural Equation Modeling (SEM). METHODS: A cross-sectional study was conducted among 862 male students in grades 1 and 2 of high school in Shiraz in 2025. A multi-stage sampling strategy was applied, whereby 16 high schools were randomly selected from four educational districts. Within selected schools, classes and students were recruited using a convenience-based approach, and all eligible students present in the selected classes were invited to participate. Data were collected using a demographic questionnaire and a validated TPB-based instrument assessing knowledge, attitude, subjective norms, perceived behavioral control (PBC), behavioral intention, and fast-food avoidance behavior. Data analysis was performed using JAMOVI (v2.5.6), and SEM was employed to test the hypothesized TPB model. RESULTS: The final TPB model demonstrated excellent fit indices (χ²/df = 2.04, CFI = 0.94, RMSEA = 0.05). Attitude (β = 0.58), subjective norms (β = 0.34), and PBC (β = 0.26) significantly predicted behavioral intention (p < .001), which in turn strongly predicted fast-food avoidance behavior (β = 0.49, p < .001). PBC also had a direct effect on behavior (β = 0.31). Knowledge exerted an indirect effect on behavior through attitude and intention. Demographic variables, including parental education, household income, and maternal employment, were associated with TPB constructs. CONCLUSION: Fast-food avoidance behaviors among male adolescents are primarily influenced by motivational and control beliefs. From a practical and policy perspective, school-based nutrition education programs and adolescent health policies should prioritize strengthening positive attitudes, enhancing perceived behavioral control, and reinforcing supportive social norms to promote healthier dietary behaviors and reduce fast-food consumption among adolescents.