Should fat people have separate seating on Aeroplanes?

I had to fly on a short journey and two fat gentlemen sat on the aisle seat and in the middle. The one next to me hat his fat going over the chair on onto my section, his fat was actually pressing my leg making it numb. I also needed to go to the toilet midway through and it took a very long time for them to get up and I could not go around them, I thought i was going to piss myself. Should flight companies have special seating for fat people?