IDK. I think a lot of fit people are pretty obsessive about their nutrition, and the whole gamut of fatty foods is associated with fat people. So I guess it bleeds over from hating fat people ---> hating what fat people eat.  Though I'm gonna be honest some of the shit that gets posted here from fats' IG does look disgusting. I just won't judge a shitlord/lady who eats it because they obv know what they're doing.