To investigate whether dietary behaviors adherence (DBA) and dietary portion adherence (DPA) after medical nutrition therapy were associated with improved metabolic outcomes among individuals with diabetes.

This cross-sectional study enrolled 1,002 adults with diabetes from 40 Diabetes Health Promotion Institutions (DHPIs) in Taiwan. DBA and DPA were assessed by registered dietitians. A total dietary quality scores (TDQS), comprising DBA score and DPA scores, was calculated. Participants were categorized into tertiles based on TDQS: G1 (≤106.6), G2 (106.7–119.0), and G3 (≥119.1). Associations between dietary adherence and metabolic outcomes were evaluated using Pearson correlation, ANOVA, logistic regression, and multiple regressions.

Consumption of low-glycemic index and high-fiber foods was inversely associated with body mass index (BMI), waist circumference (WC), HbA1c, and triglycerides. Compared with G3, participants in G1 exhibited significantly higher BMI, WC, HbA1c levels, and an increased risk of abdominal obesity. G3 demonstrated higher intake of vegetables (3.6±1.4 servings/day) and dairy (0.6±0.6 servings/day). Participants in G1 had higher odds of abnormal body weight (OR 1.469, 95% CI 1.018–2.121), abdominal obesity (OR 2.211, 95% CI 1.492–3.277), elevated HbA1c (OR 1.493, 95% CI 1.069–2.086), and elevated triglycerides (OR 1.547, 95% CI 1.082–2.212). Each 1-point increase in TDQS was associated with reductions in WC (−0.119 cm), BMI (−0.044 kg/m²), HbA1c (−0.012%), and triglycerides (−0.883 mg/dL).

Greater adherence to dietary behavior and portion recommendations was associated with improved metabolic outcomes and higher likelihood of achieving ABC goals in individuals with diabetes.