Obesity and Asthma – Does Obesity Worsen Asthma?

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Obesity is associated with increased risks for many serious illnesses, such as diabetes, high blood pressure, arthritis, and some kinds of cancer. It is often also found in association with asthma. As rates of both asthma and obesity have skyrocketed in recent years, scientists wondered whether the link was more than coincidence.

For instance, one study found that nearly 75 percent of patients who visited emergency rooms for asthma-related complaints were also obese. As Jeffrey Fredberg of the Harvard School of Public Health noted, "Obesity has the capacity to impact lung function in a variety of ways. None of them are good and all of them are poorly understood. More research is needed to explain the relationship between asthma and obesity."

Obesity Worsens Asthma - A Misconception?

Self-reported data from patients themselves supported the theory that people who are obese are more likely to develop asthma, and that when they do, their asthma is likely to be more severe. A 2008 research study conducted by researchers from Harvard Medical School, Massachusetts General Hospital, and Kaiser Permanente looked at 1,113 adults with asthma and found that obese asthmatics were almost five times likelier to be hospitalized for the problem and reported lower quality of life and less success managing their asthma.

Another group of researchers at the National Jewish Medical and Research Center and the University of Colorado in Denver, CO, recently set out to look at this question using less subjective data. Their findings appeared in the June 2009 issue of the Journal of Allergy and Clinical Immunology. They studied the records of 1,256 patients with asthma, separated into two groups according to body mass index—BMI under 25 (lean) and over 25 (overweight/obese). The leaner patients showed slightly better lung function in two areas, while overweight patients showed a slightly greater reliance on rescue inhalers. But "These differences were small and are unlikely to be of any real clinical significance," according to lead author Dr. E. Rand Sutherland, Associate Professor of Medicine at National Jewish Health.

Dr. Sutherland concludes, "we were able to determine that increased weight is not associated with more severe asthma. Although benefits can be obtained with weight loss in other diseases, these findings suggest that an improvement in asthma may not necessarily result from weight loss."

Medicines For Asthma Less Effective For Overweight Patients

But the researchers did uncover one significant interaction between asthma and obesity that has implications for asthma treatment. In the group of patients under review, they found that the corticosteroid medicines most commonly recommended for controlling asthma were much less effective for overweight patients. “Obese asthma patients may not respond well to corticosteroids, the most successful controller medication for asthma, which can affect dosing decisions and choices of possible alternatives to steroids."

An abstract of the Denver study, “Body mass index and phenotype in subjects with mild-to-moderate persistent asthma,” by E. Rand Sutherland, Erik B. Lehman, Mihaela Teodorescu, Michael E. Wechsler, National Heart, Lung, and Blood Institute's Asthma Clinical Research Network, along with links to the full text (subscribers only), is available at:

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