Disrupting circadian rhythm causes changes in the brain that increase hunger, according to a recent study conducted by researchers from the University of Bristol. The study focused on the impact of “circadian misalignment,” commonly experienced by night shift workers and frequent flyers, on the brain’s regulation of appetite.
The circadian rhythm, our internal biological clock, regulates the production of hormones called glucocorticoids, which play a role in metabolism and appetite. Glucocorticoids directly influence the release of neuropeptides in the brain that control hunger. Some of these neuropeptides increase appetite while others decrease it. Cortisol, also known as the body’s natural steroid, is the main glucocorticoid in humans.
To investigate how circadian misalignment affects hunger regulation, the researchers conducted experiments using rats with their adrenal glands removed. These rats were divided into two groups: a control group and a “jet-lagged” group. The control group received an infusion of corticosterone, the rat equivalent of cortisol, that mimicked the hormone’s release according to the light-dark cues of a normal day-night cycle. The treatment group also received corticosterone, but it was shifted out-of-phase by 12 hours with the light-dark cues.
The researchers observed that the misalignment of light-dark cues led to dysregulation of one of the hunger-inducing neuropeptides, neuropeptide Y (NPY), in the out-of-phase rats. This caused them to consume significantly more food during their inactive phase. The control group rats consumed 88.4% of their daily calorie intake during their active phase and only 11.6% during their inactive phase. However, the jet-lagged rats consumed 53.8% of their daily calories during their inactive phase, without an increase in activity. This equated to a staggering 460% more food consumption for the treatment group during their inactive phase compared to the control group.
The researchers also found that gene expression was markedly altered in the out-of-phase rats. These findings suggest that when daily glucocorticoid levels are out of sync with light and dark cues, neuropeptides that affect appetite become significantly disordered.
While there was no observable change in body weight over the short duration of the study, the researchers noted the striking changes in feeding behavior were evident and consistent throughout the experiment. They believe that the neuropeptides identified in their study could be potential targets for drug treatments for eating disorders and obesity.
Furthermore, the researchers offered advice for those trying to overcome nighttime hunger through willpower alone. For individuals working night shifts long-term, they recommend maintaining exposure to daylight, engaging in cardiovascular exercise, and regulating mealtimes. However, they highlight the difficulty of overriding the internal messages in the brain that drive increased appetite. As a result, they are designing studies to explore rescue strategies and pharmacological interventions.
The study provides insights into how chronic stress and sleep disruption contribute to excessive calorie consumption. Understanding the impact of circadian misalignment on appetite regulation may lead to new approaches for treating eating disorders and obesity.
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1. Source: Coherent Market Insights, Public sources, Desk research
2. We have leveraged AI tools to mine information and compile it
