Fasting Improves Glucose Metabolism During Simulated Night-Shift Work, Study Finds

The research, a cluster-randomized controlled trial, revealed that the timing of food intake plays a crucial role in glucose metabolism during simulated night-shift work, and this effect can be effectively modified through a meal re-timing intervention.

Night-shift work has long been linked to poor health outcomes, including increased risks of metabolic disorders such as insulin resistance and type 2 diabetes. These health issues are thought to arise due to the misalignment between the body’s internal clock and external factors, such as food intake, that influence metabolism. Siobhan Banks, University of South Australia, Adelaide, SA, Australia, and colleagues hypothesized that food intake during night shifts may play a role in contributing to this phenomenon.

For this purpose, the researchers conducted an open-label, multi-arm, single-site, parallel-group controlled trial over 6 days at the University of South Australia’s sleep laboratory in Adelaide. The study involved 55 healthy, non-shift-working adults without obesity (age 24.5 ± 4.8 years; BMI 24.8 ± 2.8 kg/m²). Participants were randomly assigned to one of three conditions: fasting-at-night (N=20), snack-at-night (N=17), or meal-at-night (N=18), with one participant withdrawing from each group before the study commenced. Due to the study design, neither participants nor those collecting measurements were blinded, though statistical and laboratory staff were kept unaware of the group assignments. Participants were provided meals at a calculated energy balance, with the macronutrient composition of the meals being similar across the different conditions.

The primary outcomes included a linear mixed-effects model to assess glucose, insulin, and NEFA AUC in response to a 75g OGTT conducted before and after four consecutive nights of simulated shift work, followed by one night of recovery sleep. Insulin sensitivity, insulinogenic, and disposition indexes were also calculated.

The following were the key findings of the study:

• Night-shift work impaired insulin sensitivity, as measured by insulin AUC and the insulin sensitivity index across all conditions.
• Insulin secretion, measured by the insulinogenic index, was significantly increased in the fasting-at-night condition only.
• A day×condition interaction in glucose AUC was observed, showing that glucose tolerance was more impaired in the meal-at-night (+2.00) and snack-at-night (+0.96) conditions compared to the fasting-at-night (+0.34) conditions.
• A day×condition interaction was also found in NEFA AUC, with higher levels in the meal-at-night (+0.07) and snack-at-night (+0.01) conditions compared to the fasting-at-night condition (–0.02).
• No adverse events occurred during the study.

"To date, the potential of manipulating meal timing as a strategy to prevent chronic disease in night-shift working adults has been rarely explored. This study demonstrates that simulated night-shift work led to insulin resistance, which was not alleviated by altering meal timing or size. However, insulin secretion was elevated in the fasting-at-night condition, helping to prevent acute declines in glucose tolerance," the researchers wrote.

"Based on these findings, meal timing advice should be incorporated into dietary guidelines, industry recommendations, and workplace policies to improve health and reduce the burden of metabolic disease among night-shift workers," they concluded.

Reference:

Centofanti, S., Heilbronn, L.K., Wittert, G. et al. Fasting as an intervention to alter the impact of simulated night-shift work on glucose metabolism in healthy adults: a cluster randomised controlled trial. Diabetologia (2024). https://doi.org/10.1007/s00125-024-06279-1