I've been so embarrassed to ask the skinny flight attendants for one, that I've actually tucked the belt up under my tummy (so from the side it looked like I was belted in), and strategically draped a coat over me and pretended I was sleeping.
I've also purchased an extra ticket, so that I'd fit into the seat. You still get that, "I hope I don't have to sit by her" look as you get on the plane, but once you're seated you're comfortable. (I travel during the Christmas holiday and it was cheaper to buy 2 seats than to go first class.)
If I get approved for my surgery (aiming for late August) I'll probably want the extra seat this Christmas (because I have a lot to loose), but I definitely wont need it the following year!
One time I was at the Grand Canyon, and went to sign-up for the mule ride into the canyon. I was dismissively told by some thin college kid, that there was a 2 year waiting list, to ride into the canyon. Then he added, "Besides you have to be under 200 pounds, fully dress and including your gear". I was about 175-180 at the time, so I started to say something and he interrupted me to say, "They will weigh you".
I just walked away feeling humiliated.