Fasting During Night Shifts Improves Glucose Control

Credit: Adobe Stock/Kateryna

Night-shift work impaired insulin sensitivity across three groups: fasting-at-night, snack-at-night or meal-at-night. However, those who ate meals or snacks at night had worsened glucose tolerance compared with those who fasted.

Results demonstrated meal timing during night shifts significantly affects glucose metabolism, but fasting at night may mitigate these effects.

Having an irregular work schedule—which accounts for approximately 20% of the working population—means shift workers often sleep during the day and are awake at night. Among workers who are non-shift, meals eaten late at night have been linked to increased weight, even after controlling for duration and sleep timing. Eating later in the day also reduces the efficacy of weight loss programs, regardless of energy intake, sleep and dietary composition. Therefore, eating in a time-restricted period is a new therapeutic intervention to improve lipid metabolism and glucose levels among these workers. However, there is a lack of biological data into improved outcomes in shift-workers.

“Night-shift workers gain more weight after starting their jobs, have higher rates of obesity and type 2 diabetes (even after adjusting for lifestyle and socioeconomic circumstances), and those with type 2 diabetes have poorer glucose control,” wrote a team of investigators led by Stephanie Centofanti. PhD, associated with the Behaviour-Brain-Body Research Centre, UniSA Justice and Society, University of South Australia, Adelaide, Australia. “However, night-shift workers also alter their eating patterns, habitually eating during the night shift. This transferal in eating behaviors could contribute to increased disease risk.”

To analyze food timing on glucose metabolism during night-shift work, investigators enrolled 52 healthy adults. Patients were randomized into three groups: fasting-at-night, snack-at-night and meal-at-night. Primary endpoints were glucose and insulin following four nights of simulated shift work plus one night of recovery sleep when compared with baseline. Other outcomes included fasting and postprandial glucose and insulin responses to a breakfast that was high in carbs after the first and fourth night of shiftwork as well as sleep health at baseline and after the third night of shift work and during the recovery sleep period.

During the study period, subjects who ate either a meal or a snack at 12:30 AM had a lower glucose tolerance. Patients who fasted at night had compensatory hyperinsulinemia and were able to maintain glucose tolerance. Therefore, investigators believed meal timing to be an effective intervention to mitigate any potential impairments in glucose metabolism due to night-shift working hours. Even though a snack may be more tolerable than overnight fasting, patients in the snack-at-night group still had more glucose tolerance impairment when compared with the fasting-at-night group.

No serious adverse events were reported during the trial.

Some limitations mentioned by investigators included conducting the study under simulated conditions, which may not reflect real-world outcomes. Future research should also consider manipulating the carbohydrate content of late-night snacks to assess if protein-rich snacks would similarly inhibit glucose tolerance. Additionally, optimal meal timing should be examined to determine whether night-shift workers could adjust meals in accordance with a shift in central and peripheral clocks.

“Simulated night-shift work induced insulin resistance, which was not rescued by altering either meal timing or meal size,” investigators concluded. “However, insulin secretion was increased in the fasting-at-night condition, which prevented acute deteriorations in glucose tolerance. Meal timing advice should be considered for existing dietary guidelines, industry recommendations and workplace policy to improve health and reduce the burden of metabolic disease on night-shift workers.”