For his turn as the mysterious villain John Harrison in the upcoming sequel "Star Trek: Into Darkness," Benedict Cumberbatch decided that a physical transformation was in order — starting with his hair. 

"Which way to do my hair was the hardest thing really — straight or curly, or long with bangs (fringe), or a sort of ponytail, or maybe no hair," he told The Independent. After settling on a simple slicked back look, Cumberbatch, 36, then addressed his physical frame. 

"Beyond the bangs, and how I was going to wear my hair, preparing for the role was the hardest thing in all honesty because it meant an awful lot of eating and a lot of working out in a very short space of time," says the actor known for his roles in "Sherlock" and "Atonement." His diet consisted primarily of chicken, potatoes and broccoli to fuel, at times, a necessary 4,000 calories a day for workouts. 

"You turn into an absolute creature from hell because all the fuel you’re relying on to get you through the workout disappears … it’s just horrible," he says. 

He added: "Now I know how girls feel. Diets are s***e."

Despite all off the hard work, Cumberbatch admits that he enjoyed the challenge of bulking up. 

"I’ve never been asked to before," he said. "It’s very integral to the character to have a strong physical shape and presence and be able to move at the same time so he couldn’t be a stiff lump of muscle."

"Star Trek: Into Darkness" arrives in theaters on May 16. Check out a trailer below. 

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