BYU study finds diesel exhaust can contribute to poor metabolism, weight gain

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PROVO — Most people understand diets full of fatty foods can affect people's health, but a new BYU study has found diesel exhaust can also contribute to metabolic diseases.

The study, published in the International Journal of Molecular Sciences, found exhaust gas produced by diesel engines is tied to increased fat mass, enlarged fat cells, insulin resistance and inflammation. These changes can lead to metabolic conditions such as obesity, diabetes and heart diseases, a release from BYU says.

"Two items have become increasingly clear to us: There are noncaloric influences on body fat, and inhaled pollution is one of them," said cell biology professor Benjamin Bikman.

Bikman, along with two professors and eight students, conducted the study to find the causal variables and learn what was occurring to the body on the fat cell level. The group studied contributing factors to metabolic disorders and observed a correlation between the global increase in obesity and air pollutant exposure.

The researchers divided lab mice into two groups for a six-week experiment where one group breathed in room air and the other breathed in diesel exhaust particles for 30 minutes a day, five days a week. Adipose tissue, or body fat tissue, was then collected from the mice for analysis.

"The rodent exposure in this study is a physiologic dose that is within the range of what might typically be experienced by humans in highly polluted areas," professor Paul Reynolds said.

The research helped the team understand more deeply how particulate matter affects metabolic function. The adipose tissue of mice exposed to diesel exhaust increased in size of fat cells, which is associated with insulin resistance and inflammation.

"While most people focus on fat mass, it's actually the excessive enlargement of fat cells that leads to metabolic issues," the researchers explained in the release.

Mice exposed to exhaust also increased in visceral fat, or fat surrounding organs, and subcutaneous fat, fat under the skin.

Lastly, researchers found that the mice also developed systemic inflammation as the adipose tissue responded to pollution by releasing chemicals to cause inflammation. This can lead to heart disease, Type 2 diabetes and autoimmune disorders.

Bikman said the findings add to the "complexity of body fat struggles" and can help show variables beyond diet that need to be part of a larger strategy to improve metabolic health.

"For so long we've considered being overweight and obesity strictly a function of overeating; the fat cell is more complicated than a caloric ATM," he said. "As much as we're mindful of what goes in our stomachs when it comes to weight management, we should be increasingly mindful of what comes into our lungs."

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Cassidy Wixom

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Cassidy Wixom is an award-winning reporter for KSL.com. She covers Utah County communities and breaking news. Cassidy graduated from BYU before joining KSL in 2022.