BACKGROUND: A healthy diet is essential for managing metabolic syndrome (MetS), but moderation and dietary adequacy remain ambiguous. METHODS: Data from the recruiting phase of the Shiraz University of Medical Sciences Employees Health Cohort Study (SUMS EHCS) were utilized to conduct this cross-sectional analysis. A validated 168-item semi-quantitative food frequency questionnaire (FFQ) was used to collect dietary data in the Persian cohort. In the current study, the healthy eating index (HEI-2015) includes two components, namely adequacy and moderation which were used to evaluate the quality of the diet. RESULTS: The study included 3380 health workers, with a mean age of 41.81±7 years and 55.2% female. Among them, 22.3% met the ATP III criteria for MetS. The mean total HEI, adequacy, and moderation scores were 63.89±9.53, 41.03±5.88, and 20.13±4.90, respectively. Adjusted model analysis showed no significant correlation between diet adequacy and MetS or its components, but found a significant association between diet moderation and MetS (OR: 1.03 [1.008-1.05]), abdominal obesity (OR: 1.02 [1.003-1.04]), elevated serum triglycerides (TGs) (OR: 1.02 [1-1.03]), and elevated fasting blood sugar (FBS) (OR: 1.03 [1.005-1.05]). CONCLUSION: This study found that there was a significant correlation between diet moderation and abdominal obesity, elevated serum TGs, elevated FBS, and MetS. Future studies on the topic are recommended.