Associations of day-to-day eating pattern variability and eating jetlag with dietary and lifestyle insulin resistance indices in Iranian women: a cross-sectional study

Irregular eating patterns, including day-to-day variability and meal timing differences, may be associated with metabolic risk. However, little is known about their associations with dietary and lifestyle insulin resistance indices (DIR and LIR). This study examined these associations among Iranian women. In this cross-sectional study, 626 participants aged 20–60 years completed three non-consecutive 24-hour dietary recalls. Day-to-day variability, expressed as the standard deviation, was calculated for total energy intake, energy intake after 4:00 and 6:00 p.m., and the number of eating occasions. Eating jetlag was calculated as the absolute difference in eating midpoint between workdays and free days, with eating midpoint defined as the midpoint between the first and last eating occasions. Anthropometric measurements and blood samples were collected. DIR showed moderate positive correlations with insulin ( r = 0.36) and TG/HDL-C ratio ( r = 0.34), while corresponding correlations for LIR were weaker ( r = 0.19 and r = 0.21, respectively; P < 0.05). Greater variability in daily energy intake was associated with higher DIR [β = 81.74 (95% CI: 32.20, 131.29)] and LIR [β = 52.10 (0.69, 103.20)]. Higher energy intake after 6:00 p.m. and greater eating jetlag were associated with higher DIR and LIR, whereas higher energy intake after 4:00 p.m. was associated only with LIR. Age and chronotype modified associations with LIR. Greater energy intake variability, late-day intake, and eating jetlag were associated with higher DIR and LIR, with stronger associations in older women and varied by chronotype, highlighting the potential relevance of eating regularity and timing to dietary and lifestyle factors associated with insulin resistance indices.