Hey, man, cancel everything. We're hanging with Rick Rubin tonight. You know Rick, right? No? Check your iTunes playlist. Kid Rock. LL Cool J. Metallica. Jay-Z. All Rick's audio kids. He once had Tom Petty write songs using refrigerator-magnet words! Dude is Phil Spector minus the fright wig and the .38.

Rubin has won seven Grammys, resuscitated Johnny Cash's career, and has somehow gotten three number one records for a bunch of Armenian-American art metalheads. Man's a genius for that one alone. Tonight, System of a Down – said Armenian metalheads – are headlining at the Forum in Los Angeles. Rubin wants to see his old friends, so we're going. This is a big deal. Rubin, who is 48, doesn't leave his Malibu pleasure dome very often, but he's putting it into gear for SOAD.

Instructions are texted. Be downstairs at 5:30. No, make that 6:30. Check that. 7:15. Still waiting. Out front, a sailboat bobs in the sea as the sun sets over the Pacific. Two minutes away, promise. A white Range Rover finally arrives, and a surfer Santa pops out. His skin is the color of cinnamon, the spice he likes to sprinkle on his organic apples. He speaks in a soft, dreamy indoor voice.

"Hi, I'm Rick. I'm going to ride in the back with you."

The beard doesn't surprise. Rick Rubin's undulating face hair is just as famous as his body of work. In homage to the yogis he read about as a boy on Long Island, Rubin hasn't shaved since he was 23. It's long been his registered trademark.

The rest of his getup does surprise. He's wearing a white T-shirt, Technicolor slip-on sandals, and skimpy black gym shorts. Actually, skimpy isn't the right word. More like genital-hugging. An intriguing choice for a man who moonlights as co-chairman of Columbia Records.

But something is missing. Something big. Something that is as much a part of Rick Rubin as his decadelong partnership with Johnny Cash, his nurturing of the Beastie Boys, his chocolate-in-my-peanut-butter meshing of Aerosmith and Run-DMC.

What's missing is half of Rick Rubin. When he used to listen to music, he would clasp his hands in front of him, his pasty arms barely reaching around his Buddha belly. But now as we talk, the same gesture looks storklike, ­like Gandhi before lunch. He's got too much arm and not enough girth. What happened?

Rick Rubin dropped 130 pounds in 15 months. How it happened will amaze, inspire, and freak you the fuck out.

He swears he didn't lose the best part of him.

It's not like Rick Rubin has been scarfing down White Castles for the past two decades. Okay, he did that as a kid. He also consumed 64 ounces of Pepsi with every meal, but that was a long time ago. Rubin was a vegan from age 23 to 46.

Before that, he says, "I wasn't eating anything except chicken and vegetables." Then a friend gave him the vegan bible Diet for a New America and predicted that he would never eat meat again.

Over the next couple of decades, he didn't eat meat, but Rick Rubin got up to 320 pounds. Some of that was genetics. Some of it was a lack of exercise. (Rubin always took the elevator.) And some of it was a profound misinterpretation of the vegan approach. Dave the Driver steers us onto I-10 while his boss speaks in a soft voice. "I used to eat tons of almond butter. I thought that was good for me. It turns out it's very high in caloric content."

Indeed it is: 190 calories a serving, 150 from fat. I want to ask who told him that eating large amounts of almond butter was good for him, but Rick interrupts.

"Dave, can I have a protein shake?"

We're late, so Dave is passing cars at 75. He flips open a cooler and hands Rick a plastic cup. He gives it a shake.

"Love these. Lots of protein. Egg whites, a little stevia, and Teeccino for taste."

I've heard of one of the ingredients.

Rick takes a sip and lets out a contented sigh. "I drink seven of these a day, so I'm never hungry. Sometimes I'll add some blackberries. That's good fruit. I avoid bananas and pineapples. They're too high in sucrose."

