I think it would be a terrifying prospect to be so fat that you could not move at all and were confined to bed and could not even move to go to the bathroom. But, I have thought that there may be a time that I would need a power wheelchair to get around easily. As it is there are limits to how far I can walk and how many stairs I can climb. So if that counts as immobility, I may well be immobile.
I would really love being dominated with no control over with immobility. I'd love to be inflated with Icecream & Heavy Cream til I can barely get out of bed on my own & then some more. AS much as whoever was inflating me wanted to go, I'd let them fatten me & abuse me with their fetishes as much as they'd like.Tbh.