Ah, yes. This happens to me quite a lot, actually. It's called my yoga class. And my Pilates class. It's also called Soho on Saturday afternoon, when everyone's shopping. Or Nolita or the far West Village on Saturday night, when everyone's out clubbing, and there are actual models picking between the Belgian blocks to their cabs in scary heels. Or the Village on Sunday, during brunch, when all the tables are set out on the sidewalk under the sycamore & pear trees.
Since I lost weight, the service at all these places is much, much better, but I am still often the heaviest woman around.
The people in these places respond to self-confidence. I may not be a model, but I might be well-known in some other industry, and they don't know that. If you act as though you have every right to be there -- you do, of course, that's the secret -- you'll be fine. So what if I don't get attention from the Wall Street model-chasers. That's okay. My value is inherent, not comparative, and doesn't change when my setting & the crowd changes.
That said, yeah, it's fascinating to see how social norms shift from group to group. The affluent do like their women thin. It's really apparent when you're traveling through neighborhoods in NY. On Fordham Road, in the Bronx, the more commonly seen body type is not the same as the body type shown off on Madison & 75th on the Upper East Side. I wasn't surprised when I read that article about one's weight being partly determined by one's friends & the people one sees every day.