Mates,
OP is in a unique position, different from all the rest. As such, the advice should be tailored to his unique set of needs.
Of course, diet is important, but his complaint is not able to lose weight. If I’ve heard him correctly, he seems to be gaining weight due to a shifting metabolism. His base metabolic rate is decreasing, and he is finding it difficult to do anything about it. Everything else being the same, he would need to do MORE cardio given the same diet than a normal person, since confined and inactive in a chair most of the time. And People in wheel chairs have a harder time with cardio.
The best thing you can do, since i don’t know much about your condition, is to discuss this issue with youur doctor. He may be able to work up complete blood panels, including thyroid. If your thyroid is low, some T3 could reboot your metabolism. Additionally, you may have low testosterone . If so, replacement therapy may be of help. It’s really hard to tell what is goiing on without the blood panels though, so highly suggest getting them.
Get the blood panels, and then come back and let us know what is going on.
Good luck!
—Roman