Eating time variation from weekdays to weekends and its association with dietary intake and BMI in different chronotypes: Findings from National Health and Nutrition Examination Survey (NHANES) 2017-2018.

Evidence suggests that differences in meal timing between weekends and weekdays can disrupt the body's circadian rhythm, leading to a higher BMI. However, the relationship between this mealtime variability, BMI and dietary intake is little explored in scientific literature at population level and requires further investigation. This study aimed to investigate the associations between mealtime variation from weekdays to weekends (eating midpoint jetlag), dietary intake and anthropometric parameters (weight, waist circumference, hip circumference and BMI), based on individuals' chronotype. The study utilized data from NHANES 2017-2018. Usual food consumption was estimated by calculating the weighted average of participants' food intake on weekdays and weekends. Eating midpoint jetlag, defined as the absolute difference between the midpoint of the first and last mealtimes on weekends and weekdays, was calculated. Chronotype was assessed by participants' mid-sleep time on weekends, adjusted for sleep debt. Linear regression analysis was conducted to investigate the associations between variables. The sample was categorized into chronotype tertiles for further analysis. The first tertile indicates morningness tendency and the third tertile indicates evening tendency. The study did not find associations between eating midpoint jetlag and anthropometric parameters, calorie or nutrient intake. However, among individuals in the third chronotype tertile, there was a positive association between eating midpoint jetlag and BMI (β = 1.2; 95%CI 1.13, 1.27). Individuals in the first tertile showed a positive association between eating midpoint jetlag and calorie (β = 96.9; 95%CI 92.9, 101.7), carbohydrate (β = 11.96; 95%CI 11.2, 12.6), fat (β = 3.69; 95%CI 3.4, 3.8), cholesterol (β = 32.75; 95%CI 30.9, 34.6), and sugar (β = 8.84; 95%CI 8.3, 9.3) intake on weekends. Among individuals with an evening tendency, delaying meals on weekends appears to be linked to a higher BMI. Conversely, among individuals with a morning tendency, eating meals later on weekends is associated with higher caloric intake on weekends.