I am fit and lean so I am paying for some of the fuel that your oversized body requires to become airborne. That's not the problem--I am willing to pay a little more-- the problem is when your body crosses over the armrest and invades my space. I'm already paying for part of your flight now you want part of my seat too! Ok so if I slide over a little--I can give your years of surplus calories another few inches but its never enough. Fat seems to take on the shape of its container and it keeps coming over until contact with my body is made. Do you have any idea how gross that feels to a person not accustomed to fat containment? Or is it like the smoker who does not realize that his breath, clothes, car, house, wife, and kids all smell of cigarettes? Please pay for the extra seat or fly first class where you have more room.