Later circadian timing of food intake is associated with increased body fat

Abstract

Background: Weight gain and obesity have reached alarming levels. Eating at a later clock hour is a newly described risk factor for adverse metabolic health; yet, how eating at a later circadian time influences body composition is unknown. Using clock hour to document eating times may be misleading owing to individual differences in circadian timing relative to clock hour.Objective: This study examined the relations between the timing of food consumption relative to clock hour and endogenous circadian time, content of food intake, and body composition.Design: We enrolled 110 participants, aged 18-22 y, in a 30-d cross-sectional study to document sleep and circadian behaviors within their regular daily routines. We used a time-stamped-picture mobile phone application to record all food intake across 7 consecutive days during a participant's regular daily routines and assessed their body composition and timing of melatonin release during an in-laboratory assessment.Results: Nonlean individuals (high body fat) consumed most of their calories 1.1 h closer to melatonin onset, which heralds the beginning of the biological night, than did lean individuals (low body fat) (log-rank P = 0.009). In contrast, there were no differences between lean and nonlean individuals in the clock hour of food consumption (P = 0.72). Multiple regression analysis showed that the timing of food intake relative to melatonin onset was significantly associated with the percentage of body fat and body mass index (both P < 0.05) while controlling for sex, whereas no relations were found between the clock hour of food intake, caloric amount, meal macronutrient composition, activity or exercise level, or sleep duration and either of these body composition measures (all P > 0.72).Conclusions: These results provide evidence that the consumption of food during the circadian evening and/or night, independent of more traditional risk factors such as amount or content of food intake and activity level, plays an important role in body composition. This trial was registered at clinicaltrials.gov as NCT02846077.

Keywords: body composition; caloric intake; melatonin; metabolism; sleep duration.

© 2017 American Society for Nutrition.

Figures

FIGURE 1

Raster plots (top) of the ∼30-d protocol from 2 participants: 1 with a large phase angle (time difference) between caloric midpoint (average time at which 50% of daily calories were consumed) and DLMO timing (left) and 1 with a small phase angle between caloric midpoint and DLMO timing (right). The x-axis represents the time of day, and the y-axis represents days into the protocol. The black bars represent sleep episodes, gray hatched bars represent the in-laboratory overnight stay for recording percentage of body fat and a DLMO phase assessment (light <4 lux), the black dotted box represents the week of monitoring caloric intake via the time-stamped mobile phone picture food diary, and the open boxes represent caloric events (i.e., any food or beverage that is not water). Note that the in-laboratory assessment could occur before or after the week of monitoring caloric intake but was during the ∼30 d of the protocol. The black arrow on the top and bottom panels denotes the timing of caloric midpoint relative to DLMO. Relative timing of physiologic events in the 2 participants (bottom). The dotted line is the timing of the DLMO, the gray shaded area denotes the phase angle, and the black shaded area denotes habitual sleep timing for that participant relative to DLMO. DLMO, dim-light melatonin onset.

FIGURE 2

Kaplan-Meier survival curves of lean (n = 67; black line) and nonlean (n = 39; gray line) participants’ time to pass caloric midpoint (average time at which 50% of daily calories were consumed) relative to DLMO (A) and clock hour (B). Lean and nonlean participants were defined by their percentage of body fat and by sex (32). The dashed curve and corresponding right y axis represent the average melatonin concentrations of all participants, and the shaded box represents the average habitual timing of sleep of the whole population. P values were derived from log-rank tests. DLMO, dim-light melatonin onset.

FIGURE 3

Correlation between the percentage of calories consumed between 4 h before DLMO and sleep onset (x-axis) and body fat percentage represented as a deviation from the sex-specific criteria of lean (n = 67) or nonlean (n = 39) body composition (y-axis). The horizontal dashed line at 0 represents the threshold to be categorized as lean (<0) or nonlean (>0). Data were analyzed with the Pearson correlation. DLMO, dim-light melatonin onset.

FIGURE 4

Correlations between 24-h total sleep time (x-axis) and the time difference of the latest daily calories relative to DLMO timing (i.e., time of latest calories minus DLMO) represented as phase angle (n = 100) (y-axis) (A) and clock hour of the latest daily calories (n = 104) (y-axis) (B). Data were analyzed with the Pearson correlation. DLMO, dim-light melatonin onset.