Cross-sectional associations between meal timing patterns and diet quality indices in Iranian women.

Meal timing patterns (MTPs) are associated with energy and macronutrient intake, but their combined impact with food intake on overall diet quality remains underexplored. This cross-sectional study examined the relationship between MTPs and diet quality in a sample of 574 Iranian women aged 20-60 years from Tehran. Dietary intake was evaluated via three 24-hour dietary recalls, and demographic and anthropometric data were also collected. K-means cluster analysis on the basis of five dietary factors: morning and evening energy proportions, pre-sleep fasting, eating windows, and eating occasions were used. Diet quality was assessed via the Healthy Eating Index 2015 (HEI-2015), Carbohydrate Food Quality Score (CFQS-4), and Cholesterol-Saturated Fat Index (CSI). Three MTPs clusters were identified "pre-sleep fasting", "long-frequent", and "late-short". The HEI-2015 scores were lower for the "long-frequent" (fully adjusted: β = -2.85, 95% CI: -4.85 to -0.87) and "late-short" (-2.11, -4.12 to -0.23) patterns than for the "pre-sleep fasting" cluster. Only the "late-short" pattern was consistently associated with reduced CFQS-4 scores across all the models (-0.19, -0.32 to -0.07). No associations were detected between MTPs and CSI. Morning energy intake was positively associated with the HEI-2015 score (0.21, 0.12 to 0.30), whereas evening energy intake was inversely associated with the CFQS-4 score (-0.003, -0.09 to -0.001). Additionally, "pre-sleep fasting" was related to decreased CSI (-0.003, -0.001 to -0.00003). These findings suggest that long-frequent and late-short MTPs are linked to lower diet quality. Longitudinal studies are needed to confirm these results and their implications for health.