Does your wife work in a stressful environment or an environment that is not conducive to healthy eating? Do you guys have children together? I wonder if some of it doesn't have to do with the environment and stress as well.
I work in an environment where you can go all day without being able to sit down and have lunch, and we receive a lot of baked goods and unhealthy food as gifts. That coupled with the stress of the job means that a lot of people grab the unhealthy choice as their sustenance and so have gained weight.
I didn't gain that weight because my partner helps me by making healthy lunches as snacks as their work schedule can be more flexible. I wonder if you'd be able to decrease some stressors in her life and assist with taking over food and snack prep?