Chronotype-specific associations of meal timing patterns with cardiometabolic health in women: a cross-sectional study.

Background: Although prior studies have examined meal timing and health, few have considered the impact of individual chronotypes and diurnal preference. This study explored how meal distribution and chronotype-morning (M-type) versus evening (E-type)- are associated with cardiometabolic health.

Methods: A cross-sectional study was conducted among 574 women in Tehran, Iran. Dietary intake was assessed through three 24-hour recalls and chronotype was determined via the Morningness-Eveningness Questionnaire. Cardiometabolic markers-including blood pressure (BP), glucose, lipids, insulin, and high-sensitivity C-reactive protein (hs-CRP)-were measured.

Results: In E-type individuals, higher breakfast energy intake was linearly associated with lower systolic [β 95% CI, -0.03 (-0.05 -0.01)] and diastolic BP [-0.01 (-0.04 -0.003)]. Afternoon energy intake was associated with lower BMI [-0.02 (-0.04 -0.001)] and hs-CRP [-0.001 (-0.002 -0.0006)] in E-type women. Additionally, U-shaped associations were found between breakfast intake and systolic BP (turning point: 23% of total energy intake (TEI)), and between afternoon intake and BMI (13% TEI) and hs-CRP (12% TEI). In contrast, higher dinner energy intake was linearly associated with greater BMI in the intermediate [-0.01 (-0.02 -0.002)] and E-type group [0.05 (0.003 0.09)], respectively. Eating window was associated with higher fasting blood glucose [0.001 (0.002 0.003)] in E-type vs. M-type individuals.

Conclusion: Aligning energy intake with wake-up time-rather than delaying meals-may benefit evening chronotypes prone to circadian misalignment. Moderate breakfast and afternoon intake, with lower dinner intake, was related to better cardiometabolic health. Accordingly, longitudinal studies are advocated.