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Shift workers working long hours tend to gain weight, putting them at a greater risk of metabolic diseases and stress factors.

Credit: Ipek Obek

A recent Penn Medicine study supports a theory that people who work irregular hours are more likely to gain weight and develop diabetes. 

The study, published in Science Advances on Oct. 27, studied circadian desynchrony in mice, which is a theory that the disruption of your internal clock leads to “poor outcomes,” Penn Medicine News reported. The study found that working irregular hours can harm one's metabolism and lead to weight gain and diabetes. The study was led by director of Penn Medicine’s Institute for Diabetes, Obesity, and Metabolism Mitchell A. Lazar and Marine Adlanmerini, a postdoctoral researcher in Lazar’s lab.

“When the external world doesn’t match the internal body’s cycles, metabolism pays the price,” Lazar told Penn Medicine News. 

Lazar and his team conducted the study after observing that shift workers — those who work long hours, overnight, or with irregular rest periods — tend to gain weight, which puts them at a greater risk of developing diabetes and other metabolic diseases.

For the study, researchers created a "mismatch" between mice's internal clocks and schedules by removing a molecule that controlled the body's internal clock and kept it to 24 hours, Penn Medicine News reported. The adjustment made the mice's internal clock about three hours shorter. 

The mice that were kept in a typical 24 hour cycle were able to keep their weight under control on their normal diet, but gained weight and developed adverse conditions when given a high fat and sugar diet, similar to the standard American diet. The control mice, which unchanged brains, did not have the same amount of poor outcomes. 

Researchers corrected this circadian mismatch by adjusting the mice’s “day” in the lab to be 21 hours, with 10.5 hours each of light and dark, Penn Medicine News reported. Once the internal clock was lined up with the length of day, metabolism seemed to return to its normal rate and the mice with the altered clocks were no longer as susceptible to the negative effects of a poor diet. 

The study's data can benefit Penn employees, as Penn's campus operates 24 hours a day and employs numerous shift workers, including security guards and sometimes students. 

To avoid the adverse effects of a poor diet, Lazar told Penn Medicine News that shift workers can time meals to match their own internal clock. 

Moving forward, Lazar and his team hope to find biomarkers that can be tested for and used to show how a person’s internal clock is running. This information could be used to inform when people eat, similar to how blood sugar monitoring can help diabetics understand when they should take more insulin, Lazar told Penn Medicine News.