There are plenty of physical challenges that go along with being fat, especially very very fat, in public.
By the time I hit 400, I had to be mindful of spaces and plan carefully. Does a restaurant only have booths? Is the seating arrangement spaced out enough I can get around without knocking into other diners? Is the Uber that's on the way easy enough to get in and out of?
After 500 lb, there were even more considerations. When my husband and I got married, I was right at 585. We had to plan out every aspect of our honeymoon, including bringing my own bariatric wheelchair to the airport because we knew even their largest chair wouldn't work for me. We bought additional plane seats for me, and I sat in the front row because of how much my stomach bulges out in front. I had my own seat belt extenders, because even the airlines extenders, available upon request, are not big enough to go around me. We ensured I would have a walk-in shower and requested bed reinforcement, which they were able to accommodate. I shipped my own bariatric shower chair ahead, so it would be waiting when we arrived.
Now, at 800 lb, travel would be impossible. I haven't left the house since the last 70 lb or so, because a) I have no clothing that covers me at the moment, and

getting out of my front door is very painful. It's not impossible, but we have to manipulate my body and my fat in such a way I don't get injured. I also have to be mindful, if I were to go to a business like a restaurant, that I'd need to remain on my scooter. I don't trust other chairs, even two of them, to hold my weight. Moreover, I don't want to be injured in a fall. I have fallen in my home before (I was about 660), and firefighters had to help my husband get me up.
As far as the social aspect of being fat in public, I've always enjoyed the stares, particularly if I'm eating a big meal while fat. I wore bikinis on my honeymoon, and being gawked at was a turn-on for both my athletic, fit husband and me.
As I've gotten even bigger, people tend to look much less than they did 200 or 300 lb ago. It's almost like my size is so extreme, people avert their eyes, as though extreme obesity is contagious. I do catch children staring though, and I always make eye contact with them and give them a reassuring smile. Usually, they smile back. I think there's a lesson there that even people who look very different are people too.
One last observation... People tend to overestimate my age, particularly if my hair is pulled back. I have a youthful face, but it's very uncommon for a 31-year-old to have gotten this big and to need a mobility scooter. Unless I have my long hair down, fully styled, people often think I'm an older relative of my husband's.