The only way to lose the weight is to get off of prednisone. I've had asthma all my life and have had to take prednisone off and on and it always causes the bloated look because it is a steroid. It is not good for your body to be on prednisone long term either. Please talk to your doc and see about getting off of the prednisone and on to something else. If they won't work with you find another doctor! My doctor only uses prednisone in short bursts because it is so bad for your body. Here are some side effects...
(From medicinenet.net) Side effects of prednisone and other corticosteroids range from mild annoyances to serious, irreversible damage, and they occur more frequently with higher doses and more prolonged treatment. Side effects include retention of sodium (salt) and fluid, weight gain, high blood pressure, loss of potassium, headache and muscle weakness. Prednisone also causes puffiness of the face (moon face), growth of facial hair, thinning and easy bruising of the skin, impaired wound healing, glaucoma, cataracts, ulcers in the stomach and duodenum, worsening of diabetes, irregular menses, rounding of the upper back ("buffalo hump"), obesity, retardation of growth in children, convulsions, and psychiatric disturbances. The psychiatric disturbances include depression, euphoria, insomnia, mood swings, personality changes, and even psychotic behavior.
I am not trying to scare you but you need to get this out of your body ASAP!