Wow, sounds like you're in a similar boat as me. Let me give a tiny bit of background:
Currently with my wife whom I've been with for 11 years. Met her when she was 17, fell head over heels for her personality almost immediately (as she did for me) but obviously initially started talking to her because of her looks. Well, over time, she gained a lot of weight and officially one day crossed the line of no longer being attractive to me. Then, the little things about her that would irk me started to become bigger deals, simply because I wasn't as distracted by her looks anymore. To make a VERY VERY VERY long and complicated story short, this snowballed and got worse and worse. Recently, it hit its worst point, and we have come very close to ending our relationship. She finally has started to come around and realize the importance of maintaining a healthy weight and appearance, and also why its so important to me, her husband, and also her marriage in general. We've had a lot of constructive talks about it, and she's now on a fruitful path, eating very well, exercising, staying active, and even started going to an intense exercise class 4, sometimes 5 days a week. I never thought I'd see the day, but she's starting to trim down!! And she's super motivated too!! We went shopping the other day for new clothes for her because her current clothes are literally falling off of her. We were even able to buy her some items of clothes in size "S" which was extremely motivating for her.
After the talks we've had, and the information she has gathered for herself (this process took ~5 years...) she is now on the same page of understanding that if she doesn't do this, not only will her health deteriorate to a point where she can't enjoy her life anymore (pretty much already reached that), but also that it would be completely and totally fair if I ended our marriage. It would suck a lot for ME because I didn't do anything wrong, I was a good partner for 11 years, and now at age 31 I'd have to hit the dating pool again, but you gotta enjoy your life. Now DON'T GET ME WRONG, she's not doing this FOR ME, I simply spoke about my own perspectives in this post because I'm trying to relate to your situation. SHE needs to want to do it for HERSELF, and all you can do is be encouraging and supportive, no matter how frustrating it is.
The bottom line is you need to ask yourself how much you are IN LOVE with this woman, and how worth it she would be for you to stick it through, go through what I explained above, and HOPEFULLY come out on the other side feeling attracted to her again. However, you also need to draw a line where enough is enough, and this needs to be communicated to her. She's gotta realize the importance physical attraction in a relationship, especially for the man. You better be keeping yourself trim too though! Don't be a couch captain!!
It's up to you man, but personally, I know that I would miss my wife terrrrrrrrrrrrrrribly if I left her. I love her more than anything, she's the woman for me, and I want nothing more than to just have her be healthy and happy.
Good luck man.