> 3) the existence of exceptional willpower is a mark of exceptional self-discipline, a level not practical to achieve for most; and that
I don't agree that this is what's going on.
People don't avoid obesity by exceptional willpower. They just have healthy eating habits, usually ones formed during childhood.
Likewise, overcoming obesity and returning oneself to a healthier weight that one can maintain requires changing habits and one's relationship with food.
Habit formation and modification can be difficult, but it's sufficiently well understood that it can be implemented.
The difficulty is getting information into people's hands about how to modify habits successfully (I like the book The Power of Habit), cutting through the misinformation surrounding what constitutes healthy eating habits and how to lose weight, and often just education about how to cook food cheaply and in a way that doesn't seem intimidating to people who are pressed for time and resort to fast food out of convenience.
When people know the concrete steps one must take to achieve something, they become that much more willing to believe they can do it.