I don't really want to make a huge argument over it, but I see this as a moral grey area. If you have a partner who passes away at an age much younger than normal, and the cause is exacerbated by being some level of obese. It's normal to start pondering, "what if?"The idea that just by being with them you're somehow complicit in their fatness is bunk.
You can argue that person would have been fat anyways, and that's probably true.
My point of view being, I am a weightlifter whose body looks the way it does due to my workouts and what I eat. My tag line, We are what we repeatedly do. Excellence is therefore not an act, but a habit. Aristotle
If you see a potential problem but do nothing to change it or prevent it, you are being complicit. My point still being it's a moral grey area.