how sad that no one replied! I hope I don't upsent anyone in reviving this thread...
I practice taekwondo and absolutely love it! It's actually been the main reason why I'm trying to lose weight now. It is a fast-paced sport (there's a lot of slower styles out there, like tai chi). I am one of the largest at my dojo, there are a lot of skinny people there- they totally were almost enough to make me quit my first day. I'm glad I didn't because now I'm exactly half-way to reaching Black Belt!
Being overweight made it difficult at first (and I'll admit it still it tough, but the challenge adds to the fun). Our school requires each student to do 50 sit-ups and 35 push-ups before each class. I had a lot of trouble, especially with the push-ups, but the teacher let me start by doing girl-style ones as long as I did a few real ones too. Now I've built myself up to being able to do all 35 like anyone else
I hope you haven't given up the idea of checking out a club in your area; it's a lot of fun and you get to make some great friendships.