No one's going to do a study on drug users because of the side effects and increased cancer risks associated with gh use/abuse.
Lower doses don't seem to increase weight but definitely make people leaner. Short term gh seems to directly decrease insulin sensitivity but indirectly increase it through liver production of IGF1. Long term use increases insulin sensitivity directly and indirectly. That's why Van_Pilsnerass
is sort of right too. It's just doubtful that the typical user is only doing the drugs short term and with any moderation. Either steroids or their effects are addictive to some and we also know there are a lot of people who are never 'off'.
I doubt anyone will ever do a great study double blind study on bodybuilders with follow-up evaluations of the same people at specific intervals. It would be pretty expensive, take a long time, be dangerous and have no medical benefit because the results wouldn't have any effect on the culture. By "effect" I mean specifically mean decrease use.
I personally feel it would be great if someone studied and came up with definitive, safe, peer reviewed guidelines for off-label and/or recreational/professional drug use. It'll probably never happen but I still feel it would create a bigger safety margin for people who are going to use anyways.