Brain changes from shift work and jet lag increase appetite

Altered feeding behavior due to circadian phase shifting of hormones.


Researchers from University of Bristol and the University of Occupational and Environmental Health in Japan investigated how “circadian misalignment,” a condition often linked to jet lag, disrupts the body’s internal clock and affects the hormones that manage hunger

This study, particularly relevant for night shift workers, found that circadian misalignment can significantly impact how the brain controls hormones related to appetite, potentially harming metabolic health. They focused on glucocorticoid hormones in the adrenal gland, which regulate metabolism and hunger. These hormones directly influence specific brain signals that either increase appetite (orexigenic) or decrease it (anorexigenic).

In an animal study with a control group and a ‘jet-lagged’ group, the team found that when the internal body clock was out of sync with light and dark cues, the ‘jet-lagged’ group’s appetite-controlling brain signals (NPY) went haywire, causing them to eat a lot more during their inactive period. Surprisingly, the control group mainly ate during their active time, but the ‘jet-lagged’ group consumed almost five times more during their idle time. This means that when they ate, it was affected.

This discovery highlights how severely these brain signals are disrupted when daily hormone levels don’t match the body’s natural rhythms. The researchers suggest that the identified brain signals could be potential targets for developing drugs 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 author, said: “For people working throughout the night, a reversed body clock can play havoc with their health.”

“For those working night shifts long-term, we recommend they try to maintain daylight exposure, cardiovascular exercise, and mealtimes at regulated hours. However, internal brain messages to drive increased appetite are difficult to override with ‘discipline’ or ‘routine,’ so we are currently designing studies to assess rescue strategies and pharmacological intervention drugs. We hope our findings also provide new insight into how chronic stress and sleep disruption lead to caloric overconsumption.” He added

Stafford Lightman, a Professor of Medicine at Bristol Medical School and co-senior author of the study, explained that “the adrenal hormone corticosterone, typically produced in a daily cycle, plays a crucial role in regulating the brain’s appetite-related signals. When changes in the day-night light pattern disrupt this natural cycle, it leads to abnormal gene activity and appetite disturbances, particularly during the animals’ sleep period. The study demonstrates how disrupting our natural rhythms can affect appetite regulation, partly due to the mismatch between adrenal hormone production and the light-dark cycle timing.”

Dr. Benjamin Flynn, a co-author of the study who conducted the research while at Bristol and is now at the University of Bath, emphasized that their findings provide additional evidence of how ‘jet lag’ disrupts feeding patterns and the expression of genes in brain neurons, which is crucial information for research related to health issues associated with shift work.

This study uncovers the disruptive effects of circadian misalignment, akin to jet lag, commonly encountered by shift workers, on the body’s appetite regulation. It emphasizes the significance of comprehending how disturbances to the internal body clock can impact eating habits, offering valuable insights into health concerns associated with shift work.

Journal reference:

  1. Yoshimura, M., Flynn, B.P., Kershaw, Y.M. et al. Phase-shifting the circadian glucocorticoid profile induces disordered feeding behavior by dysregulating hypothalamic neuropeptide gene expression. Communications Biology. DOI: 10.1038/s42003-023-05347-3.