Study: Nighttime eating affects body clock, can lead to glucose intolerance

Night shift workers' eating habits may affect their body's ability to process sugars, increasing their risk for diabetes, according to a new study. Photo by Dayamay/Pixabay
Night shift workers' eating habits may affect their body's ability to process sugars, increasing their risk for diabetes, according to a new study. Photo by Dayamay/Pixabay

Dec. 3 (UPI) -- Eating at night may increase a person's risk for glucose intolerance, or prediabetes, a study published Friday by the journal Science Advances found.

Confining meals to daytime can help maintain healthy blood glucose levels, allowing the body to more effectively process sugars, the researchers said.


After assessing the effects of nighttime eating on night shift workers, it appears that food consumption during the overnight hours causes a misalignment between the body's central and peripheral circadian "clocks," they said.

Circadian clocks are the body's natural timekeepers that regulate physical, mental and behavioral changes throughout the day.

In addition to applying to night shift workers, the findings could have implications for others who eat meals at atypical times, such as those experiencing jet lag or sleep disorders, or people who tend to sleep late on weekends, the researchers said.


"Of the participants studied, those with the biggest disruption of their circadian system ... showed the largest impairment of glucose tolerance," study co-author Frank A.J.L. Scheer said in a statement provided by Brigham & Women's Hospital in Boston, at which he works.

These participants had evidence of "misalignment between their central circadian clock and their endogenous circadian glucose rhythms," said Scheer, director of the Medical Chronobiology Program in the hospital's sleep and circadian disorders division.

Glucose intolerance results in high levels of the sugar in the bloodstream, a precursor for Type 2 diabetes, a condition that affects 30 million people in the United States, according to the Centers for Disease Control and Prevention.

In people with Type 2 diabetes, the body is less able to absorb sugar from the bloodstream into its tissues, causing dangerously high levels that can lead to serious health complications.

Night shift workers, who typically sleep during daytime and eat in the evening, have as much as a 60% higher risk for developing Type 2 diabetes compared with day-shift workers, research suggests. That is perhaps because of the body's reduced ability to process sugars overnight.

Such metabolic processes are governed by the body's circadian rhythms, which rise and fall during the 24-hour day, according to the CDC.


The brain's circadian clock sets the timing for many circadian rhythms, which regulate processes such as sleep and wake cycles, hormonal activity and eating and digesting.

For this study, Scheer and his colleagues assessed the effects of nighttime eating in 19 healthy young participants who stayed awake for 32 hours in a highly controlled, dimly lit environment, where they kept constant body posture and consumed identical snacks every hour.

Following this period, the participants engaged in a simulated night work schedule and followed one of two eating schedules, the researchers said.

One group ate during the nighttime to simulate a schedule typical among night shift workers, while the other ate during daytime, thus aligning the meal schedule to that of the central circadian clock.

Then, participants followed a second, 40-hour constant routine schedule to assess the effects of the meal schedules on their circadian rhythms.

Participants who ate during nighttime had increased blood glucose levels, while those who ate only during daytime experienced no significant changes, the data showed.

In addition, nighttime eating reduced pancreatic beta-cell function, which impacted affected participants' ability to process sugars, the researchers said.

Beta cells produce insulin, a hormone that helps the body process sugar.


Nighttime eating also caused a misalignment in participants' central circadian clocks, as estimated from changes in body temperature and blood glucose levels, according to the researchers.

Meanwhile, circadian rhythms that govern body temperature and glucose levels remained aligned when participants ate meals during the daytime, even with mistimed sleep.

"These results indicate that meal timing was primarily responsible for the reported effects on glucose tolerance and beta cell function," Scheer said.

"While the central circadian clock still was on Boston time, the endogenous circadian glucose rhythms suggest that some peripheral clocks, perhaps those in the liver, had shifted dramatically to a time zone in Asia," he said.

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