There are a couple good alternatives to steroids that are legal and don't cause the health side effects that steroids do. The best alternative is to go to the gym and start working out - especially lifting weights. Weight lifting is a natural way to build muscle mass in your body. However, lifting weights does take time (more time than using steroids), effort, and dedication (to not give up before you reach your muscle-building goals). Another good alternative to steroids is to combine weight lifting with protein supplements. Whey protein is readily available in most stores (and is 100% legal). Also, using protein supplements don't cause the negative health side effects that steroids can cause. In short, the best alternative to steroids is to combine weight lifting with a protein supplement to build increased muscle mass while working out.