Unfortunately, the link between the two is poorly understood. Some scientists believe that obesity places direct pressure on the lungs, while others suggest that obesity-related inflammation exacerbates asthma.
Now, new research suggests another possible driver of asthma: fat accumulation in the lungs. Published in the European Respiratory Journal, it showed that overweight or obese people with asthma have a greater amount of fat accumulation in their airways.
This buildup of fat could have slowly changed the structure of the patients' airways, effectively raising their risk of asthma. In addition, patients with a higher body mass index (BMI) accumulated more fat in their lungs. This supports further the idea of fat accumulation as a possible driver of asthma.
Lead author John Elliot, a senior research officer at Sir Charles Gairdner Hospital in Perth, Australia, said that he and his colleagues noticed that lung samples they were studying had fatty tissues built along the walls of the airways.
To determine whether or not the fatty tissues were linked to body weight, they studied postmortem samples of airway tissue from 52 people. This includes 16 who died of asthma-related causes, 21 who had asthma but died of other causes and 15 who had no history of asthma prior to their deaths.
The researchers studied the tissue samples under a microscope and used dyes to visualize the structures of the airways. They found that fatty tissues accumulated along the airways among samples in all three groups. They then compared this data with each person's BMI.
Their analysis revealed that fat accumulation was directly proportional to BMI, meaning that those who had a higher BMI also had a higher amount of fatty tissues in the walls of their airways. Similarly, people with a low BMI had a low amount of fatty tissues along their airways.
Elliot and his colleagues suggested that the fatty tissues could have altered the normal structure of the airways, creating inflammation in the lungs and significantly increasing the risk of asthma.
Additionally, the fatty tissues might have limited airflow as well. This might explain the prevalence of asthma-related symptoms in people with obesity, said co-author Peter Noble, an associate professor at the University of Western Australia.
While inconclusive, these findings suggest that weight loss therapies might just help lower asthma risk, as well as ease asthma-related symptoms in overweight or obese people. The next step now is to conduct more studies to confirm these findings.
In the meantime, healthcare professionals should encourage their patients with asthma to maintain a healthy weight, said Thierry Troosters, president of the European Respiratory Society (ERS) who was not involved in the study.
Over the last few decades, scientists have become more accepting of the idea that obesity and asthma are tied to each other, thanks in large part to numerous studies on the subject.
In fact, obesity rates are now higher among people with asthma, according to the Centers for Disease Control and Prevention (CDC). Asthma is also becoming more prevalent among overweight or obese individuals.
While scientists are moving at a snail's pace when it comes to understanding the cellular mechanisms driving the two together, existing studies and emerging research offer invaluable insight as to why these two diseases are somehow connected to each other.
For instance, a 2018 study published in Pediatrics found that obesity is a major but preventable risk factor for pediatric asthma. The study, which included a little more than 500,000 children, showed that those who were overweight had an eight to 17 percent greater risk of asthma compared to children with a healthy weight.
Furthermore, an estimated 23–27 percent of new asthma cases in children with obesity can be directly traced to obesity. Children with obesity also faced a 26–38 percent greater risk of asthma.
Meanwhile, another 2018 report showed that both children and adults with obesity are more likely to develop severe asthma than peers with a healthy weight.
While the link between obesity and asthma still warrants closer examination, existing studies thus far bring researchers a step closer to understanding how obesity and asthma affect each other's development, as well as how either disease can be prevented. (Related: Natural and effective remedies for asthma.)
Learn more about obesity and other risk factors for asthma at Health.news.