A new study has found that fatty tissue can
accumulate in the airways of people with obesity, possibly contributing to
asthma and other respiratory problems.
In
the United States, as well as across the world, obesity has
become a top health issue. According to data cited by the National Institute of
Diabetes and Digestive and Kidney Diseases, in the U.S. alone, more than one in three adults have
obesity.
While
this condition is associated with a heightened risk for many other health
problems, it is unclear through which mechanisms it contributes to some of
these issues.
One
such mysterious link is that between obesity and asthma. Although researchers have provided different explanations for it, how obesity
contributes to respiratory problems remains unclear.
Now
a study whose results appear in the European
Respiratory Journal shows that fatty tissue can accumulate
in the airway walls. It explains how this may be problematic for people who are
overweight or who have obesity, as it may contribute to the development of
respiratory conditions, such as asthma.
"Our
research team studies the structure of the airways within our lungs and how
these are altered in people with respiratory disease," explains first
author John Elliot, from Sir Charles Gairdner Hospital in Perth, Australia.
"Looking
at samples of lung, we spotted fatty tissue that had built up in the airway
walls. We wanted to see if this accumulation was correlated with body weight,"
he continues.
'Excess fat accumulates in the airway walls'
To
do this, the researchers analyzed lung samples collected post-mortem from 52
lungs that people had donated for research. Of this total, 15 had not had
asthma, 21 had had asthma but died due to unrelated causes, and 16 had died due
to asthma-related causes.
The
investigators used special dyes to study the structure of 1,373 airways to
identify how much, if any, fatty tissue was present in them. The researchers
also looked at data regarding each donor's body mass index (BMI).
The
team discovered that fatty tissue does build up in airway walls. They also
found that the higher a person's BMI, the more fat accumulates in the airways.
Additionally,
the fat buildup may affect the normal structure of the airways, blocking them
and causing inflammation in
the lungs, which, in turn, may contribute to asthma and other respiratory
problems.
"Being
overweight or obese has already been linked to having asthma or having worse
asthma symptoms," notes co-author Peter Noble, Ph.D.
"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," he says.
"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."
Peter Noble, Ph.D.
Going
forward, the researchers hope to confirm the relationship between obesity,
fatty tissue in the respiratory system, and pulmonary health problems. They are
also interested in finding out whether weight loss could reverse the potential
impact of obesity on respiratory health.
Prof.
Thierry Troosters — President of the European Respiratory Society, who did not
participate in the present study — comments on the researchers' discovery. He
says that "[t]his 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," he emphasizes.
Prof.
Troosters acknowledges that further research is needed to understand the
association between obesity and poor respiratory health better. However, he
also encourages individuals with asthma or similar conditions to keep a close
eye on their weight.
"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," he
says.
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