Joe Jonas strips down in Guess underwear ads

LOS ANGELES, Jan. 11 (UPI) -- Joe Jonas strips down in his first-ever underwear ads.

The 27-year-old DNCE singer and model Charlotte McKinney star in a steamy new campaign for Guess that debuted online Wednesday.

"?@guess?" Jonas captioned one photo for his 5.3 million Instagram followers.

The former Jonas Brothers singer told E! News he dieted and did "a lot" of boxing and cardio to prepare for the photoshoot. He described the gig as a "fun," "exciting" and "life-changing" experience.

"[It was] my first time doing [an ad] in underwear, so it's pretty exciting," the star said.

"It can be a weird thing to be sitting there in your underwear being photographed, but overall I had a blast," he added. "Everybody on set was great. You feel comfortable."

Guess chief creative officer Paul Marciano praised Jonas in a statement as "a cool and charismatic young man" who embodies sexiness, youth and adventure, according to Hollywood Life. The singer himself said he was honored for the opportunity.

"It feels great to be chosen by Paul Marciano as the male global ambassador for the new Guess underwear campaign," he said. "I am excited to be part of this amazing experience and to be able to represent the brand's image."

Jonas and his siblings Kevin and Nick Jonas came to fame as the boy band the Jonas Brothers. He has since formed the group DNCE and released a first, self-titled album with the band in November.