Human Resting Energy Expenditure Varies with Circadian Phase

Curr Biol. 2018 Nov 19;28(22):3685-3690.e3. doi: 10.1016/j.cub.2018.10.005. Epub 2018 Nov 8.


There is emerging evidence that circadian misalignment may alter energy expenditure, leading to obesity risk among those with irregular schedules [1-5]. It has been reported that energy expenditure is affected by the timing of sleep, exercise, and meals [6]. However, it is unclear whether the circadian system also modulates energy expenditure, independent of behavioral state and food intake. Here, we used a forced desynchrony protocol to examine whether fasted resting energy expenditure (REE) varies with circadian phase in seven participants. This protocol allowed us to uncouple sleep-wake and activity-related effects from the endogenous circadian rhythm, demonstrating that REE varies by circadian phase. REE is lowest at circadian phase ∼0°, corresponding to the endogenous core body temperature (CBT) nadir in the late biological night, and highest at circadian phase ∼180° in the biological afternoon and evening. Furthermore, we found that respiratory quotient (RQ), reflecting macronutrient utilization, also varies by circadian phase. RQ is lowest at circadian phase ∼240° and highest at circadian phase ∼60°, which corresponds to biological morning. This is the first characterization of a circadian profile in fasted resting energy expenditure and fasted respiratory quotient (with rhythmic profiles in both carbohydrate and lipid oxidation), decoupled from effects of activity, sleep-wake cycle, and diet in humans. The rhythm in energy expenditure and macronutrient metabolism may contribute to greater weight gain in shift workers and others with irregular schedules.

Keywords: carbohydrate oxidation; circadian phase; circadian rhythm; lipid oxidation; metabolic rate; respiratory quotient; resting energy expenditure.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Adult
  • Aged
  • Circadian Rhythm*
  • Diet
  • Energy Metabolism*
  • Female
  • Humans
  • Male
  • Middle Aged
  • Rest / physiology
  • Sleep*
  • Wakefulness*