My theory is that military men tend to have a relatively conservative or conventional view of society, so their wives tend to be of the stay-at-home variety. With the way life's conveniences have gotten and how apeshit most people's diets are now, staying at home without an intentional focus on taking care of yourself is a recipe for fatness. And that's for the middle-of-the-road ones, who were respectable before they got fat. A full-on dependa is a different breed entirely, i.e. a parasite. Of course a parasite without any drive or general redeeming qualities is going to get fat.