Circadian timing of eating and BMI among adults in the American Time Use Survey

Abstract

Background/objectives: Experimental studies of time-restricted eating suggest that limiting the daily eating window, shifting intake to the biological morning, and avoiding eating close to the biological night may promote metabolic health and prevent weight gain.

Subjects/methods: We used the Eating & Health Module of the 2006-2008 and 2014-2016 American Time Use Survey to examine cross-sectional associations of timing of eating in relation to sleep/wake times as a proxy for circadian timing with body mass index (BMI). The analytical sample included 38 302 respondents (18-64 years; BMI 18.5-50.0 kg/m²). A single 24-hour time use diary was used to calculate circadian timing of eating variables: eating window (time between first and last eating activity); morning fast (time between end of sleep and start of eating window); and evening fast (time between end of eating window and start of sleep). Multinomial logistic regression and predictive margins were used to estimate adjusted population prevalences (AP) by BMI categories and changes in prevalences associated with a one-hour change in circadian timing of eating, controlling for sociodemographic and temporal characteristics.

Results: A one-hour increase in eating window was associated with lower adjusted prevalence of obesity (AP = 27.1%, SE = 0.1%). Conversely, a one-hour increase in morning fast (AP = 28.7%, SE = 0.1%) and evening fast (AP = 28.5%, SE = 0.1%) were each associated with higher prevalence of obesity; interactions revealed differing patterns of association by combination of eating window with morning/evening fast (p < 0.0001).

Conclusions: Contrary to hypotheses, longer eating windows were associated with a lower adjusted prevalence of obesity and longer evening fasts were associated with a higher prevalence of obesity. However, as expected, longer morning fast was associated with a higher adjusted prevalence of obesity. Studies are needed to disentangle the contributions of diet quality/quantity and social desirability bias in the relationship between circadian timing of eating and BMI.

Figure 1

Illustration of circadian timing of eating variables from two hypothetical days in the American Time Use Survey Eating and Health Module (ATUS-EHM), from 4:00 on Day 1 to 3:59 on Day 2. The solid black bars indicate eating activities, and their width indicates duration, and the dotted bars indicate sleep. While Panel A and Panel B both have the same sleep/wake activity pattern, the timing of eating in relation to sleep and wake (i.e., circadian timing of eating) show different patterns. In Panel A, morning fast is short, eating window lasts about 14 h, and eating continues until approximately an hour before bedtime. In contrast, Panel B displays a longer morning fast, a shorter eating window and a longer evening fast.

Figure 2

Population-adjusted mean, standard deviation, and range of circadian timing of eating characteristics by BMI category among N= 38 302 respondents from the American Time Use Survey Eating and Health Module (ATUS-EHM). The top panel displays eating window duration, the middle panel displays morning fast duration, and the lower panel displays evening fast duration by BMI category (i.e., obese, overweight, normal weight). In each panel, the vertical center line indicates the population-adjusted mean value, the lower and upper box boundaries indicate the standard deviation of the mean, and the horizontal line indicates the range.