Testing theories of dietary behavior change in youth using the Mediating Variable Model with intervention programs

Objective: To review and critique current experimentally-based evidence of theoretical mechanisms of dietary behavior change in youth and provide recommendations on ways to enhance theory evaluation. Methods: Interventions that examined mediators of dietary behavior change in youth (age 5-18 years) were identified via electronic database searches and reference scanning. Selected studies were reviewed for quality and content and findings were tabulated. Results: Seven published interventions were found. All were school-based but differed substantially in dietary outcome, target population, measures, methods of mediation analyses, and theoretical framework. Interventions were relatively unsuccessful in changing mediators. Self-efficacy and outcome expectations were the mechanisms most consistently associated with dietary behavior change. However, only outcome expectancies were identified as mediators in multiple interventions. Conclusions and implications: Few interventions have assessed the validity of theoretical mechanisms of dietary behavior change in youth. The variability in the design and target populations across studies makes it impossible to draw conclusions regarding the validity of theories and mediators of dietary behavior change in youth. Future intervention trials need to focus on the identification of effective procedures for mediator change and adopt a more rigorous and systematic approach to theory testing. This is likely to result in more effective interventions.