Reliability estimates for assessing meal timing derived from longitudinal repeated 24-hour dietary recalls.

BACKGROUND: Regulating meal timing may have efficacy for improving metabolic health for preventing or managing chronic disease. However, the reliability of measuring meal timing with commonly used dietary assessment tools needs characterization prior to investigating meal timing and health outcomes in epidemiologic studies.

OBJECTIVE: To evaluate the reliability of estimating meal timing parameters including overnight fasting duration, midpoint of overnight fasting time, number of daily eating episodes, period with largest percentage of daily caloric intake, and late last eating episode (>9pm) from repeated 24-hour dietary recalls (24HR).

DESIGN: Intraclass correlation coefficients, Light's kappa estimates and 95% confidence intervals (CIs) were calculated from repeated 24HR administered in three epidemiologic studies: United States-based IDATA study (n=996, six 24HR collected over 12-months), German EPIC-Potsdam Validation Study (n=134, twelve 24HR collected over 12-months) and EPIC-Potsdam BMBF-II Study (n=725, four 24HR collected over 36-months).

RESULTS: Measurement reliability of overnight fasting duration based on a single 24HR was "poor" in all studies (ICC range 0.27, 95% CI 0.23, 0.32 to 0.46, 95% CI 0.43, 0.50). Reliability was "moderate" with three 24HR (ICC range: 0.53, 95% CI 0.47, 0.58 in IDATA, 0.62, 95% CI 0.52, 0.69 in the EPIC-Potsdam Validation Study, and 0.72, 95% CI 0.70-0.75 in the EPIC-Potsdam BMBF-II Study). Results were similar for midpoint of overnight fasting time and number of eating episodes. Reliability of measuring late eating was "fair" in IDATA (Light's Kappa 0.30, 95% CI 0.21, 0.39) and "slight" in the EPIC-Potsdam Validation study and the EPIC-Potsdam BMBF-II study (Light's Kappa 0.19, 95% CI 0.15, 0.25 and 0.09, 95% CI 0.06, 0.12, respectively). Reliability estimates differed by sex, body mass index, and weekday and season of 24HR administration in some studies.

CONCLUSIONS: Our result show that at least three 24HR over a 1-3-year period are required for reliable estimates of meal timing variables.