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

Aims: To examine whether adherence to dietary behaviors (DBA) and portion recommendations (DPA) after medical nutrition therapy (MNT) is associated with improved metabolic outcomes in individuals with diabetes. Methods: This cross-sectional study enrolled 1,002 adults with diabetes from 40 Diabetes Health Promotion Institutions (DHIP) in Taiwan. Registered dietitians assessed DBA and DPA, which were combined into a total dietary quality score (TDQS). Participants were categorized into tertiles: G1 (≤106.6), G2 (106.7–119.0), and G3 (≥119.1). Associations with metabolic outcomes were analyzed using correlation, ANOVA, logistic, and multiple linear regressions. Results: G3 participants had longer diabetes duration, lower BMI, waist circumference (WC), and abdominal obesity. They consumed fewer whole grains and oils, but more vegetables. The proportion achieving ABC targets was significantly higher in G3 than in G2 and G1 (15.9% vs. 14.7% vs. 14.4%), with the most notable difference observed in HbA1c target attainment. Each 1-point increase in the TDQS was associated with reductions in waist circumference (−0.119 cm), BMI (−0.044 kg/m²), HbA1c (−0.012%), and triglyceride levels (−0.883 mg/dL). Conclusions: Higher dietary adherence was associated with better metabolic outcomes and ABC goal achievement.