Rebourne: when Jack Osbourne finally awoke from his years as an unmotivated teen drunk, he had one hell of a hangover. The cure: a year's worth of sweat and training, plus a six-day food- and sleep-deprived climb to the top of El Capitan

Jack? As in Jack Osbourne? That chubby, spoiled little demon spawn of Ozzy? Well, yeah, technically. He was the juvenile pothead flailing through MTV's reality show The Osbournes. The kid who seized every chance to party all night, tormented his family nanny and neighbors, and walked out on his dad during a lecture on marijuana use. Isn't he a total waste case? He was well on his way. But he's since kicked drugs and alcohol, dropped 50 pounds, and transformed himself. Jack had the same impulses any teenager does. But because he was raised in the glow of reality-show cameras by the Prince of Darkness himself, he tended to take a few too many rides on the proverbial Crazy Train. He was slamming shots and partying when most boys his age were building forts and playing sports. He's still going to extremes for thrills. But now he's finding them in boxing rings, on top of mountains, or two feet in front of raging bulls in Pamplona, Spain. Once again, he's doing it all for the cameras--on a U.K. reality show called Adrenaline Junkie. But this time, he's also doing it for himself. What about the people who will call this all a publicity stunt? They don't know Jack.

MF: So, you've recently moved out of your parents' house?

JO: I've been sober for two and a half years now. So moving out--I needed it. We get on so much better now. We don't argue as much. At my house up in the Hollywood Hills, it's just me and my housemate and a couple of dogs.

Do Ozzy and Sharon get empty-nest syndrome?

They definitely have that going. Kelly's never home. The house is quiet. No one's around. Mom calls me, like, three or four times a day now to talk.

Tell us about Adrenaline Junkie.

It's kind of a sports show, but kind of an alternative one. Everybody always thinks extreme sports and they think, Oh, snowboarding, skateboarding, surfing. But we took more of a bohemian approach.

In what way?

Well, for example, I trained in Thailand for boxing. I had a fight out there with a local Thai guy. I knocked him out in the second round. It was a full-on KO.

Was he just the local whipping boy or a real fighter?

No, he was in my weight class, and he was going for it. I was 200 pounds then and had only been training for three weeks. I said, "What's the worst that can happen?" Turns out, the worst that can happen is getting knocked out. It just didn't happen to me.

What was your greatest challenge during the taping of Adrenaline Junkie?

It's weird, because every episode is a pretty monumental challenge. The first episode is in Thailand. The second episode, I'm in France, then Spain. I'm doing a lot of rock climbing and mountaineering. I went running with the bulls. That was pretty scary. It's mass hysteria. It's like being in a riot. The ground is wet and slippery and disgusting, covered with beer and piss and vomit, and when I was running, this girl in front of me fell over. That's the most dangerous part about it. 'Cause if someone falls, it's this pileup, and the bull will plow between you and fuck you up. When I bent down to pick up the girl, someone smashed into the back of me. I fell, and the bull went by two feet away from me.

Slim getaway. Speaking of which, what are you weighing in at these days?

From the height of the show, I was 210 pounds. Now, I'm 160. But we didn't want to make it a diet show. It's about a full transformation. I look back and I think, I can't believe that was me, and that was only six months ago.

Do you feel like that gives you an advantage now?

With the ladies? Funny enough, I never had that much trouble last time around. I was pretty confident about shit, and I'm still going about things the same way. But it definitely helps to be in better shape.

You've been romantically linked to Kimberly Stewart, Rod's daughter--any truth to that?

Kim's a friend of mine--just a friend.

But she did give you her, uh, boobs, didn't she?

Yeah. She had her implants removed, and jokingly, I was like, "Can I have them?" She was like, "Fuck off, I'm having surgery tomorrow, and it's no joke." Lo and behold, a week later come flowers and Kim's boobs in a case. Now they're hanging in my bathroom.

What do you give a girl who gives you a gift like that?

A high five.

Has the show had a lasting impact on you?

Having done this show and the rock climbing, I got inspired, and that was something I had been lacking. I had nothing to wake up to and make me realize that everything's OK because I have this thing in my life. You know, kids today, they watch MTV. They play video games, and they go to the mall--they lack that inspiration.

Are you coming out against MTV?

Yes, I am. 'Cause they didn't pick up my show--they said I couldn't do it.

You've spent a good chunk of your life on TV, but you keep coming back for more. You're not sick of it?

With The Osbournes, it was like I woke up one day and there were cameras in my house.

The next day they were still there ... and still there ... and still there. But this show was probably the best thing I've ever done. I wanted to do it, and I've never worked so hard in my life. I was committed to this thing to the core. If I failed, I failed at the challenge I'd set for myself.