Don't know about that disease. Are you allowed to do weight lifting? That is the number one way to lose weight. Muscle burns fat, muscle burns fat, muscle burns fat. Lifting weights builds muscle.
Seek the opinion of your doctors and if allowed to do this start slow, under the guidance of a professional trainer.
Some hospitals have expanded their physical therapy area to include a gym for outpatient use. If you have that available you can get some good guidance there.

Vegetarian Diet