Obesity and Asthma – What Weight Loss Doesn’t Help
- By Jennifer Nachbur
Each year, approximately 250,000 of new asthma cases are linked to obesity, says Anne Dixon, M.D., associate professor of medicine and director of pulmonary and critical care medicine at the University of Vermont College of Medicine. This link between obesity and asthma has been established over the past ten years, but researchers are still seeking to better treat the condition in this population. A recent study by Dixon and colleagues looked at how obesity and weight loss – or bariatric – surgery affect asthma control, airway hyperresponsiveness (AHR), and markers of asthmatic inflammation.
“Obese individuals tend to have more severe asthma, and do not respond as well to therapy,” explains Dixon. “When we started this study, we assumed that obesity would somehow make their allergic airway inflammation worse.”
While Dixon’s study showed that bariatric surgery led to dramatic improvements in asthma control, suggesting that weight loss is an important intervention, it also had another major – and unexpected – finding. She and her team learned that the type of immune reaction that typically causes asthma actually increased after the bariatric surgery.
Study participants’ airway function did not change much, implying that their previous poor asthma control was likely related to some effect of obesity worsening their symptoms, and not due to typical allergic airway inflammation.
“What we learned is very important, because it suggests that all of the first-line asthma treatments that target this type of immune response are likely to be of limited effectiveness in the obese,” Dixon says.
These research findings – that asthma in obese individuals is due to a combination of the effects of weight on airway function, and metabolic changes in fat affecting the airways – has set Dixon and colleagues on a new path to identifying a treatment for obese asthmatics.
Dixon's UVM coauthors on the study include Patrick Forgione, M.D., associate professor of surgery; David Kaminsky, M.D., associate professor of medicine; Laurie Whittaker-Leclair, M.D., associate professor of medicine; Laurianne Griffes, research coordinator, Vermont Lung Center; Jayanthi Garudathri, M.S., research/lab technician in medicine; Danielle Raymond, research technician in medicine; Mathew Poynter, Ph.D., associate professor of medicine; Janice Bunn, Ph.D., assistant professor of mathematics and statistics; and Charles Irvin, Ph.D., professor of medicine.
To read an abstract of the study, titled "Effects of obesity and bariatric surgery on airway hyperresponsiveness, asthma control, and inflammation," go to http://www.sciencedirect.com/science/article/pii/S0091674911009249 .