I never thought that Reeve bulked up for Superman. He looks just like a man in tights.He's too skinny.
So was Christopher Reeve when he was first cast as Superman. Actors bulk up for roles all the time.
Not that I can really see Bloom as Batman . . ..
No he bulked up, David Prowse (Darth Vader) trained him and put him on a four meal a day high protein diet - when they originally cast him there was a worry that he was too thin to be a convincing superman and there were plans to put pads in the costume:
Christopher got so caught up in the property that he rejected the option to have costume men build his physique with Styrofoam falsies. When signed, Reeve was 6'4", 188 pounds and looked, he admits, "like Jimmy Stewart standing sideways. I had to get to a state where I could believe I was Superman."
To that end, the producer hired body builder David Prowse (who played Darth Vader in Star Wars). After the first workout, Reeve confesses, "I went into the locker room and heaved." But in 10 weeks of weight lifting and a four-meal-a-day high-protein diet, he gained 33 pounds and added two inches to his chest.
As for strength, he raised his initial bench-pressing record of a pathetic 40 pounds to 320.
http://www.people.com/people/archive/article/0,,20072681,00.html