Dave jumps a curb and we're in the parking lot. Rick is so serene he notices no bumps. For years, he also didn't notice his expanding waistline. He produced the last six Red Hot Chili Peppers records, and over time hard-partyers-turned-health-nuts Flea and Anthony Kiedis began suggesting Rick might want to see a doctor and take the occasional walk. But his health kick didn't start until a scared-straight lunch with one of his heroes, legendary record executive Mo Ostin, who told him he was going to die if he didn't change his ways. Rick promised his 84-year-old friend he'd try to treat himself better. Immediately, he started researching diets.

"I just started eating meat again," Rick explains. "And eggs. When you're vegan, you spend your time chasing protein, and you're eating food that's way too high in carbs. I could never catch up on protein."

We're at the wrong entrance. Dave executes a perfect three-point turn, burning rubber and scattering the guys hawking bootleg System of a Down T-shirts on the median. Rick's eyelids don't even flutter.

Rick's meat has to be masked. His cook makes a turkey chili in which you can't even taste the turkey. He talks about eating meat as if he's reintroduced eight balls into his life.

"I'm trying red meat," he confides. "Very traumatic. I've done it four times. Very small amounts. It takes a while before you get over the idea that eating flesh is not okay."

Dave pulls onto the arena's loading ramp. Dudes in yellow windbreakers wave us in. Rick opens the door. Dave pipes up.

"Rick, you want a protein bar?"

"No, maybe later."

We enter the Forum. Rick's few remaining locks are sun-bleached and flow behind him like Misty of Chincoteague's mane. We sprint toward the side of the stage. Rick has also produced the opening band, Gogol Bordello. It's their last song, just enough time for Rick to move to the side of the stage where the guys can see him. Rubin closes his eyes and bobs gently. The Bordellos smile and hug him before the last chord fades.

Then we're in the bowels of the arena. In one dressing room, there are still basketball diagrams on the wall from when the "Showtime" Lakers played. Magic and Kareem stood right here. Now it's the private court of Serj Tankian, System of a Down's lead singer. Rick sees Serj and does a little Buddhist bow.

Serj has a tug of chin hair, but he's lost the Armenia-fro and cape from the band's 2001 heyday, replacing them with a Clooney cut and a crisp white shirt.

"Rick, you look great," he says.

Rick smiles.

"How are things?" Rick asks.

"Good, everyone seems to be getting along."

Rick nods.

"Just enjoy the moment."

Serj also nods, and his eyes light up.

"Hey, I've been doing those morning meditation exercises before I get out of bed."

"Yeah, aren't they great?"

Soon we split for the parking lot. There's a secret knock, and we're admitted on guitarist Daron Malakian's magic bus. The vibe is a little different.

"Smells like skunk in here," Rick jokes.

Daron laughs.

"Yeah, we're getting ready for the show."

A hanger-on chimes in.

"This is the least high I've seen you all week."

Daron rolls his bloodshot eyes.

"Really? I've been getting baked from the moment I woke up."

"Just enjoy the moment," Rick tells him. "I hear everyone is getting along."

Daron shrugs and places a black top hat on his head.

"I guess so. Serj is by himself in his mood room, right?"

Rick smiles but reveals nothing.

Someone shouts."Time to walk!"

So we walk, a haze of weed behind us. We're back in the bowels. There's a Spinal Tap wrong turn and we're in another holding room where roadies roll joints in front of Armenian grandmas. Trailing behind us, a fan says, "That's Rick Rubin!" Someone else shouts, "No fucking way. Rubin is fat."

In five minutes, we're cruising toward Malibu. Rick asks Dave to flip the satellite radio to a Big Band station.

It's getting late. Well, actually it's only 10:40, but in Rick Rubin's brave new world, that means closing time. He used to stay up until 5 am and then sleep until two.

"I hated the sun, and I loved sleeping through the conflict part of the day."

But then a performance coach (yes, he employs such a person) told him that wasn't natural for humans. Rick now believes the optimum waking time is the first three hours after the sun comes up.

"Now I live the athlete's schedule. You don't need to be up all night to be creative."

We pull up to my hotel.

"Okay, so I'll see you at 8:30 and you can see my workout routine. It goes up to 11 am and then we can do some pool work. Then we can grab some breakfast, and maybe we'll go paddle-surfing, and then we can talk and listen to some music."

