The diverse effects of obesity on lung health and disease are increasingly being teased apart, with researchers honing in on the impact of metabolic dysfunction, circulating inflammatory factors produced by adipose tissue, lipid handling, and other factors – in addition to body mass index – that are associated with the obese state.
“The bird’s eye view is that obesity completely changes lung health. It’s something we’ve only recently begun to appreciate,” said Anne E. Dixon, MA, BM, BCh, director of the Vermont Lung Center at the University of Vermont, Burlington, who is focused on the research field of obesity and lung disease.
Dr. Anne E. Dixon
Structural, mechanical effects of obesity on lung function are better known and appreciated. Accumulation of fat in the mediastinum and abdominal and thoracic cavities causes reductions in lung volume, in functional residual capacity, and in the compliance of the lungs, chest wall, and entire respiratory system, for instance.
Yet obesity is more than a state of increased BMI, and “what we’ve begun to understand is that [its impact on the lungs and respiratory health] is much more complicated than just a mechanical problem,” said Dr. Dixon, also director of pulmonary and critical care medicine at the University of Vermont Medical Center and professor of medicine at the medical college.
With obesity, adipose tissue changes not only in quantity, but in function, producing proinflammatory cytokines and hormones – such as leptin, tumor necrosis factor-alpha (TNF-alpha), and interleukin-6 – that can have direct effects on the lung. Insulin resistance, which is common with obesity, is also seemingly deleterious. And obesity-associated changes in immune function, lipid handling, diet, and the gut microbiome may also impact lung health and disease, she said.
Dr. Dixon, who wrote about these changes in a 2018 review article in the journal CHEST and another 2019 piece in Expert Review of Respiratory Medicine, has developed a research program focused on obesity and lung disease and has edited a book and organized international conferences on the topic. (CHEST 2018;153[3]:702-9 and Exper Rev Respir Med. 2018;12[9]:755-67.)
“The more I do, the more I realize that there are multiple obesity-associated changes involved, and that [our current high level of] obesity is like a huge population-level natural experiment ... on lung health,” she told this news organization.
Associations between lung disease and the metabolic and other disturbances of obesity are most established in asthma research and have taken hold in the realm of sleep-disordered breathing. But as the prevalence of obesity continues to grow, its role in other lung diseases such as chronic obstructive pulmonary disorder (COPD) and, most recently, pulmonary arterial hypertension (PAH), is getting attention in academia.
And certainly, COVID-19 has highlighted an “urgent need” to better understand how obesity increases susceptibility to severe viral infections, Dr. Dixon added.
Here are some glimpses into current thinking and some examples of research that may have preventive and therapeutic implications in the future: