It depends how tall and how overweight you're talking. I suspect most places cater for one standard deviation of height and weight. Two, maybe? Three probably

It depends how tall and how overweight you're talking. I suspect most places cater for one standard deviation of height and weight. Two, maybe? Three probably not. There's no single threshold to say you're fat and you're thin. I'm sure cinemas could put big seats in for the overweight but at some point that 99.99% person is going to visit and be too big even for that.