Thank you for your question. I am Dr Asanghanwa Carlson. Steroids are very power drugs and have many effects on the body and these effects are generally exploited to treat many conditions. These effects are notably antiinflammatory, anti allergic, immunomodulatory just to name a few. however they have many side effects like weight gain, skin lightening, diabetes, gastritis, adrenal insufficiency, muscular diseases etc when used on long term. Using steroids for weight gain means you only want to exploit that aspect of the steroid drug but the other effects will also be felt as well and these are potentially dangerous and life threatening and costly to treat if they arise. I strongly will advise you against the use of steroids for weight gain. I advise you see a dietician so an appropriate diet is prescribed for you. Have a great time and best regards