If she's too thick, you have to be more direct.
It's not just what you say but HOW.
A softer way:
"Hey babe, I'm really worried about your health. Are you stressed? Can't find time to exercise because too much work? You've been putting on alot of weight, yes you have. You need to exercise and eat healthier. I'm worried about you, you haven't looked and acted like yourself in awhile."
That is so lame, it makes me want to cry.
She doesn't care about you, she doesn't care about herself. Move on, there's nothing left here. But you're not going to. Based on your replies to her you strike me as a major AFC. You can't speak your mind, you can't explain yourself and you're worried about offending.
I would go as far to say that this is all your fault. You're supposed to be the man and give your girl the support and direction she needs. She's not even happy with anything anymore, she's a mess inside and eating makes her feel good for a little while. She's asking for your support (indirectly) but you're too afraid to do anything. Hell I don't blame you though. You're weak and pathetic. Can't do anything for yourself, much less help out your girl.
Peace out.
I await the swift and brutal conclusion to this mess. Including the
"I love her, how can I win her (fat lazy ass) back?" threads.