I got the same problem,not diagnose off a doc but nurse at work informed me of the narrower airway during the lung function tests at work.
It's not fun and can cause unexplained weight gain (did me), crashed out test (did me), bp irregularities (did me), increases in cholesterol (did me) and my diet was relatively clean despite all of this. I realize now after diagnosis that I have to live differently and tough it out for a while, but it's working. Sleep with cpap for one, restricted calorie diet, amped up cardio, solid weight training, good supplementation, etc....may also have to treat my test issue indefinitely....it's early on though in the process but good strides in a relatively short time. It's all good though....finally have some answers after years of not knowing what in the world was happening to me LOL.