It's no secret that many Americans struggle with their weight. If you're one of them, you're not alone. According to the Centers for Disease Control and Prevention (CDC), 38 percent of adults in the U.S. are obese, defined as having a body mass index, or BMI, of 30 or more (the normal range is 18.5-24.9, and overweight is 25-29.9). This is not just a problem for adults of course, it's also a problem for children: around 21 percent of kids between the ages of 12 and 19 years old are also dealing with obesity.
Why is this relevant to people with asthma?
People with a BMI of 30 or more have a much higher risk of having asthma than those with a lower BMI. Seven percent of adults with a BMI in the normal range have asthma but 11 percent of adults with a BMI classified as obese have asthma. And, for reasons we don't yet understand, this seems particularly a problem for women - nearly 15 percent of women who are obese suffer from asthma.
It's not entirely clear why carrying extra weight should cause asthma. Certainly extra weight around the chest and abdomen might constrict the lungs and make it more difficult to breathe. It's probably a lot more complicated than that though. Fat tissue produces inflammatory substances that might affect the lungs and a number of studies have suggested that these substances affect asthma.
What we do know is that obese patients often use more medications, suffer worse symptoms and are less able to control their asthma than patients in a healthy weight range.
Research performed by the American Lung Association Airways Clinical Research Centers Network (ACRC) —the nation's largest not-for-profit network of clinical research centers dedicated to asthma and chronic obstructive pulmonary disease (COPD) —has shown that people with asthma and a BMI over 30 do not respond in the same way to medications as people with a lower BMI. Obese people with asthma have worse asthma control when treated with theophylline, a drug used in therapy for asthma that relaxes bronchial smooth muscle. Other research groups have reported that obesity reduces the effectiveness of medications like inhaled corticosteroids.
Another problem identified in ACRC research is that people suffering with both obesity and asthma more often have other medical problems that might affect asthma. People with a BMI over 30 tend to have depression more often than leaner people and depression is associated with worse asthma symptoms. Another medical problem that is more common in overweight or obese people is obstructive sleep apnea. People with obstructive sleep apnea and asthma also appear to have more severe asthma symptoms than people with asthma without obstructive sleep apnea.
Extra weight increases the risk of having asthma and having more severe, difficult to control asthma. So what's the solution? Losing weight can be hard for anybody and might be particularly challenging if asthma makes it difficult to exercise. The ACRC is hoping to research ways that might help people with asthma lose weight. In the meantime, eating a healthy diet and avoiding a lot of fat in your diet might be helpful. Some research suggests that eating food high in fat worsens airway inflammation in people with asthma. Walk more, try to get some exercise every day – it will help your weight and it will also help you breathe.