The Timing of Macronutrient and Major Food Group Intake and Associations with Mortality Among US Adults, 1999-March 2020

ImportanceEating timing has been increasingly linked to human health, yet national trends in macronutrient/food group timing and their health implications remain unclear. ObjectiveTo characterize trends in timing of energy, macronutrient, and food group intake among US adults and examine their associations with mortality. DesignCross-sectional analysis of eating timing trends using National Health and Nutrition Examination Survey (NHANES, 1999-March 2020) data; longitudinal analysis of mortality through December 2019. SettingA nationally representative sample. ParticipantsAdults aged [≥]20 years with valid 24-hour dietary recall data. ExposuresTiming of energy, macronutrient, and food group intake across predefined 4-hour blocks: 2:00-5:59 am (predawn), 6:00-9:59 am (morning), 10:00 am-1:59 pm (noon), 2:00-5:59 pm (afternoon), 6:00-9:59 pm (evening), and 10:00 pm-1:59 am (midnight). Main Outcomes and MeasuresSecular trends in eating timing and mortality. ResultsAmong 50,264 adults (mean age, 47.5 years; 51.2% women), evening accounted for the largest proportion of daily energy intake (weighted mean proportions across years, 31.9%-33.3%), followed by noon (24.7%-26.8%), afternoon (19.9%-21.8%), morning (13.5%-14.9%), and overnight (midnight and predawn; 5.6%-6.5%), with 23.4%-28.0% of adults consuming foods at midnight; similar distribution patterns were observed for macronutrient and food intake, except whole grain intake peaked in the morning and fruit, egg, and dairy intake distributed more evenly. Over time, energy intake proportions declined at noon and midnight but increased in the afternoon; while the secular trends varied by macronutrients and food groups. On average, fasting started at 8:34-8:51 pm and ended at 8:41-8:52 am. Mean midpoint and duration for energy intake were 2:38-2:48 pm and 11.9-12.2 hours, respectively. Male, non-Hispanic Black, and socioeconomically disadvantaged groups had larger midnight intake proportions and later intake midpoints. Reallocating 5% of daily energy intake from other blocks to midnight was associated with higher cardiovascular mortality (HR, 1.09; 95% CI, 1.02-1.17), driven by carbohydrates and related foods; reallocating 5% to predawn was associated with higher cancer mortality (1.22; 1.05-1.41), driven by proteins and related foods. Each 1-hour delay in the start/end of fasting and intake midpoint was associated with an 8%-9% higher risk of cardiovascular mortality. Conclusion and RelevanceFrom 1999 to March 2020, US adults consistently consumed the highest energy, macronutrients, and most foods in the evening and started fasting relatively late, with a quarter of adults having midnight consumption. Higher overnight intake and delayed eating timing were associated with higher mortality, particularly for specific macronutrients and foods, highlighting the need to devise optimal eating timing recommendations incorporating food compositions. Key PointsO_ST_ABSQuestionC_ST_ABSWhat are the eating timing patterns for macronutrients and major food groups among US adults from 1999 to March 2020, and how are they associated with mortality? FindingsIn this nationally representative study of 50,264 adults, evening (6-10 pm) consistently contributed to the highest intake proportions of energy, macronutrients, and most food groups, followed by noon (10 am-2 pm), afternoon (2-6 pm), morning (6-10 am), midnight (10 pm-2 am), and predawn (2-6 am). Notably, midnight intake contributed [~]5% of daily energy intake, with a quarter of adults consuming foods at midnight, a nontrivial amount given its potential health risk. The mean durations for energy and macronutrient intake remained [~]12.0 hours, and fasting began after 20:34. Higher midnight and predawn energy intake might be associated with higher mortality; however, associations between eating timing and mortality varied by macronutrients/foods. Males and adults with lower socioeconomic status had higher midnight intake and delayed intake midpoints. MeaningHigh evening intake proportions, midnight consumption, and late fasting onset among US adults raise concerns given the health risk of late eating timing, particularly among males, non-Hispanic Black adults, and adults with low socioeconomic status.