The internal circadian clock increases hunger and appetite in the evening independent of food intake and other behaviors

Authors

  • Frank A.J.L. Scheer,

    Corresponding author
    1. Medical Chronobiology Program, Division of Sleep Medicine, Department of Medicine, Brigham and Women's Hospital, Boston, MA, USA
    2. Division of Sleep Medicine, Harvard Medical School, Harvard University, Boston, MA, USA
    • Medical Chronobiology Program, Division of Sleep Medicine, Brigham and Women's Hospital, Boston, MA, USA

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  • Christopher J. Morris,

    1. Medical Chronobiology Program, Division of Sleep Medicine, Department of Medicine, Brigham and Women's Hospital, Boston, MA, USA
    2. Division of Sleep Medicine, Harvard Medical School, Harvard University, Boston, MA, USA
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  • Steven A. Shea

    1. Medical Chronobiology Program, Division of Sleep Medicine, Department of Medicine, Brigham and Women's Hospital, Boston, MA, USA
    2. Center for Research on Occupational and Environmental Toxicology, Oregon Health and Science University, Portland, OR, USA
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  • Disclosure: The authors declared no conflict of interest.

  • Funding agencies: This research was supported by NIH-R01-HL76409 and NIH-K24 HL076446 to SAS, NCRR GCRC M01 RR02635; NIH-P30-HL101299 and NIH-R01-HL094806 in support of FAJLS; National Space Biomedical Research Institute through NASA NCC 9-58 in support of CJM.

Abstract

Objective:

Despite the extended overnight fast, paradoxically, people are typically not ravenous in the morning and breakfast is typically the smallest meal of the day. We assessed whether this paradox could be explained by an endogenous circadian influence on appetite with a morning trough, while controlling for sleep/wake and fasting/feeding effects.

Design and Methods:

Twelve healthy non-obese adults (six males; age, 20-42 years) were studied throughout a 13-day laboratory protocol that balanced all behaviors, including eucaloric meals and sleep periods, evenly across the endogenous circadian cycle. Participants rated their appetite and food preferences by visual analog scales.

Results:

There was a large endogenous circadian rhythm in hunger, with the trough in the biological morning (8 AM) and peak in the biological evening (8 PM; peak-to-trough amplitude = 17%; P = 0.004). Similarly-phased significant endogenous circadian rhythms were present in appetites for sweet, salty and starchy foods, fruits, meats/poultry, food overall, and for estimates of how much food participants could eat (amplitudes 14-25%; all P < 0.05).

Conclusions:

In people who sleep at night, the intrinsic circadian evening peak in appetite may promote larger meals before the fasting period necessitated by sleep, whereas the circadian morning trough would theoretically facilitate the extended overnight fast. Furthermore, the circadian decline in hunger across the night would theoretically counteract the fasting-induced hunger increase that could otherwise disrupt sleep.

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