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Study finds fat builds up in lungs of overweight and obese people

By Jess Glass, PA

A study has found the first evidence that fat accumulates in the lungs and airways, particularly in overweight and obese people.

It was previously known that people with higher body mass indexes (BMIs) were at a greater risk of suffering from wheezing and asthma, with higher rates of severe asthma.

Researchers based in Australia have now suggested that fat deposits narrowing the airways could be a reason behind this previously unexplained increased risk.

The peer-review study published in the European Respiratory Journal, which is thought to be the first of its kind, found that excess fatty tissue changes the structure of people's airways.

Researchers from Sir Charles Gairdner Hospital, Perth, and the University of Western Australia used samples from 52 people and examined 1,373 airways.

They looked at the lungs of people who had died from asthma, as well as asthma sufferers who had died from other causes and a group of those without asthma to evaluate the impact of BMI on the airways.

Using the tissue samples and dyes, they microscopically examined the amount of fat in the lung tissue and compared that with the person's BMI and medical history.

The researchers discovered a correlation between the amount of fat in the lungs and body weight.

It was known that fat accumulates around other organs including the liver, but there had previously been no research into the impact of excess fat on the airways.

Dr Peter Noble, associate professor at the University of Western Australia in Perth and co-author of the study, said: "Being overweight or obese has already been linked to having asthma or having worse asthma symptoms. Researchers have suggested that the link might be explained by the direct pressure of excess weight on the lungs or by a general increase in inflammation created by excess weight.

"This study suggests that another mechanism is also at play. 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."

There are now hopes that this initial finding will now lead to further studies on the relationship between asthma and high BMIs as well as research into whether the effects can be reversed by weight loss.

European Respiratory Society president Professor Thierry Troosters, who was not involved in the study, 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.

"This goes beyond the simple observation that patients with obesity need to breathe more with activity and exercise hence adding to their ventilatory burden. The observation points at true airway changes that are associated with obesity."