I do not see how her losing weight harms me or affects my self-worth. I would feel better about myself is my wife were thinner.

It will not give her more power over my behavior. If she thinks she can hold her newfound attractiveness over my head as negotiating leverage, she will be disappointed. What is she going to say "if you don't take me on a vacation, I will go back to being fat"? Then she can go ahead and eat all the Oreos she wants. I have lived with an overweight wife for 12 years. I can live with one for another 6.

If she wants to date other guys, or leave me for another guy, that is her business. I am not going to make concessions to keep her around. To the extent that her losing weight gives her more options, good for her. Let her explain to the kids that we are getting divorced because she wants to be with someone else. In a wierd way, I view that as a desirable outcome. Maybe that would be the kick in the pants I need to get my life in gear.