How working night shifts messes up appetite and food habits

Scientists reveal how working night shifts interferes with appetite, hunger and food habits, sometimes resulting in weight gain.

The disruption in the body's biological clock, or circadian misalignment, brought about by working night shifts affects the hormones which regulate appetite, the team of scientists, led by the University of Bristol, UK, said.

Circadian misalignment is also commonly associated with the phenomenon of 'jet-lag'.

The team focussed on the adrenal gland, situated near the kidney, which produces hormones that control many physiological functions including metabolism and appetite, called glucocorticoid hormones.

A misalignment between light and dark cues led to a disturbance in the functioning of these hormones that then affected the appetite of the jet-lagged group of animals, driving an increased desire to eat significantly more during the inactive phase of the day, the scientists said in their study published in the journal Communications Biology.

They said that their findings reveal how circadian misalignment can profoundly alter food habits much to the detriment of metabolic health and that they could help the millions of people that work through the night and struggle with weight gain.

The glucocorticoid hormones in the adrenal glands directly regulate a group of brain peptides controlling appetitive behaviour, with some increasing appetite (orexigenic) and some decreasing appetite (anorexigenic).

In this study, the jet-lagged group's orexigenic hypothalamic neuropeptides (NPY) became dysregulated, which the authors say may be promising targets for drug treatments adapted to treat eating disorders and obesity.

Further, the team discovered that while the control rats ate about 90 per cent of their daily intake during their active phase and only 11 per cent during their inactive phase, the jet-lagged rats consumed about 54 per cent of their daily calories during their inactive phase, with no increased physical activity in this time.

This was roughly five-times more than what the control rats consumed during the inactive phase, suggesting that it was the timing of calorie consumption that was affected, the scientists said.

"For those who are 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," said senior author Becky Conway-Campbell, Research Fellow at Bristol.