Utilizing the COM‑B Model to Influence Low‑Glycemic Dietary Behavior in Urban Thai Adults with Prediabetes

Background: Type 2 diabetes mellitus is an escalating public health issue in rapidly urbanizing middle-income countries. In Thailand, working-age adults increasingly develop prediabetes due to sedentary lifestyles, high glycemic diets, and limited access to supportive food environments. Existing research on determinants of low glycemic dietary practices remains fragmented, with few studies applying an integrated behavioral framework. Objective: This study examined behavioral pathways influencing low GI dietary behavior among urban adults with prediabetes, guided by the capability–opportunity–motivation–behavior (COM-B) model. Design and Methodology: A cross-sectional analytical study was conducted among 450 adults clinically diagnosed with prediabetes in Bangkok. Data were collected using a COM-B based questionnaire for assessing psychological and physical capability, social and physical opportunity, and reflective and automatic motivation. Path analysis using maximum likelihood estimation in LISREL version 8.72 assessed model fit and structural relationships. Results: The model demonstrated excellent fit (χ² = .32, df = 1, p = .57; RMSEA = .000; CFI = 1.00; SRMR = .005). Psychological capability (β = .47), physical capability (β = .42), physical opportunity (β = .53), social opportunity (β = .15), automatic motivation (β = .27), and reflective motivation (β = .09) significantly predicted low GI dietary behavior, explaining 77% of the variance. Conclusion and Implications: Capability and opportunity were the strongest determinants of low GI dietary behavior. Interventions that enhance nutritional skills and strengthen supportive social and physical food environments may be more effective than motivation focused strategies for improving dietary practices among urban adults with prediabetes.