Besides enhancing performance, PEDs are taken by athletes and fighters because they help maintain and build lean muscle mass better than exercising naturally. Here is a research published in The New England Journal of Medicine: (http://www.nejm.org/doi/full/10.1056/NEJM199607043350101) They found that men who took Testosterone and DID NOT exercise (second column from left) gained MORE MUSCLE MASS than those who exercised naturally (third column from left) ..........................(1st)........ (2nd)......... (3rd).... (4th) What this means is if someone were to take Testosterone and sit on his ass watching TV all day, he would still gain MORE muscle mass than someone who works out regularly but is natural. EDIT: Here is another study done on 18-35 year old males: http://www.ncbi.nlm.nih.gov/pubmed/11701431 Up to 600mg of Testosterone were given for 20 weeks (5 months). The men were NOT on any exercise programs. The lean mass gained was 7.9kg (17 lbs).