Glad to see Gracie placing some actual knowledge on the topic here. Everything he said seemed to be on point with a friend of mine who spent two years in state prison. He went in around 240 and came out between 260-270. Said they didn't have much though in terms of equipment, the basics with a little here and there in terms of old school machines and stuff. He also worked on the kitchen staff and would smuggle things like various meats, cheese, etc. out for himself. He said his responsibilities were minimal too, and not much physical activity going on besides actually working out. Said it was the best training of his life, but found out that lifting wasn't everything. Kind of puts things in perspective.
