EXCLUSIVE: Why Jonathan Tucker Lost 20 Pounds to Embody a MMA Fighter on 'Kingdom'

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"It was a 24-hour process," Jonathan Tucker tells ET about preparing for the role of Jay Kulina, an abrasive MMA fighter following his father's footsteps in the sport, on the Audience Network series, Kingdom.

The series, now airing the latter half of its second season, tells the story of a family that literally puts all their blood, sweat and tears into the MMA fighting world. The intensity of the show and its characters is not lost on Tucker, who puts in the same amount of effort into accurately creating this world onscreen. "Kingdom just kind of heightens all of these relationships and dynamics and characters and allows you to go further or higher or lower than you would on other shows," the actor, who was previously known for his recurring roles on Parenthood and Justified, says. "It's certainly the case with the physicality, in terms of putting the character into your body. How do I make an audience believe I'm as capable and talented as a fighter as Jay is?"

For Tucker, it's a full commitment to a role that he pursued after first being asked to audition for the part of Ryan Wheeler, an ex-con turned fighter, who is now played by Matt Lauria (a fellow Parenthood guest star). "I just felt very attached to Jay," Tucker says of the role, which he says has all "that range you want as an actor."

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To embody Jay's physical presence, that means an extreme diet and training regimen that sees Tucker dragging himself to the gym after a 16-hour day of shooting. At the end of the first half of season two (2A), he lost 30 pounds.

"Then, I lost another 20 at the end of 2B," he says, explaining the critical need to go to such extremes. "The thing is, we're trying to honor this subculture. You have people who are really living these lives. We're trying to really represent them in a just and honest way. So, audiences know when you've lost weight or not. You can't really hide that. Cutting weight is one of the biggest parts of fighting. Once you make weight, the fight is really just a reward."

If the diet and gym weren’t enough, then a stray elbow to the eye or ripped cartilage on the ribs would be for most actors. "That was the most painful," Tucker says of the injury that made it painful to even pick up a toothbrush. But he says it all parallels life in the MMA cage. "No fighter fights at 100 percent. You keep pushing through. Ultimately, we have to do the very best with the circumstances we’re given."

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As Jay, Tucker makes the most of it, especially in the scenes that go beyond the fighting, such as when he witnesses his mother (Joanna Going) overdose on heroin. "It's the scene you're eyeing for as an actor on paper and then on the day, you open your door and it's really happening," Tucker says of the challenging film experience. "It'll be really happening from zero to 100 miles per hour for the next six hours. Seeing people, that I deeply care about as Jay, lose their footing is -- it crosses over between the character and my personal life."

The bonds formed on-set are just part of the intensity shared between the cast and crew to meet the very high bar that creator Byron Balasco has set for them. "We need to do right by that," Tucker says.

"When you're an actor, you end up opening yourself up very quickly and very frankly with people who you are in a relationship on screen," Tucker says particularly of Nick Jonas, who plays his bother on the series and with whom the actor co-wrote the song, "Champagne Problems," for Jonas' new album. "We worked together during the course of that. We talked quite a bit about some of those issues that he was wrestling with and some of those issues came into that song."

And while playing Jay is a professional high for Tucker, the songwriting credit is one of those unexpected perks of the job. "It's one of the great highlights of my life as a completely non-musical person to be involved in a small way on his new album."

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