I always thought that fat people are fat because they are mentally ill in some way. I can't imagine being OK with being fat, and I think it reflects either depression or some other emotional incapability of loving oneself enough to want to be healthy and live a healthy life. I did all my self-destructive behaviour when I thought I wasn't deserving enough to be healthy and happy. maybe it's the same for them.
No one can be happy with being fat. I'm not saying you can't be ten pounds overweight and happy, but I am saying you cannot be grossly obese/obviously a total porker and be cool with that.
It's pretty fashionable these days to say "Real women have curves"- and this is true up to a point, but there is no sense telling someone they look good when they are literally feeding their own self-destruction.