Fasting during night shift better maintains glucose tolerance vs. eating meals, snacks
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Key takeaways:
- Glucose tolerance was more impaired in the meal-at night and snack at-night groups compared with the fasting-at-night group.
- Meal timing advice may reduce metabolic disease burden on night-shift workers.
Healthy adults who fasted for the entirety of simulated night-shift work displayed compensatory hyperinsulinemia and maintained glucose tolerance compared with participants who consumed a meal or snack, study results showed.
“This knowledge about eating in alignment with circadian clocks and minimizing food consumption at night will help people better control their glucose,” Siobhan Banks, PhD, director of the Behavior-Brain-Body Research Centre at the University of South Australia and research professor at the UniSA Justice & Society, told Healio.
Night-shift workers, who comprise approximately 20% of the working population, will typically redistribute their meals to eat in the evening, but doing so may contribute to the increases risk for obesity and type 2 diabetes seen among this group, according to the researchers.
Because time-restricted eating (TRE) has emerged as an intervention to improve health and glucose control among nonshift workers, Banks and colleagues investigated the effects of TRE — by comparing eating a meal vs. eating a snack vs. fasting — on glucose metabolism during simulated nightshift work in healthy nonshift-working adults.
The three-arm, parallel-group cluster randomized controlled trial included 55 healthy, nonshift-working participants aged 18 to 50 years (mean age, 24.5 years; 23 women; mean BMI, 24.8 kg/m2) from the general population who slept between 7 to 9 hours habitually.
Researchers used cluster randomization to assign participants to fasting-at-night (n = 20), snack-at-night (n = 17) or meal-at-night (n = 18) groups, with the meals having similar macronutrient composition, at the University of South Australia’s sleep laboratory.
The primary outcomes of the trial included glucose, insulin and nonesterified fatty acids (NEFA) area under the curve following a 75 g oral glucose tolerance test conducted at baseline and after 4 nights of shift work plus 1 night of recovery sleep. The researchers also calculated insulin sensitivity and insulinogenic indexes.
Among the 52 evaluable participants, the researchers found that glucose AUC was higher in response to the OGTT when returning to a daytime schedule in the meal-at-night (P < .001) and snack-at-night (P < .01) groups, but not the fasting-at-night group, compared with baseline.
Concerning insulin AUC, researchers observed a condition-only effect (P = .047), with higher AUC in the fasting-at-night group vs. the other groups.
Further, NEFA showed a condition by day (P = .001) and a condition (P = .024) effect, with higher AUC from baseline in only the meal-at-night group (P < .001).
The researchers also observed a condition by day interaction (P =.037) and a condition effect (P < .001) for the insulinogenic index, with higher values from baseline in the fasting-at-night group (P = .03).
The oral insulin sensitivity index showed an effect by day only (P = .016).
Overall, glucose tolerance was impaired in the meal-at night (2; 95% CI, 1.45-2.56; P < .001) and snack at-night (0.96; 95% CI, 0.36-1.56; P = .022) groups compared with the fasting-at-night (0.34; 95% CI, –0.21 to 0.89) group.
The researchers noted several limitations to the study, including lack of analysis of C-peptide.
“The current study clearly shows that simulated night-shift work induced insulin resistance, which was not rescued by altering either meal timing or meal size,” Banks and colleagues wrote. “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.”
Future studies could follow workers across different shifts to understand how to best integrate this approach into a work environment, Banks told Healio.
For more information:
Siobhan Banks, PhD, can be reached at Siobhan.Banks@unisa.edu.au.
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