Obese people may have dangerous amounts of fat in their lungs, research suggests.
Scientists from the University of Western Australia analysed lung samples from 52 people post-mortem.
They found the amount of fat in the vital organ increased alongside the deceaseds’ BMI.
Fatty tissue may “take up space” in the airways, causing them to narrow, the scientists warn. It could also trigger inflammation, a tell-tale sign of asthma.
Asthma is known to be more common in obese people, with 16 of the participants dying of the disease.
“Being overweight or obese has already been linked to having asthma or having worse asthma symptoms,” study author Dr Peter Noble said.
Experts have blamed this on the increased pressure on the lungs, as well as obese people having higher levels of inflammation in their bodies in general.
“This study suggests another mechanism is also at play,” Dr Noble said. “We’ve found 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.”
How many people are obsese - and what are the implications?
In England alone, 29% of adults are obese, NHS Digital statistics show.
And in the US, 39.8% of Americans were dangerously overweight in 2015/16, according to the Centers for Disease Control and Prevention (CDC).
Obesity has been linked to everything from type 2 diabetes and heart disease to depression and even some cancers.
It is also associated with the onset of asthma, as well as worse symptoms and poor disease control.
Some 5.4 million people in the UK are being treated for asthma, with three people dying from the common condition every day, Asthma UK statistics show.
In the US, 19.2 million adults and 5.5 million children battle wheezing, breathlessness and incessant coughing, according to the CDC.
To better understand the link between obesity and asthma, the scientists analysed almost 1,400 lung tissue samples that had been donated for research. The deceaseds’ BMIs ranged from underweight to severely overweight.
Sixteen died from asthma, while 21 had the inflammatory lung condition but passed away of another cause. The remaining 15 had not been diagnosed with the disorder.
Results, published in the European Respiratory Journal, showed those of a higher BMI had greater levels of fatty tissue in their airways.
They also had more of the cells neutrophils and eosinophils. These fight infections and are associated with inflammation.
It is unclear whether losing weight could reverse the damage.
Professor Thierry Troosters, president of the European Respiratory Society, said: “This is an important finding on the relationship between body weight and respiratory disease because it shows how being overweight or obese might be making symptoms worse for people with asthma.
“We need to investigate this finding in more detail and particularly whether this phenomenon can be reversed with weight loss.
"In the meantime, we should support asthma patients to help them achieve or maintain a healthy weight."
With obesity on the rise worldwide, one expert hailed the study “of major importance” but added further research is required.
"Given the increasing incidence of obesity nationally and across the globe, the study could be of major importance in helping us understand why asthma remains a major health issue and identify new ways to improve asthma treatment," Dr Elizabeth Sapey, respiratory consultant physician at the Queen Elizabeth Hospital in Birmingham, told the BBC.
"It is only a small study though, and we need to assess this in larger groups of patients and in other lung diseases.”