When the Jonas Brothers first burst onto the scene, they were just your average, janky. Not so much anymore. For his role as mixed-martial-arts fighter Nate Kulina in Kingdom, Nick Jonas, the youngest of the group, put in some serious work in the gym and ultimately gained 15lbs of muscle. But how?

Before the role, Nick weighed in at just shade under 150lbs, barely scratching the surface of a believable weight for a seasoned MMA fighter. Jonas worked with Hollywood trainer Gregg Miele to help reach his goals doing a multitude of exercises that brought him to the level he's at today. Using a mix of pull-ups, overhead presses, push-ups and and dumbbell exercises, Nick Jonas has quickly transformed himself into one of the most ripped guys in Hollywood (don't worry Idris, your title is safe for now).

Image via Racked
Image via Racked

The 22-year old Jonas bro is now looking at a different target audience, and is leaving his pop-singing, middle school themed lifestyle behind. Jonas recently sat down with Men's Fitness to discuss his workout habits further and shed a little more light into his routine.

"I worked with a trainer who showed me some things that I can take with me on the road." Jonas said."Basically, it’s circuit training, so about six exercises, all targeting different parts of the body and then following it up with a two-minute cardio burnout. It's been a really effective workout routine for me, and it keeps it interesting."

As for his diet, Nick cut out most of the carbs and focused primarily on a protein based diet to help shed fat, and build lean muscle. The most impressive part about Nick's transformation is he's been diagnosed with diabetes which makes it that much harder to rebuild muscle and keep blood sugar levels regulated.

"It’s really about just staying on top of it and managing every detail. I had to work with my doctor, making sure all my numbers were good and that I wasn't putting too much stress on my body working out as much as I was. When I work out, my blood sugar goes up. But then about an hour and a half later it drops down low. So, post-workout I would have to not only have protein to rebuild muscle but also carbs to sustain my blood sugar. So when I cut a lot of carbs out of my diet, I had to be conscious of that."

Check out Nick in his role on Kingdom on the Audience Network, and check out his full workout breakdown here.

Image via Racked
Image via Racked

[MensFitness]

RELATED: Is Idris Elba Secretly the Most Ripped Guy in Hollywood?
RELATED: The Most Famous Gym Selfies of All Time