Associations of Total Dietary Quality Score, Dietary Behavior Adherence, and Dietary Portion Adherence with Metabolic Factors Among People with Type 2 Diabetes Mellitus

<b>Aims:</b> To examine the association between the total dietary quality score (TDQS) and metabolic outcomes among adults with type 2 diabetes (T2DM) in Taiwan. <b>Methods:</b> This cross-sectional study enrolled 981 adults with T2DM from 40 diabetes health promotion institutions (DHIPs). Registered dietitians assessed dietary behavior adherence (DBA) and dietary portion adherence (DPA) using a validated dietary quality questionnaire, which were combined into a TDQS. Participants were categorized into tertiles: G1 (≤106.7), G2 (106.8-118.7), and G3 (≥118.8). Associations with metabolic outcomes were analyzed using ANOVA, logistic, and multiple linear regression. <b>Results</b>: Participants in the highest TDQS tertile (G3) had significantly lower BMI, waist circumference (WC), fasting blood glucose (FBG), HbA1c, total cholesterol, and triglyceride levels, and a higher proportion achieved HbA1c < 7%. Compared with lower tertiles, G3 participants consumed more vegetables and derived a greater proportion of total energy from protein, whereas participants with a lower TDQS reported higher total energy and fat intakes. Each 1-point increase in TDQS was independently associated with reductions in WC (-0.155 cm), BMI (-0.151 kg/m²), FBG (-0.106 mg/dL), HbA1c (-0.136%), total cholesterol (-0.076 mg/dL), and triglyceride levels (-0.148 mg/dL). <b>Conclusions</b>: Higher TDQS is significantly associated with improved metabolic outcomes in adults with T2DM, supporting its use as a practical, multidimensional tool for clinical nutrition assessment and personalized dietary intervention.