Fasting overnight may help night-shift workers better manage their blood glucose levels and potentially reduce their risk of chronic health conditions, including diabetes, a new study reveals.
While fasting at night maintained glucose tolerance, consuming a meal or snack impaired it.
“It appears, therefore, that avoiding eating at night is an important strategy for mitigating the impacts of night-shift work on glucose metabolism,” the researchers wrote.The study, “Fasting as an intervention to alter the impact of simulated night-shift work on glucose metabolism in healthy adults: a cluster randomised controlled trial”, was published in Diabetologia
Background
Shift work is essential today for keeping many industries, particularly healthcare, running 24/7. People who work night shifts have to alter their sleep schedules to be awake at night and asleep during the day, which can disrupt their body clocks. Previous studies have shown that this disruption can lead to a higher risk of diabetes due to poor sleep quality, physical inactivity, irregular eating habits, unhealthy food choices, and obesity [1,2].
Time-restricted eating involves eating meals only during specific times of the day. This method has been shown to help regulate glucose and fat levels in individuals who work during the day. However, we still do not know how effective it is for those who work at night.
How did the researchers conduct this study?
A team of Australian researchers compared the effects of eating a meal, a snack or fasting overnight on blood glucose tolerance. They enrolled 52 healthy, non-shifting-working adults and divided them into three groups: meal-at-night, snack-at-night, or fasting.
The participants stayed in a controlled lab at the University of South Australia’s Sleep and Chronobiology Laboratory for seven days. The first night, they had a regular sleep schedule from 10 PM to 6 AM. They stayed awake for the next four nights and slept from 10 AM to 5 PM to mimic a night-shift work pattern. They concluded with one last night of sleep, getting eight hours from 10 PM to 6 PM to readjust to a regular sleep schedule.
During the simulated night-shift pattern, participants ate meals at specific times according to their treatment group. All participants had dinner at 7 PM. This was followed at 12:30 AM by either a meal providing about 30% of their daily energy needs (for the meal-at-night group), a snack providing about 10% of their needs (for the snack-at-night group), or nothing (for the fasting group). Each meal and snack had roughly 40% carbohydrates, 33% fat, 17% protein, and 23 grams of fibre.
Participants took an oral glucose tolerance test (OGTT) at the beginning of the study (baseline) and again on the morning of day 7 after a regular sleep schedule. Of note, an oral glucose tolerance test (OGTT) measures how well the body processes carbohydrates. After fasting overnight, an initial blood sample is taken, followed by a sugary solution. Two hours later, a second blood test is done to measure blood glucose levels.
What did they find?
On day seven, participants in the meal and snack groups showed increased fasting and two-hour blood glucose levels compared to their baseline measurements. In contrast, the fasting group did not exhibit this increase; instead, they had lower fasting and two-hour blood glucose levels than the snack and meal groups. Notably, glucose tolerance deteriorated by 11% in the snack group and 25% in the meal group, with the meal group experiencing an increase in two-hour glucose levels of 3.9 mmol/L.
On day 7, the fasting group showed significantly greater insulin secretion than the meal and snack groups. Researchers noted that this increased insulin secretion was crucial in maintaining preserved glucose tolerance.
“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,” Professor Leonie Heilbronn, a professional research fellow at Adelaide Medical School, University of Adelaide said in a university press release.
All participants showed reduced insulin sensitivity, regardless of their eating habits. This supports evidence that working night shifts disrupts body clocks and affects 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,” Professor Helbronn said.
One limitation of the study is that the researchers did not determine if the macronutrient composition of snacks affected glucose tolerance. “Further studies could consider manipulating the carbohydrate content of late-night snacks to determine whether eating a protein-enriched snack would also prevent deteriorations in glucose tolerance,” the researchers wrote.
Meal timing could be a strategy to improve health and reduce the risk of metabolic diseases in night-shift workers.
“This could be easier for people to follow than other more complex diets,” Professor Siobhan Banks, the study’s lead investigator, said.
The Takeaway
This study highlights the potential benefits of overnight fasting for night-shift workers, who often face unique challenges in maintaining their health due to irregular sleep patterns and eating schedules arising from disruptions to their natural circadian rhythms.
Fasting overnight—essentially, not eating after dinner until breakfast the next day—might improve these workers’ ability to regulate glucose, potentially reducing their risk of diabetes and other metabolic disorders.
References
- James, S.M., Honn, K.A., Gaddameedhi, S., & Van Dongen, H.P.A. (2017) Shift work: disrupted circadian rhythms and sleep-implications for health and well-being. Curr Sleep Med Rep. 3(2); 104-112. Doi: 10.1007/s40675-017-0071-6.
- Boivin, D.B., Boudreau, P., & Kosmadopoulos, A. (2021) Disturbance of the circadian system in shift work and its health impact. J Biol Rhythms. 37(1): 3-28. Doi: 10.1177/07487304211064218.
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