Patient Encounter: Can Obesity Cause Asthma?
I saw a patient two weeks ago with asthma who asked me an important question: “Is my obesity making my asthma worse?”
I explained that while obesity definitely contributes to shortness of breath in asthmatics, and that asthma control improves with weight loss, we are not sure whether obesity directly causes asthma. And there are some scientists who believe that people who are obese are at greater risk for worse swelling and inflammation in the bronchi (windpipes), leading to more wheezing. I reviewed her asthma medications with her and spent a few minutes reviewing the importance of weight control on overall health as well as controlling asthma symptoms.
Here’s some more background information on the obesity-asthma connection. Obesity is defined by one’s body mass index (BMI). BMI is calculated by dividing weight in kilograms by the square of height in meters:
Body Mass Index
An ideal BMI is between 20 and 25 - for example, a 65 kg person (143 pounds) who is 5 foot 8 inches tall (1.73 meters) has a BMI of 22. A BMI of greater than 30 defines obesity; the percentage of Americans who are obese has increased to about 20% from 12% in the last twenty years.
This trend has been accompanied by an increase in the percentage of Americans who have asthma, and scientists have looked for a link between the two. It is clear from this research that people who are obese have more asthma than those who are not.
There are several ways in which obesity may worsen the risk and severity of asthma: breathing mechanics (how easy or hard it is to get air in and out of our lungs) are altered, obese individuals may be more prone to inflammation in the lungs, and problems in dosing medicines accurately. There is also good evidence that weight loss (especially after weight reduction surgery) leads to much better control of asthma symptoms. Nevertheless, while obesity is associated with asthma, we do not know if, or how, obesity directly causes asthma.
Whether obesity causes asthma or not, it is directly associated with several other health problems, such as diabetes and high blood pressure. The BMI is easy to calculate - anyone with a BMI greater than 30 should look for ways to decrease this - whether they have asthma or not. Overall health and lung health are directly connected.
Published On: June 27, 2006