Conceptualization and assessment of 24hr timing of eating and energy intake: a methodological systematic review of the chronic disease literature

Authors: O'CONNOR, SYDNEY - National Institutes Of Health (NIH); O'Connor, Lauren; HIGGINS, KELLY - Former ARS Employee; BELL, BROOKE - Tufts University; KRUEGER, EMILY - National Institutes Of Health (NIH); RAWAL, RITA - University Of Maryland; HARTMULLER, REILEY - National Institutes Of Health (NIH); HERRICK, KRISTEN - National Institutes Of Health (NIH); REEDY, JILL - National Institutes Of Health (NIH); CZAJKOWSKI, SUSAN - National Institutes Of Health (NIH); SHAMS-WHITE, MARISSA - National Institutes Of Health (NIH)

Submitted to: Advances in Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/16/2024
Publication Date: N/A
Citation: N/A

Interpretive Summary: Not only what we eat, but when we eat may also contribute to chronic disease risk for those living in the US, i.e. chrononutrition. The past Dietary Guidelines Advisory Committee reviewed evidence about timing of eating in relation to obesity risk, but concluded that terminology and methods of measuring timing of eating was too inconsistent across studies to draw conclusions. The objective of this systematic review of the literature was to summarize the terminology and methods used in timing of eating research to identify common themes. The methods used in 259 published articles about timing of eating and risk for obesity, cardiometabolic disease, and cancer were reviewed and summarized. Overall, terminology related to timing of eating varied widely across studies, often incorporating multiple aspects of timing of eating (e.g., fasting duration, time of first meal, percent of energy consumed by a certain time of day). Methods of measuring timing of eating were often not validated and most often only captured less than a few days of intake. The results of this paper can be used tto support development of a framework for chrononutrition research, which could help standardize terminology and promote best practices for measuring timing of eating to future dietary guidance.

Technical Abstract: Timing of eating (TOE) and energy intake (TOEI) has important implications for chronic disease risk beyond diet quality. The 2020 Dietary Guidelines Advisory Committee recommended developing consistent terminology to address the lack of TOE/TOEI standardization. The primary objective of this methodological systematic review was to characterize the conceptualization and assessment of TOE/TOEI within the chronic disease literature (International Prospective Register of Systematic Reviews registration number: CRD42021236621). Literature searches in Cumulative Index to Nursing and Allied Health Literature (CINAHL) Plus, Embase, PubMed, and Scopus were limited to English language publications from 2000 to August 2022. Eligible studies reported the association between TOE/TOEI and obesity, cardiovascular disease, type 2 diabetes mellitus, cancer, or a related clinical risk factor among adults (19 y) in observational and intervention studies. A qualitative synthesis described and compared TOE/TOEI conceptualization, definitions, and assessment methods across studies. Of the 7579 unique publications identified, 259 studies (observational [51.4 %], intervention [47.5 %], or both [1.2 %]) were eligible for inclusion. Key findings indicated that most studies (49.6 %) were conducted in the context of obesity and body weight. TOE/TOEI variables or assigned conditions conceptualized interrelated aspects of time and eating or energy intake in varying ways. Common TOE/TOEI conceptualizations included the following: 1) timepoint (specific time to represent when intake occurs, such as time of breakfast [74.8 %]); 2) duration (length of time or interval when intake does/does not occur, such as “eating window” [56.5 %]); 3) distribution (proportion of daily intake at a given time interval, such as “percentage of energy before noon” [29.8 %]); and 4) cluster (grouping individuals based on temporal ingestive characteristics [5.0 %]). Assessment, definition, and operationalization of 24-h TOE/TOEI variables varied widely across studies. Observational studies most often used surveys or questionnaires (28.9 %), whereas interventions used virtual or in-person meetings (23.8 %) to assess TOE/TOEI adherence. Overall, the diversity of terminology and methods solidifies the need for standardization to guide future research in chrononutrition and to facilitate inter-study comparisons.