The real problem is that most airplane seats are inappropriately sized and uncomfortable for adults of average size. I'm not particularly tall, less than 6ft.,

The real problem is that most airplane seats are inappropriately sized and uncomfortable for adults of average size. I'm not particularly tall, less than 6ft., and I can't recall ever having adequate leg room on any flight except when I happen to be seated in an exit row where there is no seat in front of me. If the seats were appropriately sized for average adults, a large person (whether fat, tall, or both) would be no more uncomfortable than what an average size person is now and would not require any special accommodation from anyone in an adjacent seat.