Obesity and asthma are both serious health problems that many people in the U.S. face. Unfortunately, many people have to manage both at the same time. Research shows about 60% of people with asthma are also obese (have a BMI of 30 or higher). These numbers are increasing, with studies supporting that people with asthma are 75% more likely to become obese than those without asthma. Having both obesity and asthma can lead to worse health outcomes because people with both conditions often have more severe asthma that is harder to control. They may also have other health issues like depression or sleep problems, which can put a strain on disease management.
“Being overweight or obese can complicate asthma symptoms, and asthma treatment drugs have been shown to be less efficient for people who are obese,” said Ian Saldanha, PhD, MPH, MBBS, from Johns Hopkins Bloomberg School of Public Health.
Many new weight-loss drugs are now flooding the market, including medications like liraglutide, metformin, semaglutide and others. But little is understood about how these drugs may affect the respiratory system, especially for people with asthma. “New weight loss drugs are promising, but we need to understand the potential harms or effects of these new drugs on the respiratory system.” It is this subject that interests Dr. Saldanha and his research assistant, fourth year epidemiology PhD candidate Lijuan Zeng.
Analyzing Data for Answers
Dr. Saldanha’s team is concerned with answering two main questions:
- Regardless of asthma status, what are the respiratory harms of these weight-loss drugs compared with other weight-loss drugs or no weight-loss drugs?
- And, in patients with asthma, what are the effectiveness and harms of weight-loss drugs compared with other weight-loss drugs or no weight-loss drugs?
Although primary studies enroll patients, Dr. Saldanha decided to take a different approach. Over the last few years, he and his team sifted through thousands of studies in a systematic review. This method allowed the team to conduct a rigorous, unbiased comprehensive evaluation that considered the findings of all relevant studies about asthma and weight-loss drugs that they could find.
“This method (systematic review) has evolved over the last 20 to30 years and is widely and increasingly used to underpin clinical practice guidelines,” Dr. Saldanha explained. “We ran a search of multiple databases and began with about 9,000 records. Then, we went through to find the ones that were relevant. We ended up with 123 studies that addressed one or the research questions.”
This was not an easy task as very little research has been done on people with asthma and weight loss drugs. “While we know that losing weight can help improve asthma control, we know of only a few small studies that have tested weight-loss drugs in people with asthma,” Dr. Saldanha said. “For example, two small trials funded by the National Institutes of Health (called PLAN and TRIM) found that losing about 5% of body weight might help with asthma. But those studies were limited to about 40 participants, and one of the drugs used (roflumilast) caused side effects in some participants.”
Many other studies may have been useful but unfortunately, if the researchers didn’t ask questions about respiratory harms, participants rarely reported them. The data they were able to analyze, however, showed a clear pattern. There is strong evidence that the weight loss drugs do not increase the risk of respiratory harm.
“There was no signal that the drug was causing more risk of respiratory harms,” said Lijuan Zeng. “The risk was generally low and was consistent for all groups. Upper respiratory tract infections, or nasopharyngitis, were present in some patients, but these effects also occurred in patients who received a placebo.” This is promising as, if these drugs are not associated with much harm to the respiratory system, they can help those with asthma lose weight which may improve their asthma symptoms and lead to better overall health.
Understanding the importance of weight loss for the general public, especially for those with asthma, Dr. Saldanha’s research will continue to explore how asthma and weight loss drugs may interact. Learn more about his research and other asthma research on our Clinical Trials page.
Blog last updated: May 23, 2025
