Meal timing may be crucial for night shift workers' health

Led by researchers from the University of South Australia, University of Adelaide and SAHMRI, the NHMRC-funded study involved a six-day trial with 55 adults in the healthy BMI range, who don't usually work night shifts.

Participants stayed at the University of South Australia's Behaviour-Brain-Body Sleep Research Centre and were divided into three groups: those who fasted at night, those who had snacks, and those who ate full meals.

All participants stayed awake for four nights and slept during the day, with a recovery day on day five to re-establish normal sleeping and eating cycles, and blood glucose testing on day six.

Prof Leonie Heilbronn, from SAHMRI and the University of Adelaide, says results showed participants who ate meals or snacks during the nightshift had significantly worse glucose tolerance compared to those who fasted.

"We found that blood glucose skyrocketed for those who ate full meals at night and those who snacked, while the people who fasted at night showed an increase in insulin secretion which kept blood sugar levels balanced," Prof Heilbronn said.

"We know shift workers are more likely to have diabetes, they're more likely to have heart disease, and they're more likely to be overweight. Our research suggests that meal timing could be a major contributor to those issues."

Insulin sensitivity was disrupted among all participants, regardless of their eating habits, adding to the body of evidence that night shifts cause circadian misalignment and impair glucose metabolism.

"When you eat a meal, your body secretes insulin, and that insulin helps your muscles and other tissues to take up glucose. If you become resistant to insulin, then you can't take up that glucose as effectively into your muscles and if it continues, that potentially puts you at risk of diabetes."

Lead investigator UniSA Professor Siobhan Banks says not eating large meals while working night shift and instead eating primarily during the day could be a straightforward intervention to manage health outcomes for many workers.

"This could be easier for people to follow than other more complex diets," Prof Banks said.

Researchers say future trials will investigate whether eating only protein snacks on night shift is a potential solution to satiating hunger without predisposing workers to negative health consequences.