Extreme obesity

Has anyone experienced hurdles when traveling by air, especially with cheap and crowded airliners?

What were they?

- for those with big bellies, requiring seatbelt extender?
- for those with wide hips, having to book two seats, or having to squeeze through the door or having your hips brushing against the seats while going down the aisle?

Which were the most limiting and/or embarrassing?

Last time I flew, I was wedged quite snugly into my seat, to the point where I was bulging over the arm rests. Didn't even bother with the toilet, because I would definitely have had issues there.