"The Association Between Timing of Dietary of Intake and Healthy Aging" Public Health/Epidemiology. 

Committee: 

Samaneh Farsijani (advisor), epidemiology
Anne B. Newman, epidemiology
Tina Costacou, epidemiology
Ying Ding, biostatistics

Abstract: The timing of dietary intake, known as chrononutrition, plays a critical role in regulating circadian rhythms and influencing health. While current dietary guidelines emphasize diet quantity and quality, they largely overlook meal timing. Emerging evidence links chrononutrition to body composition and metabolic health, yet its impact on aging-related outcomes, such as muscle health and survival, remains underexplored. As the U.S. population ages, incorporating meal timing into dietary strategies may promote healthy aging and longevity.

This dissertation aimed to: 1) assess associations between chrononutrition behaviors (e.g., first/last intake time, eating window, and frequency) and muscle health in older adults; 2) evaluate the relationship between eating window and all-cause, cardiovascular, and cancer mortality in U.S. adults aged >19 years, with exploration of biological and demographic modifiers; and 3) identify within-day calorie intake distribution patterns using trajectory modeling and assess their associations with mortality risks.

In Aim 1, I observed that a longer eating window, earlier first intake, and later last intake were associated with better muscle mass and strength in older adults (Study of Muscle, Mobility, and Aging; N=828). Aim 2 used NHANES 2003–2018 (N=33,052) to demonstrate a U-shaped relationship between eating window and mortality, with windows <8 or >15 hours/day linked to higher mortality risk compared to ~12-hour windows. Shorter windows were particularly associated with cardiovascular mortality among older adults. Aim 3 identified four calorie distribution patterns: morning-skewed, midday-skewed, evening-skewed, and balanced midday-evening (NHANES 2005–2018; N=28,425). Morning- and evening-focused patterns were associated with higher all-cause mortality risk compared to the balanced pattern.

These findings highlight the critical role of chrononutrition in healthy aging and emphasize the importance of considering meal timing alongside dietary quality and quantity. By providing evidence for tailored dietary recommendations, this work supports public health efforts to address aging-related health challenges, reduce mortality risks, and improve population health. These insights align with NIH's emphasis on precision nutrition and pave the way for future research on causal mechanisms and interventions targeting meal timing.