David Prowse built him up from 180 to about 200. It was in a lot of muscle mags back in the day.
Here's part of an interview with Prowse discussing his role in 'A Clockwork Orange'. A classic answer.
Q: Did you and Kubrick have any disagreements ?
David Prowse: In my major scene in the movie I had to carry Patrick McGee in his wheelchair down three flights of stairs and then do a dialogue scene as if nothing had happened. I couldn't believe it. The combined weight must have been over 200lbs. Kubrick said "Come on, you can do it, you're a strongman". I said "Yes, but your name's not exactly 'One-Take Kubrick' is it?".