Almost any actor, even some of Hollywood’s most scrawny, can be physically transformed for the part if he’s willing to put in the hard work. The studios know this, which is why any inexpensive unknown can be chosen. ...
For last summer’s megahit “Man of Steel,” Snyder sent Cavill to work out with Twight. “I wanted Henry to be the personification of physicality,” Snyder told me. Cavill and Twight worked together for five months before production started and continued training during the six months of filming. Twight packed the pounds onto Cavill’s 6-foot-1 frame by putting him on a 5,000-calorie-a-day diet. Leading up to Cavill’s two shirtless sequences — a few days at the beginning of October 2011 and about six days at the end of that month — Twight scaled Cavill’s caloric intake back to about 2,800 calories. According to Twight, the pressure on Cavill was intense: “Henry was not a well-known guy, and he had chosen to be one of greatest comic-book icons ever. You’re not going to give that guy an inch.”
The whole physical transformation process is also part of the promotional campaign for the movies. That was part of Sylvester Stallone's brilliance in the 1970s-1980s to tap into this previously inchoate longing on the part of the audience that that the early 20th Century German poet Rilke (who has become a posthumous self-help guru) summarized as: "You must change your life."
A number of trainers and actors told me that steroids were out there and that everybody had a good idea of who was on them — though nobody is willing to name names. But as trainers like Twight make obvious, the Hollywood fitness mechanism is brutal and advanced enough to make any performance-enhancing drug seem primitive by comparison. “Post-‘300,’ there is a machine in place — it doesn’t work for everyone, though,” Twight said. “Not everybody can handle the training.”