Circadian rhythms regulate the body’s many physiological processes, including those influencing appetite. Disrupted rhythms, such as those occurring with shift work or jet lag, can alter appetite, contributing to weight gain. A recent study showed that rats with jet lag ate 460 percent more food during their resting phase than non-jet-lagged rats.

Researchers studied two groups of rats: one that experienced typical light/dark cues (a control group) and one that experienced reversed cues (a “jet-lagged” group) for five days. They monitored the animals' food intake and measured levels of glucocorticoids, a class of hormones that regulate behavior, sleep-wake cycles, and metabolism.

They found that jet-lagged animals demonstrated dysregulated orexigenic hypothalamic neuropeptide, a glucocorticoid hormone that regulates appetite. This dysregulation increased their desire to eat during their inactive phase (when they typically rest), consuming 460 percent more food than the control group. The overeating rats didn’t gain weight during the study period, likely due to the short duration.

These findings suggest that circadian rhythm disruption alters glucocorticoid levels in rats, driving increased food consumption. Although the animals didn’t gain weight during the study, longer disruption (as in shift work) may drive considerable weight gain. The study’s authors posited that maintaining a consistent daily schedule and regular meals may help mitigate the effects of circadian rhythm disruption. Learn more about how shift work and jet lag influence circadian rhythms in this clip featuring Dr. Satchin Panda.

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