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Fat may alter the structure of the airways and lead to inflammation in the lungs. Getty Images
  • People with overweight or obesity are more likely to experience asthma or wheezing.
  • Now a new study finds that fat deposits may appear in the airway walls of the lung.
  • Fat may be able to alter the structure of the airways.

Fat can get into the airway walls of the lungs and alter their structure, which may be the cause of wheezing, asthma, or both, a new study suggests.

People with overweight or obesity are more likely to experience asthma or wheezing, but scientists weren’t exactly sure why.

The study published this month in European Respiratory Journal suggests that fat deposits could have similar effects of artery plaque, which can clog vessels and cause cardiac events.

A team based in Australia found that fat can accumulate in the airway walls, particularly in people with overweight or obesity. They believe this could be why those with overweight or obesity have a higher risk for asthma.

The researchers examined postmortem samples of lungs from 52 people. Of them, 16 died of asthma, 15 didn’t have asthma, and 21 had asthma but died from other causes.

The scientists inserted dyes into the lung tissue and examined the structures of 1,373 airways, then correlated the fatty tissue with the body mass index (BMI) of each individual.

The amount of fat increased in line with BMI, they found.

Fat may alter the structure of the airways, and may lead to inflammation in the lungs, they also noted.

Peter Noble, PhD, co-author and associate professor at the University of Western Australia in Perth, says that research has suggested the link between higher weight and asthma could be a result of pressure from excess weight on the lungs, or it could be due to a general increase in inflammation.

“We’ve found that excess fat accumulates in the airway walls where it takes up space and seems to increase inflammation within the lungs. We think this is causing a thickening of the airways that limits the flow of air in and out of the lungs, and that could at least partly explain an increase in asthma symptoms,” he said.

The team was most surprised that the amount of “fat” in the airways was related to wall thickness, Noble says. This is a common feature in diseases like asthma.

“From this we speculated that airway-associated fat may contribute to the increased severity of disease in individuals who have asthma and are also overweight,” he added.

Fat cells are known to be pro-inflammatory, so excess weight likely causes systemic inflammation, Noble explains.

The study didn’t provide enough data to explain exactly how fat gets into the lungs.

“Fat will distribute throughout the body in spaces that can accommodate increased fat mass,” Noble told Healthline. “Poor diet and lack of energy expenditure with exercise avoidance likely contributes to airway-associated fat, as it does in other biological tissues. Our study suggests that if you are overweight, you are more likely to have fat in the airway wall.”

But it may not be that simple, as some people who don’t have overweight or obesity can have fat around their organs, Noble adds.

The researchers plan to study their results further, and want to know whether weight loss can reverse respiratory symptoms.

Dr. Albert A. Rizzo, chief medical officer at the American Lung Association, who wasn’t involved with the research, says the study is an “important first step” in correlating the appearance of increased fat deposits in the airways with the presence and severity of asthma in those who have overweight or obesity as well as asthma.

More research needs to be done using other techniques to measure fatty tissue in the lungs and how it correlates in people who are living with asthma, Rizzo says.

The medical community knows that airway responsiveness seems worse in people with obesity and asthma compared with people who don’t have those conditions. That may be because chemicals known as adipokines are elevated in the former. Weight may play a role in asthma independently as well, Rizzo says.

“Further evidence for the relationship between obesity and asthma is being seen in the actual makeup of the airway walls with evidence of fat deposits,” Rizzo added.

But that doesn’t solely explain the relationship between obesity and asthma.

“It is now recognized that there is obesity associated with early onset allergic type asthma as well as obesity that occurs in late-onset nonallergic asthma,” he added.

Pulmonary fibrosis is a lung disease that causes scarred, stiff tissue within the lungs. A 2015 study found higher levels of fat in the lungs of people with the disease.

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