Here's an odd little tactic that I've used occasionally when I feel embarassed to ride because of size. It is simply to ride after dark. Sounds dorky I know, but I occasionally feel better about the ride if I do it in the dark. Nowadays, that most of my weight loss is in the books and I only have 20 or so pounds to lose until I reach goal, it's not that much of an issue, but it helped a lot.
I know ideally it would be better just to go out and ride and not be concerned what everybody else thinks, but sometimes I would just get tired of it. Fortunately in my city (El Paso) night rides are very, very pleasant even during the winter.