A real marriage transcends tit-for-tat or quid pro quo. If you really love your wife for who she is, stop looking at what she is doing. Self care is her issue to deal with. Don't be on her case. It's not going to help her or you. If she feels that you are turned off by her, part of that affects her psyche and will keep her down on herself (not attractive to anyone).
You might be a great force of inspiration for her if you work out and take care of yourself. One of you has to make the first move at some point so that each of you can lift out of the depths of your dark hole together. Since you are here, you have the distinct opportunity of knowing that it can be YOU.