Building on what Roadwarrior and some other have said…
o Get off of her back! Nothing makes you chow down on tubs of ice cream like someone telling you that your dietary habits suck.
o Be proactive in a non-confrontational way! Find sneaky ways to fit good food and light activity into your lives. Hell, surprise her with a meal you know she’ll enjoy, but make sure it is all healthy. Alternately, instead of you exercising and her sitting on the couch, why don’t both of you go for a walk and do some window shopping?
I know, I know, the window shopping sucks ass. However, she’ll probably really enjoy boring you to tears while she ogles countless varieties of shoes and dresses.
The point is, stop making it a confrontation and sort of ease into it without it being anything in particular. You can start doing the cooking two or three times a week and just be pitching in, especially if it doesn’t come with a lecture.
The two of you can do things together that involve light duty exercise just don’t get too anal if she decides to opt for a frozen yogurt or something while to the of you are doing it.
Also, the women here have a good point, introduce her to a fit women. Maybe PM one or two here who haven’t turned into the hulk overnight and see if they would be willing to discuss diet and nutrition with your wife. People often get the idea that only people like them can have useful knowledge for their own situation – and no matter how much you read here, you won’t get credit for it in this lifetime, at least from her.
P.S. Don’t feed the troll’s trying to hijack the thread…