Fashion & Beauty

Nick Jonas: ‘Sex is a healthy part of life’

As a jacked-up, buzz-cut cage fighter with sex scenes galore, you’d never recognize Nick Jonas from his celibate, scrawny boy-band days.

Truth is, Nick, the star of DirecTV’s brutal drama “Kingdom,” is still trying to grasp the potency of his new ripped bod himself.

“I have been trained very well by some excellent fighters, so if anything ever went down I’d be worried that I would use the training and then get in trouble,” admits a baby-faced Nick, who says he’s never been in a real-life fight before.

Lucky for the 22-year-old, his bodyguard is just outside.

We’re sitting at Nick’s “favorite spot in the whole world,” Ovest Pizzoteca in Chelsea. (He’s eating his go-to order, the Martha, a pizza made with mozzarella, prosciutto, truffle pâté and basil.)

The singer, sporting a leather and shearling AllSaints jacket, just finished lunching with his brother Joe and a friend, fashion designer Richard Chai.

“Oh yeah, this is a treat day and an indulgence for sure,” says a scruffy Nick, who put on 15 pounds of muscle for “Kingdom” (he since has shed 10 of them).

The superstar has plenty of reasons to treat himself.

In the last three months, Nick has released his hit self-titled solo album (which sounds as though soulful R&B singer Miguel and pop star Justin Timberlake had a love child), signed a Wilhelmina modeling contract, starred in a television show, and made postmenopausal women — and just about everyone else — sweat with his viral Mark Wahlberg/Calvin Klein-inspired Flaunt magazine spread, where he posed in nothing but a pair of tighty whities and a smirk.

All-American boy Nick Jonas instigated the split of the Jonas Brothers.Randall Slavin

“I was at a basketball game the other day and a few older ladies came up to me and said, ‘I love the new song!’ ” recalls the surprisingly soft-spoken celebrity.

“And then they go, ‘And we love the shoot, as well!’ That was an added compliment,” he says with a laugh.

Like many brave Disney-branded cohorts before him, including Miley Cyrus and Zac Efron, Nick has finally broken free of his PG image, seemingly reinventing himself overnight from cutie-pie crooner to sultry sex-symbol badass.

In case you had any doubt, the purity-ring, Jonas Brothers days of yore are over (even if Nick still requests a box of fruit snacks in his rider).

“I think I’ve come out of my shell quite a bit,” says Nick, who’s been dating professional beauty Olivia Culpo, 22, Miss USA and Miss Universe in 2012, for a year and a half.

Jonas says he stopped wearing his purity ring “a few years ago.”Randall Slavin

Culpo even starred in the video for Nick’s single “Jealous,” about a boyfriend who can’t handle other men flirting with his girl. It peaked at No. 8 on the Billboard 100.

“I think earlier on in my relationship, there were times where I would get jealous,” says Nick, who’s dated a bevy of famous women, including Miley Cyrus and Selena Gomez.

He continues, “I think with time and trust built up, a lot of that went away. We have a really strong relationship now. It takes a second until you feel really locked in with someone.”

For many Jonas Brothers fans, it’s difficult to think of Nick as anything other than the eternal virgin. But Nick, who grew up with a pastor father and stopped wearing his purity ring “a few years ago,” says his sexuality “happened for me over time.”

“Sex is part of a healthy life,” explains the singer. “So I have tried to be, in my transition into adulthood, as honest with myself as possible with sex and sexuality and what it means to me, so I can try to be as healthful as I can.”

Jonas says he hopes couples get it on to his songs — but that he wouldn’t make love with his own music playing in the background.Randall Slavin

This is coming from a guy who was once so petrified of his puritanical, good-boy image being shattered that he made his hotel bed each morning. Needless to say, times are a-changin’ for Nick Jonas (though he still makes his hotel beds, but only out of habit and cleanliness, he says).

Last October, the Jonas Brothers, composed of Nick and his older brothers, Kevin and Joe, officially parted ways.

Nick admits he instigated the split.

“There was a bit of shock when I first said it was time for us to close that chapter,” he says. “But after we opened up the conversation, there was a real understanding of all the points I was making, and they agreed that it was no longer right.”

Nick wanted to veer away from the group’s saccharine pop sound and pull in elements of soul and R&B to “make that record I never got to make when I was young.”

Jonas and girlfriend Olivia Culpo in NYCROLO-AKM-GSI

The Jonas Brothers were formed in 2005 out of what was originally a solo project for an 11-year-old Nick, who had been performing on Broadway since the age of 7. Columbia Records’ then-president, Steven Greenberg, liked Nick’s voice, but signed the brothers as a trio instead. The Jonas Brothers were a massive hit with tween girls.

They sold over 20 million records, produced four albums, and were part of the Disney star-making machine. (They had their own series on the network called “Jonas,” and starred in the 2008 Disney movie “Camp Rock” and its sequel.)

In 2010, the brothers took a break to pursue solo projects. In October 2013, to the shock of fans, they canceled their much-anticipated comeback tour days before its start date, citing — in an unusually candid official statement — “a deep rift within the band.”

Nick says the Jonas clan remains a happy family and that his brothers have been nothing but supportive.

“We genuinely like to see each other succeed,” he says. “If the individual pieces of what was a group situation win, then we all win. It shows that we’re hard workers and cut from the same cloth. People recognize that. I’m excited to see what happens with them.”

I have tried to be as honest with myself as possible with sex and sexuality and what it means to me, so I can try to be as healthful as I can.

 - Nick Jonas

Currently, 25-year-old Joe is working the DJ circuit, and 27-year-old Kevin has settled down in New Jersey, where he is a contractor and lives with his wife, Danielle, and 10-month-old daughter.

Kevin had a hard-hat cameo on “The Real Housewives of New Jersey,” where he was on air building one of the matriarch’s new McMansion.

“It was hilarious,” says Nick. “He did a great job. It was a good plug for his business. I don’t think people knew he was doing that, so it was a surprise to see him in that light.”

Meanwhile, the baby Jonas Brother is relishing the success of his album and learning to enjoy the perks of solo fame.

“I look back on the craziness with the Brothers and think about the things that I was stressing about,” he says. “Multiple trips to the White House performing for presidents, being nominated for Grammys . . . But this go-round, I told myself to have fun, to enjoy it, and find a way to take a step back and take in each moment.”

The newly open-minded Nick implores fans to make sweet love to his music. But when asked if he and Olivia get it on to the “Nick Jonas” album, he shudders.

“No, absolutely not, you can’t do that!” he responds, and admits a penchant for James Blake and Jessie Ware to set the mood. “That’d be so uncomfortable.”

FROM TOP: Bomber jacket,$2,450 at diorhomme.com; Shirt, $98 at jcrew.com; Frame Denim jeans, $248 at barneys.com; Tie, $15 at topman.com; All other accessories, Jonas’ own; Calvin Klein collection suit, $1,795 at Calvin Klein, 654 Madison Ave.; Helmut Lang shirt, $245 at barneys.com; Bally jacket, $3,995, call 844-44BALLY for availability; V-neck, $24 at americanapparel.net; “Datejust” watch, $9,900 at rolex.com; Jeans, $58 at levis.com