Development and Psychometric Validation of a Knowledge, Attitudes, and Practices (KAP) Questionnaire on Sustainable Diets in Taiwan

<b>Background</b>: Sustainable dietary transitions are increasingly emphasized in public health policy; however, validated psychometric instruments assessing knowledge, attitudes, and practices (KAP) in Asian contexts remain limited. <b>Objectives</b>: This study aimed to develop and evaluate a KAP questionnaire on sustainable diets and examine sociodemographic variations and behavioral correlates among Taiwanese adults. <b>Methods</b>: A two-phase mixed-methods design was used, including expert validation and a cross-sectional online survey (<i>n</i> = 587). Construct validity was examined using exploratory factor analysis, and reliability was evaluated through internal consistency and test-retest assessments. Multivariable logistic regression models were fitted to identify factors associated with low adherence to a low-carbon diet. Model diagnostics included variance inflation factors (VIF), Hosmer-Lemeshow tests, Nagelkerke pseudo-R², and ROC analysis. <b>Results</b>: Content validity was high (S-CVI/Ave = 0.95-0.98). The attitude and practice domains demonstrated satisfactory internal consistency, whereas the knowledge domain showed comparatively lower reliability. In multivariable logistic regression analyses, higher attitude scores were independently associated with lower odds of low adherence to a low-carbon diet. Eating-out frequency and clear awareness of sustainability in Taiwan's Dietary Guidelines were also significantly associated with adherence. The fully adjusted model demonstrated adequate calibration and excellent discrimination (AUC = 0.778). <b>Conclusions</b>: The instrument provides preliminary psychometric evidence supporting the assessment of sustainable diet-related KAP among Taiwanese adults. Attitudes appear more strongly associated with dietary practices than knowledge alone. The questionnaire may support future monitoring and research.