Ok, Temp. Everyone is quick to jump down your throat here, which is easy to do.
i am just gonna give you the benefit of the doubt and assume you really want to help her do something that she seems to want to do (i.e works out a lot, has the weight loss books, etc). I think the best advice given so far has been by Lockjaw.
You really should work out with her. You will get to spend more time together and it can be good for both of you. Obviously it is something she likes to do, and I am sure she would enjoy it if you shared that part of her life with her.
She may have eaten all of her food because she is comfortable with you as well. Or she may have just been hungry. She is a very active person it seems and would need the food to keep her going. It is not a bad thing, in my opinion, at all.
As your relationship progresses, you will learn more about her. Maybe she was teased a lot and that is why she works out so much, who knows. Just be there for her. Perfection is not a societal standard. regardless, of what you think your ideal woman is, she may turn out to be perfect for you. I am not saying look past her "flaws", because they aren't flaws. That is who she is. Fall in love with that. Enjoy her. Help her to achieve her goals, whatever they may be.
I think you really care about her and want to do all this. Sorry that people assume you are insensitive to her. Its hard to bring up stuff like this through a textual medium so don't be angry with the responses either. It is just how others viewed your statement.
Best of luck man.