Development of a questionnaire for assessing the impact of children's food marketing exposure on diet-related outcomes.

Introduction: The Government of Thailand has drafted legislation to protect children from the harmful impact of unhealthy food (including beverages) marketing. Local evidence on Thai children's exposure to, and the impact of, this marketing is necessary to, first, support the adoption of this Law and, second, to contribute to assessing policy implementation and effectiveness. This study aimed to develop and validate a questionnaire for examining Thai children's exposure to unhealthy food marketing and its impact on diet-related outcomes. Materials and methods: To design the questionnaire, we first conceptualised the range of impacts of unhealthy food marketing on children's diet-related outcomes based on published frameworks. These outcomes related to food brand loyalty, preference, purchase and consumption. We conducted a literature review to gather related questions used in earlier surveys to assess these outcomes. Using these questions, we assessed content validity with five experts. Face validity and reliability were assessed for 32 children. Validity was assessed using Content Validity Index (CVI) and Kappa statistics. Reliability was assessed using Cronbach's alpha and intraclass correlation coefficients (ICC). Results: We identified 15 survey questions that had been used to assess the outcomes of interest. The CVI of all questions was 1.0, indicating perfect agreement with each question's relevance by the experts. Most questions were perceived to be easy to read and comprehend, suggesting face validity. Cronbach's alpha and ICC of all questions were both 0.75, demonstrating internal consistency across responses to questions about, separately, brand loyalty, preferences, purchase and consumption. Conclusion: The final 15-item questionnaire provides a valid and reliable survey instrument for measuring the impact of unhealthy food marketing on children's diet-related outcomes. This instrument will be useful for gathering local evidence on the need for policy reform to protect children from unhealthy food marketing in Thailand. The instrument also provides a cost-effective approach for generating evidence in other jurisdictions to propel policy actions. This is a pilot study and the validity and reliability needs further testing after a larger-scale roll-out.