AceShowbiz - "Twilight" hunk Kellan Lutz hired a personal trainer and sacrificed his love of sweet treats before shedding his clothes for a sizzling photoshoot for Calvin Klein Underwear. Lutz, who started out as a model for American clothing brand Abercrombie & Fitch before pursuing a career in acting, was unveiled as the face and body of Calvin Klein Underwear last year.

He admits he had to work hard to tone up his stomach and leg muscles so he could look his best in the revealing adverts, telling the New York Times, "You have to look like you enjoy what you're selling. It doesn't look that hard, but a lot of people don't think about what goes into it."

But the movie vampire's hard work has paid off - and he's happy to receive compliments for the sexy billboards, which have been erected in and around Los Angeles and New York. He says, "I won't lie about it. I started getting text messages and calls from producers, and when I went into meetings for scripts, people were always commenting on the billboard and asking for pictures for their daughters."

Lutz's Calvin Klein adverts come almost 20 years after Mark Wahlberg stripped off for a similar campaign as the brand's spokesmodel.