I have been on and off of prednisone for the last yr with just temp results. I did not experience the weith gain you did. This last time I put myself on a very restricted diet. No sugar(honey included)no white flour, no pop, alcohol, red meat, night shade veggies junk food of any sort, no nuts, popcorn the list can go on and on . This diet first started from a naturalpath and I revised it a bit, if you are able you should seek one out in your area, they know so much more then doctors when it comes to diet and I am living proof that diet really does make a difference. All I eat is veggies, deer,lamb ,fish ,turkey, chicken and spelt bread olive oil balsalmic viniger and I take vit e, selium and vit c. I feel so much better and have actually lost 10+lbs and I was on 30mg of pred a day . I am now down to 10 and will continue down to 1 mg very slowly as I had a very adverse affect as well. I also found that splitting the dose throughout the day helps. I take 10 in the morn, 10 at lunch and 10 at supper.
There are also some very good books on the market to help us,THe Immune System Cure by Lorna R, Vanderhaeghe, as well as Be good to your gut.
Hope this helps