You're ignoring the fact that poor people are MORE LIKELY to be overweight than wealthier people. I will grant you it isn't all to do with fast food, a lot of it is to do with plain old unhealthy food and I will grant you that very poor people can't really afford fast food. But when you're making minimum wage and you have the choice of a $3 burger meal and a $5 salad, you're going to pick the burger meal.

I'm not saying it isn't a choice, I'm just saying there is a lot more to it than that.