How Can Excessive Weight Gain And Water Retention In The Body Be Reduced?

I am a survivor of two double lung transplants. I am immune suppressed on low dosage of prednisone, tacrolimus, acyclovir, mycophenolate, metoprolol, and Bactrim. I am 62 years old and 6.5 years post transplant on my 2nd surgery with no complications or events since my surgery., not even a common cold. However my prolonged use of prednisone has resulted in weight gain and bloating around my waistline. However my overall weight is 166 and my height is 67 in. I can do sit-ups everyday for a year with no impact on my waistline. Is there anything that I can take for bloating and water retention besides prescription diuretics that won t have an adverse effect on my anti rejection meds? My transplant team would rather I not look at any possible solutions herbal or medical. So I m simply seeking info and another opinion. I would never take any medication or supplement without first getting the ok from my transplant team but always looking for new ideas