I'm exhausted just listening. I get out of the car. Rick Rubin moves, pantherlike, into the front seat, and the Rover takes off. You heard me. Rick Rubin moved just like a panther.

A few hours later, it's wake-up time. I'm trying to keep up with the Range Rover as it barrels along a Malibu canyon road. This time Rick is driving, much to the chagrin of a cyclist who gets a close shave and flips the bird at the man responsible for the Beastie Boys. Rick doesn't seem to notice.

We pull up to a modern white mansion. Rick is in the same white T-shirt and black shorts. This being Malibu, he doesn't train with some anonymous guy catering to sagging trophy wives. No, Rick Rubin's personal trainer is extreme surfer, paddleboard evangelist, and shiniest-teeth possessor Laird Hamilton.

They met, of course, through mutual friend Kid Rock. We walk around to the back, past a giant pool, and into a posh, spotless gym. Donovan sings about Jennifer on the stereo. The vibe is groovy-jail. Hamilton's tractor-beam smile and Rasputin eyes immediately suck us in.

"Hey, man," Rick says. "Anything special on the menu today?"

Laird smile-snarls.

"Oh, yeah, a hundred reps."

Rick is confused.

"Of what?"

"Everything!"

Rick's face falls for a moment.

"That's the same look everybody gave me when I told them! Get to work!"

There are some distractions. A few feet away, John C. McGinley of Scrubs is kneeling on a giant exercise ball and juggling while staring at himself in the mirror. Rubin gets to work, and Hamilton offers me a beverage.

"It's air water. It's made by a machine that sucks water out of the air."

Air water tastes like stink water. Rick stretches for a while, then stands barefoot on golf balls and does arm curls with light weights. His feet slip and slide as he lifts. Hamilton thinks the balancing keeps Rick engaged.

"If you're doing just curls, you start zoning out," says Hamilton. "Routine is the enemy." We talk about Rick as if he's not there, but he's here, at our feet, doing a hundred push-ups. Then he's behind us, doing a hundred sit-ups on the McGinley ball.

"A lot of these exercises come to me in dreams," Hamilton says.

Rick's white T-shirt is soaked, and sweat rolls down from the black shorts. He is smiling. Hamilton fiercely nods approval.

"No one does what he's done in his life without having focus and drive," says Hamilton, speaking more intensely than is humanly possible. "He's just implemented the discipline that he used to make a great album to remake his physical health. This isn't just about Rick losing weight. It's about the transformation of his personality."

Hamilton excuses himself to do some other Superman-like tasks on his daily agenda. Rubin points toward the pool.

"You ready to get in?"

Now the shorts make sense! By the time I've changed, Rubin has removed the cover of a 25-meter pool and slipped a swim mask over the non-bearded portion of his face. He tells me we're going to walk slowly with 10-pound weights in each hand into the deep end.

"See how far you can get."

It seems simple. We get halfway across to where the water is eight feet deep. Bouncing up to the surface for air. Soon, I have to drop the weights at the bottom and fly up for air. Rubin chides me slightly.

"Don't drop the weights. You have to put them down, or you could scar the pool."

I apologize and suck air. We eventually get to the 14-foot-deep end of the pool.

"Okay, here we pick up the weights from the bottom, jump-swim to the top, and then dive back down with the weights."

This seems simple. Then I try it. I manage to do two of them. I grab the side of the pool gasping while Rick goes up and down with the optic yellow weights. He does it for 15 minutes and isn't winded at all.

"The water was the best thing for me," he says. "In the gym, I was so weak – the guys can lift hundreds of pounds more than me. Out here, the difference wasn't so great. I do this with 10-pound weights. Laird does it with 20 pounds."

We dry ourselves and drive off for some breakfast. Howard Stern is blasting from the stereo. "Do you listen to Stern? He's gotten funnier. And less mean."

We arrive at Coogie's Cafe, a regular Rick hangout. Rubin orders first: "I'll have four eggs, with asparagus, broccoli, kale, zucchini, basil, tomatoes and onions, peas, olives, spinach, no mushrooms, double veggies. Well-done on the eggs, scrambled, side of salsa and side of guacamole, red bell peppers."

