Filmmaker Shankar says he was swept away by Vikram's dedication for I but at the same time he was worried about his health.
He described Vikram's dedication for upcoming Tamil magnum opus I as "crazy and mad" but added that it had worked in favour of the film.
"For the role of the bodybuilder, I requested Vikram to put on weight. He worked extremely hard for it and we were happy with the output. For the other role of a disfigured man, I never asked Vikram to lose weight but he felt it would suit the role," said Shankar.
"I said it was not required but he was hell bent on achieving it as he found it to be exciting. He was madly dedicated for the role. Going by whatever he's gone through for the film, I sometimes felt he was crazy. But all that worked in favour of the film," he said.
Shankar said he was extremely concerned about Vikram's health.
"It's not easy to gain and lose weight for the same film. He didn't just lose a few kilos, but he lost so much weight that I was worried about his health. I even told his wife that I had never asked him to lose weight," he added.
Also starring Amy Jackson, Upen Patel and Suresh Gopi, I is slated for a early January 2015 release.