For a while we’ve known that asthma correlates with obesity. However, it hasn’t been clear whether or not one condition causes the other. Now, a new joint study by the University of Queensland, Australia and the University of Bristol, UK claims that obesity can cause asthma.

According to one of the study’s authors, David Evans, "In the past we haven't been sure whether a high BMI [body mass index] causes asthma, or if asthma causes high BMI, or another variable entirely is responsible for both… We tested genes that we knew were related to BMI. If increased BMI were truly responsible for increased risk of asthma, then we would expect that these genes would also show a relationship with increased risk of asthma, which is exactly what we found."

The authors even believe that the rise in obesity worldwide may have contributed to the rise in asthma worldwide. However, they still don’t know why obesity would cause asthma. One theory is that the inflammation caused by obesity affects the body’s immune system and triggers asthma. But more research is needed to know for sure.

The study, which took place in the UK, looked at 5,000 asthmatic children from age 7 and up. The researchers scored the children on 32 different BMI-related variables, then assessed the connection between those variable with the children’s fat mass, lean mass, BMI, and asthma condition.

Hopefully, in the future researchers will figure out how obesity contributes to asthma, so we can better fight against it.