I order three eggs scrambled with cheddar.

The waitress has a question.

"Are we using your eggs for both?"

Rick says yes. The waitress walks away, and he explains.

"I use special eggs. They're better. Organic, super-duper eggs. From Santa Barbara. I got four dozen because I'm here a lot."

A few minutes later, the eggs arrive. Famished from my two reps, I dive in, but Rick pokes at his plate and furrows his forehead. He calls over the waitress.

"I think there's cheese in my eggs. It tastes like there's cheese."

Rick Rubin eats no cheese. The waitress goes for the manager, who runs into the kitchen and then over to our table.

"I checked with the cook. No cheese came close to your eggs. We know how important that is."

Rubin's concern lifts, and he smiles. He gives a seated version of the Buddha bow. He begins to eat and then asks me a question."

How are your eggs? Amazing, right?"

It's easy to forget that today is a workday and organic egg–eating Rick Rubin is the head of a record label. He took the job four years ago when the music industry was flatlining. The era of the album was dead. Record execs were desperate, so desperate that Columbia hired him as co-chairman with terms that give unconditional surrender a bad name.

Their new hire was free to keep producing other artists whether they were on Columbia or a competitor. He would never have to come to the office or even have an office phone. However, he stipulated that Columbia move the office he would not frequent from Santa Monica to a more – according to Rick – karma-cool I.M. Pei–designed space in West L.A.

He flashed a vexed look when I asked about the move. "Wouldn't you want to get out of a space with bad memories and go to a place full of promise and happiness?"

Hiring Rick Rubin wasn't a foolish idea. In the 1980s, he started Def Jam with Russell Simmons and then ran Def American Recordings after he and Simmons had a falling-out. In 2007, the 'New York Times Magazine' put Rick on its cover and grandly asked, "Can Rick Rubin Save the Music Business?"

The answer turned out to be a resounding no. In his first three years on the job, Rick Rubin produced bands that have sold eight million units, but only 1.5 million of them were for Columbia. The ledger is balancing out this year, with the multiplatinum sales of Adele's 21 – largely produced by Rubin. But his connection to Columbia is vague. He hasn't left the company, but his phone doesn't ring very much.

"The job isn't complicated," says Rick. "Help good bands do great work. I have no interest in fighting. If someone brings me in to help make a change and inspire and make things better, I'm down. If someone brings me in to do that and then doesn't want me to do that, well, that's okay, too."

I asked him if that was what had happened at Columbia.

"It hasn't been completely open-minded." He then tries to turn his frown upside down. "In some ways, not having free rein to do what needs to be done at work allowed me to do the physical transformation. I have all this energy for positive change. I'm in a situation where I'm under contract to do this work that often people don't like me to do."

No one has ever described a corporate freeze-out in such a benign way. It's now noon, and Rick's breakfast plate is clean.

"You ready to go paddle-surfing?"

Rick has boards already down on the beach. It's a little choppy, and his instructions are basic: "Okay, you want to get your board parallel to the waves, distribute your weight evenly, and paddle with your elbows locked." That's it.

We walk the boards down to the water. Next thing I know, I'm being toppled by two-foot waves and Rick's nowhere in sight. Oh, there he is, 50 yards out to sea! He has a giant smile on his face, his beard trailing behind him. Rick gives a friendly wave and keeps paddling.

I don't take this personally – this is how he works with bands, too. They talk out songs and then he disappears, only popping in when the band is playing live and for the vocals. Some bands love it; some feel abandoned. Twenty minutes later Rubin sails into shore. I've made no progress except for a slew of bruises on my shins.

He makes an observation. "Maybe it was too windy for your first time."

We hoof the boards back up the beach. He is far ahead of me. I think of Brian Wilson's intense and short-lived health kicks of the 1970s. I ask him if this pace of physical exertion is sustainable for the rest of his life.

"Sure, I'd have to go back to being a totally different person to go back to my old ways. I like who I am now. I would never go back."

