My question–are most of your friends fat or thin? Do you find “fat” to be common ground?
Not currently. Most of my local friends are average-sized. (Of course, most people are average-sized. I think it’s a math thing. :) They may be technically / clinically overweight or obese, but they’re at the size where people will tell them “Oh, you’re not fat”. I also have friends who are thin, including a few who get accused of anorexia, and friends who are fat. I’m married to someone who wears men’s 3X.
I don’t have any local friends who are bigger than me, but I have some long-distance ones who are.
I would add that I done the “find a fellow fat friend” thing, most notably in middle & high school.
I have dated people who are fat and thin, but that is skewed a bit more to the fat side – most of my lovers have been at least clinically overweight or obese.