I totally get what you're saying but I know a LOT of fat people (some of whom are wheelchair-bound) and can honestly say that not a single one got fat from being chronically ill and not able to exercise... they got to that point because they ate too much, moved too little, or had serious mental issues that triggered emotional responses that drove them to eat small armies with alarming regularity.

Your case is definitely an exception. I've yet to meet a fat person stuck in a chair that didn't get their because of their gluttony and sloth. Sad to say from my own observations... because the people who didn't want to get fat and did end up being stuck in wheelchairs found alternate means to exercise or upped their calorie management game to compensate for a lack of consistent walking.

There is is never an inability to exercise unless all your limbs have been blown off. I've seen guys weightlift with a single arm and a classmate years ago would ask to be strapped into a machine so he could use it (since he was missing a leg). Where there's a will there is always a will... and people who got fat on their own accord simply lack the will. No contest.