I understand the need for the airlines to get as many passengers on board as possible, but honestly ... the seats are small. I’m 6’ and 165lbs and I find the seats to be narrow and legroom to be minimal at best. I can’t imagine being even slightly overweight and trying to sit comfortably on a plane.
Have you ever had the misfortune of sitting next to a tubber? You have to stick your arms straight down at your sides because they need both arm rests. The seats are small to begin with for anyone except kids and midgets.