I bring up our lack of knowledge because it can often come as a surprise when something which was long accepted to be true is proven not to be. Our history is littered with these once-facts which get cast out with superior reason, research or simply observation. It’s important to understand that medicine, just like science is never truly a static organism. It’s always advancing and changing as more information or technology becomes available to us.
It’s been shown that obesity is unlikely to make mild or moderate forms of asthma worse. The two conditions have been under great scrutiny for a long period of time as they’ve both seen a huge rise recently. Though there’s a correlation between sufferers of severe asthma and their condition being much worse if they’re obese, there simply wasn’t one for people with less dangerous forms of the condition.
Researchers have argued that in actual fact losing weight will probably be beneficial to an obese asthmatic but they hastened to add that most conditions would improve with general weight loss. Most of those conditions didn’t correlate to obesity either. So losing weight won’t hurt but it won’t make your condition massively worse.
We’d still advise trying to lose a bit of weight if you can! Better to be safe than sorry.