Justin Bieber says he works out five days a week in order to get the ripped abs seen in his recent shoot for Calvin Klein underwear.

"I work out with my trainer, Patrick Nilsson, five days a week for about 45 minutes each," Bieber said about his fitness routine according to Us Weekly reported. "We do three days splits: back and triceps one day, chest and biceps on day two, shoulder and legs on day three, and abs every other day."

Bieber said he also watched what he ate.

"I'm not a special diet, but I do try to watch what I eat," he said. "I do eat unhealthy sometimes -- I am a 20-year-old guy!"

The pop star's abs were all over the internet Tuesday as news got out that he is the new underwear model for the brand's #MyCalvins campaign.

For months, the 20-year-old entertainer did not speak of his shoot with Dutch model Lara Stone.

"I've wanted to be involved with Calvin Klein for a while now," Bieber said. "Earlier this year, I put up a picture on Instagram of me in their boxer briefs with the #mycalvins tag, and people went crazy for it and it got their attention."

Bieber said the two-day shoot dragged a little bit because he got sick.

"Behind the scenes, everything ran like clockwork -- we'd come in, do glam, and get right to shooting," he said.

When it came to keeping the shoot a secret, Bieber admitted it "was hard to keep things under wraps,"

"The Fashion Rocks presentation was definitely a clue, and I wasn't worried about the negative reaction from the crowd when it happened," Bieber said of the 2014 strip down that got boos from the audience.

Entertainment Tonight Online reported that critics say Bieber stuffed his crotch for the Calvin Klein strip down.

The Calvin Klein shoot is seen as an opportunity to redeem the pop singer from his bad reputation.

Related