How can i loose weight when i am using cortisone i have gain 20 kg i am really fat any advice?

This is a: challenging problem. First make sure you are taking the cortisone exactly as prescribed and your doctor wants you on the dose you are taking; you want to take the minimum effective dose. Weight gain is almost universal. Really all you can do is really fine tune your diet to a healthy 1200 calories/day and add in 35-45 minutes of daily moderate exercise. It's a battle that you can win! Stay well:)