Asking for advice for a friend here.
He has medical problems with his leg joints -- I'm not sure what they are specifically, but the upshot is that he can't run or bike at all. He can walk but it becomes problematic if the distances are very long. And according to doctors it's supposed to get worse -- he'll need a cane in a few years and then a wheelchair.
So he's gained a bunch of (bad) weight since his legs got messed up, because he can't run, and he's told me he doesn't like it much but doesn't see what he can do. He's swam sometimes ( but it's "inconvenient") and sometimes lifts weights (though I'm not sure if he just means the ankle/wrist weights in his room). Diet is about as bad as humanly possible, because recently he just let it slide (earlier he had lost a bunch of weight by eating nearly nothing, which is obviously not fun to continue for the rest of your life.)
He's brought it up to me so I don't think it would be totally out of line to offer him advice, but I'm still cautious about wanting to be too much of a busybody. It's not that he is or needs to be a super fitness buff -- but long term, everybody needs some form of exercise. And even he -- not a particularly vain person -- will complain and get discouraged if he gets fat.
So, I'd guess that someone on this site has had a leg injury or disability and found some solutions. What did you do for exercise? Any advice or personal experience?