You catch more bees with honey. My meaning is that you need to give her a reward system. Something that she wants. Maybe affection, kisses for each time she loses weight or even tries. Get her thinking about other things than food. Schedule time to do thing near diner time. Do the thing and come back to food later. Have sex instead of diner. Have her be the more active partner.

If you choose to punish her by living separate lives then she will have no incentive to loose weight. You have to be the positive one. The leader, the man of the house. Exercise at this moment may be difficult for her. So go for walks. Make it romantic. Give flowers not chocolates. Reward her for making the effort. A kiss, holding hands, a nice word something to make her feel good about her efforts.

I have said this many times. Make the change and the marriage will change. It starts with you. Look at the man in the mirror.