rpearso3,
I also have asthma and 2 years ago weighed the same as you (at 6'1'') I do not have the same joint problems as you, but thanks to years of martial arts they are on their way out.
If you want to lose weight fast but safely, i recommend that you lower your intake of carbohydrates and sugars and combine that with drinking a lot of water (over 4 litres a day at least) and swim as much as you can possibly bare. Remember, the pain brings gains... cheesy but true. The amount of cardiovascular torture you put yourself through will directly correlate to the amount of progress you make in losing excess weight.
Also, heavy lifting has been shown to aid fat loss especially when combined with cardiovascular training.
Good luck man, you can definately do it.
Remember to consult with your healthcare provider before embarking on a new excersise regime.
hi there-do you live near a "Y" or have access to a pool? I know water exercises are easy on the joints
I forgot to say, I'm 5'10" and about 215 pounds.