CU study: Working the night shift increases risk of weight gain

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A University of Colorado study showed that workers who are on the night shift are more prone to gaining weight.

BOULDER, Colo. — Working different shifts can make you tired, but new research shows it can also cause you to pack on the pounds.

A study from the University of Colorado shows workers on the night shift might expend less energy and be more prone to weight gain.

One theory is shift work goes against our nature. It requires the biological day to occur at night and vice versa. Many people never really adapt to this and a sluggish metabolism can be the result.

The study, published in the Proceedings of the National Academy of Sciences, looked at 14 healthy adults who spent six days at the University of Colorado Hospital’s Clinical and Translational Research Center.

The participants followed a normal schedule the first two days. The next three days, they shifted their work schedule before the routines were reversed.

“When people are on a shift work-type schedule, their daily energy expenditure is reduced and unless they were to reduce their food intake, this by itself could lead to weight gain,” said Kenneth Wright, director of CU’s Sleep and Chronobiology Laboratory and senior author of the paper.

The meals were carefully controlled during the study and each participant was given the same eight-hour sleep opportunity. But the energy used by the participants went down when the schedule shifted.

“Shift work goes against our fundamental biology,” Wright said. “Shift work requires our biological day to occur at night and our biological night to occur during the day and that’s very difficult to achieve because the sun is such a powerful cue. We can have some change in our clock—a couple of hours—but then on days off, it goes right back. Shift workers never adapt.”

Researchers also found participants burned more fat when they slept during the day than at night. Wright said more research would be needed to determine if the fat-burning phenomenon of actual shift workers.

“What we can say is that it’s perhaps even more important to have a healthy diet for shift workers as well as a healthy amount of physical activity,” Wright said.

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