I was diagnosed with asthma in 2009 and was constantly breathless and wheezing and by 2012 was walking only with the aid of sticks. Also had gastritis and felt full after a mouthful of food. Was diagnosed with diabetes, I cut out the obvious carbs like bread, pasta, cakes etc and was put on Metformin in August 2012, within a few weeks the wheezing had almost disappeared and I had a bit of energy for the first time in years.
If I fall off the wagon and start eating bread and cakes again, I soon start wheezing but not to the degree I did before, because I quickly cut back on the carbs.
I do think in some case asthma can be a symptom of undiagnosed diabetes or possibly that cutting out the carbs highlights a possible intolerance to wheat that we wouldn't have known about otherwise.
I don't use any inhalers now, but I do carry my Epipen because I'm also prone to angioedema and anaphylaxis. Can't run a marathon, but can talk and walk at the same time which is a vast improvement.