Yeah I think a lot of people just dont know what to say when it comes to weight and really dont realize when to keep their mouth shut. I've learned to laugh it off. People who have never been significantly overweight just genuinely don't "get it" and probably dont even realize how their comments could be interpreted. My bet is they were trying to be supportive and it came out wrong lol.
I know what you mean about the eye flick, Shmead, it makes me downright uncomfortable. Particularly when it comes from a shop assistant as you're trying on clothes