Bristol University of Scientists have uncovered why night shift work is related to changes in appetite in a brand new University of Bristol-led study. The findings, published in Communications Biology, could help the thousands and thousands of people that work through the night and struggle with weight gain.

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Scientists from Bristol and the University of Occupational and Environmental Health in Japan sought to know how ‘circadian misalignment’ — a phenomenon commonly related to ‘jet lag’ whereby the body’s biological clock is disrupted — affects the hormones chargeable for regulating appetite.

Prevalent in night shift staff, on this recent study, the international team reveals how circadian misalignment can profoundly alter the brain’s regulation of hormones controlling hunger to the detriment of metabolic health.

The team focused on glucocorticoid hormones within the adrenal gland, which regulate many physiological functions, including metabolism and appetite. Glucocorticoids are known to directly regulate a gaggle of brain peptides controlling appetitive behavior, with some increasing appetite (orexigenic) and a few decreasing appetite (anorexigenic).

In an experiment using animal models, comprising a control group and an out-of-phase ‘jet-lagged’ group, the team found misalignment between light and dark cues led the out-of-phase group’s orexigenic hypothalamic neuropeptides (NPY) to turn into dysregulated, driving an increased desire to eat significantly more in the course of the inactive phase of the day.

Strikingly, the team discovered that rats within the control group ate 88.4% of their every day intake during their energetic phase and only 11.6% during their inactive phase. In contrast, the ‘jet-lagged’ group consumed 53.8% of their every day calories during their inactive phase (without a rise in activity during this time). This equated to almost five times more (460% more) than the control group consumed in the course of the inactive phase. These results show that it’s the timing of consumption that has been affected.

This discovery revealed how completely and significantly disordered the neuropeptides turn into when every day glucocorticoid levels are out of sync with light and dark cues. Nevertheless, the authors suggest the neuropeptides identified on this study could also be promising targets for drug treatments adapted to treat eating disorders and obesity.

Dr Becky Conway-Campbell, Research Fellow in Bristol Medical School: Translational Health Sciences (THS) and the study’s senior writer, said: “For people working throughout the night, a reversed body clock can play havoc with their health.

“For individuals who are working night shifts long-term, we recommend they fight to keep up daylight exposure, cardiovascular exercise and mealtimes at regulated hours. Nevertheless, internal brain messages to drive increased appetite are difficult to override with ‘discipline’ or ‘routine’ so we’re currently designing studies to evaluate rescue strategies and pharmacological intervention drugs. We hope our findings also provide recent insight into how chronic stress and sleep disruption results in caloric overconsumption.”

Stafford Lightman, Professor of Medicine at Bristol Medical School: THS and co-senior writer on the study, added: “The adrenal hormone corticosterone, which will likely be secreted in a circadian manner, is a big consider the every day control of brain peptides that regulate appetite. Moreover, once we disturb the traditional relationship of corticosterone with the day-to-night light cycle, it leads to abnormal gene regulation and appetite in the course of the period the animals normally sleep.

“Our study shows that once we disturb our normal bodily rhythms this in turn disrupts normal appetite regulation in a way that’s a minimum of partially a results of desynchrony between adrenal steroid hormone production and the timing of the sunshine and dark cycle.”

Dr. Benjamin Flynn, one in every of the study’s co-authors who conducted the study while at Bristol but is now based on the University of Bath, added: “That is further evidence of how phase shift ‘jet-lag’ affects feeding behaviors and neuronal gene expression – data essential for shift work co-morbidity research.”

The Medical Research Council funded this research.