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

Mar 5, 2013Obesity (Silver Spring, Md.)

The body’s internal clock raises hunger and appetite in the evening regardless of eating or activities

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Abstract

A peak-to-trough amplitude of 17% in hunger was observed with a trough in the biological morning (8 AM) and a peak in the biological evening (8 PM).

Significant circadian rhythms in appetite for various food types were found, with amplitudes ranging from 14% to 25%.
The biological morning was associated with a decrease in hunger, which may support the extended overnight fast.
The evening peak in appetite could encourage larger meals before the overnight fasting period.
A decline in hunger throughout the night may help prevent fasting-induced hunger increases that disrupt sleep.

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

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