Shit I was locked up for a year. Federal. Food was good as hell. Got as much as I wanted cause I worked in the Kitchen, and I used to be cool with everyone. Shit you can't ask for anything more. I think I ate better in jail than I did in the real world. Plus you have to think. Sleep is huge when it comes to gains. Shit I slept about 12 hours a day. So basically, you wake up and eat breakfast, then you come back to you Unit and Chill ( I always slept some more ), then you go to lunch, come back read a book or watch tv, go to dinner, get back, relax and then wait for Free Weights to be called. Go work out at around 6:00 PM. Come back at 7:00 go to sleep or watch TV. I new about 20 dudes in there that gained about 50 pounds in less then a year. I know one guy who did it in 4 months. Straight muscle. Next to no fat on him...
I gained about 35 lbs. But I used to go to Gym call ( basketball ), which kept me from getting to big. Cardio will definitely hamper your gains....