I dont think you can say 'most' people. I would never do it, neither would any of my close friends or my DH. I think it is exceptionally cruel and rude to mock people about their appearance full stop.
But yes, its is still socially acceptable in some arenas. You only have to open up a womens mag or tabloid to see pictures of not-even-that-fat women being ridiculed and criticised for their weight.