Losing attraction

Ok so this problem is about my girlfriend who I have been dating for five years, and I want to make it clear that I love her very much. The problem is that I feel I'm starting to lose my attraction to her. I don't think I'm a shallow person, and I'm not the most in shape guy myself, but I'll try to explain what I mean. My girlfriend is around 5ft 2, and when we first started dating was around 140lbs. Since then she's gained almost 30lbs, and it's not so much her weight but I feel I'm starting to become unattracted to her. She eats a lot, and very unhealthy food. She's always had a healthy appetite but it feels like lately she just doesn't care what she eats. We'll go for date nights and it's always an "excuse not to worry about it" and she'll order huge quantities of food. I'm talking to the point where she'll be in the car, with the seat reclined and groaning that she ate too much. I'm not someone who expects a girl to just have a salad and a water on a date, but she regularly eats so much she feels sick. Anyway, the other day I came home from work and it was her day off. She was just sitting on the couch eating a big bucket of KFC, in sweatpants, with grease all over her face. I went into our bedroom and saw an old picture of us and caught myself thinking "man, she USED TO BE so hot". I've tried doing exercise with her but she just stops and complains, and when I've tried cooking healthy meals for the two of us she just ends up snacking on other things. She told me her Mom used to make comments about her being fat (when she wasn't!) so I don't want to do anything like that, but I feel she has an unhealthy relationship with food. My conscience tells me that's an issue I need to help her work through, and I really am trying. But when I see her on the couch scarfing junk food almost every day, or feel her clothes cutting into big fat rolls when we cuddle, I must shamefully admit I cringe a little bit.

Do you ever think that maybe there is something else going on behind her eating habits? Is there something she's unhappy with in life but is perhaps too ashamed of scared to talk to you about? See if you can talk to her and find out if there is any thing at all on her mind that might explain a bit more about why she is eating the way she is.