Others have said it pretty well already but I think it boils down to a few things:
- Various perceptions of what fat looks like to people. I liked the link kelly posted and was surprised by my own reactions. I'd look at the picture and then try to guess where they were. Most of the time I was pretty accurate but there were a few times that I was shocked that someone was considered overweight/obese and would've thought that they were a category down from where they were. There were actually one or two times that I was surprised somebody was listed as normal because I thought they were overweight. And there was also one girl who I was really surprised was underweight. This is coming from someone who's lost weight and has been in all those categories (with the exception of underweight) so I agree it really is hard to tell.
- It's also somewhat of an automatic comment. Like Kaploids and others said too, fat can be considered a "bad" word so others like you as a person and wouldn't want to associate that with you or like Lovely said that they may think you're feeling down about yourself and just want to cheer you up.
- I could be insecurities too but I don't like to assume that in general. I like to think the best of people and it seems sort of devious to think that everyone wants you to eat more so they feel better about themselves. It
could be the case but I think to think that it's rare.
- And, of course, I think the gradient is SO important. Just watch a season of biggest loser! I remember having a hard time believing some of the contestants are still in the 200's because I remember how they looked in the beginning and they look so different later on that your mind wants to believe they are already at a healthy weight. It's just hard to reconcile the images in your head.