But people get tired of their gurus. Wilson eventually got free of his, Dr. Eugene Landy, sick of his mind games and tendency to take songwriting and production credits. Laird Hamilton is famous in his own right, so don't look for him playing percussion on the next Rubin-produced Metallica record, but he seems omnipresent in Rubin's life. We head up the beach, and a muscled middle-aged man appears in front of us. Another Hamilton disciple, he's carrying a 100-pound stone ball. Rubin is intrigued."What's that?" "It's Laird's latest torture device. You pick it up and throw it. That's it." Rick bends at the knees, lifts the orb, and staggers backward. This looks like it's going to end very, very badly. But he regains his footing and tosses the ball onto the hot sand. He's sweating and grinning.

"Laird is nuts. But good nuts."

From the outside, Rick Rubin's house above Zuma Beach is a generic millionaire beach home. There's a rarely used tennis court and a circular drive. Inside, a construction crew is hard at work remodeling a wing of the house. Incense burns.

"I wanted it to be simpler and more open. So I'm turning seven bedrooms into three."

Up the stairs we go. The master bedroom is a new-age space pad. Everything is white.

The white bed is on the white floor. Two nightstands hold identical glass bottles of water in exactly the same spot. There are two giant white beanbag-like contraptions at the foot of the bed. A white tub looks out onto the sea. There's a white toilet in what can best be described as an open floor plan.

"I like things in a certain way. Sometimes I go into someone's office and start rearranging things. Some of them get angry, but most agree that I make the space better."

Rick has never been married and has an unseen girlfriend. ("It's early. I don't want to jinx it.") He owns another mansion in the Hollywood Hills but hasn't slept there in years. We wander into an open room with giant speakers and reams of cable. Rick used to go to L.A. and New York City to produce and mix, but now he does it from home. Songs are dropped into his top-secret, password-protected hard drive with studio-quality sound.

"It's so peaceful here, it's hard to leave. I used to come to Malibu for exactly six hours a week – that's all I could stand. That's all changed."

Rick checks his inbox with a handheld contraption. There's a new mix of a Chili Peppers song that he wants to listen to. We sit on the couch, and Dave appears with glass bottles of water. Rick hits play. Sound blasts us like a rogue wave. He listens with his eyes shut, nodding his head in bliss-filled harmony. Every minute or so, he opens them and taps on an iPhone. When the song ends, he tugs on his beard and reads his notes aloud:

"First verse, vocals a hair loud, guitar on right, in verse after chorus, too noisy, feels like dynamics could be better, verse to chorus is good, but verses get a bit old musically on the way, last chorus isn't a big enough of a step-up from the rest of the song, percussion on the last chorus seems a bit thin, cymbals can shush more than hiss."

He hits a few buttons, and the file is sent back to the band for further revisions. He and the Peppers have worked together for 20 years, and the band is used to his voice-of-God, ultra-hands-off style. But it's not a method that works with everyone: Both U2 and Crosby, Stills & Nash aborted sessions with Rick. Regarding CSN, the producer shrugs his shoulders and says, "They decided it was too much work. They have a certain way they're comfortable with."

Rick Rubin has a comfort level as well. He goes into a project with a specific idea of what he wants to accomplish, though sales are not one of his concerns. "That's not what I'm about. I try to help artists go into a direction that will help build their careers long-term."

We listen to a few more songs before Dave whispers something in Rick's ear. He sighs. "I have a 3 pm meeting." The part of his face not covered with hair makes a face. "And it's in Los Angeles."

About two hours later, I receive a text: I'm back and ready to talk some more. Come over.

It is now nearly dusk, and a cool afternoon wind blows off Zuma. Dave directs me to a spot on the deck. A moment later, Rick emerges.

"How was the meeting?"

"Ugh. It was a meeting."

His face animates as he remembers something.

"Hey, I wanted to show you those meditation exercises you should do before you get out of bed. The ones Serj was talking about."

We lie down on matching deck chairs. Rick begins working his fingers over his face.

"The first one, you want to pull your fingers on your forehead and then pull sort of hard until your hands are placed kinda hard on your windpipe."

For a moment, Rick watches me to see if I'm doing it right. Obviously I'm not, so he slips into his own reverie. He works through the next three with a dreamy smile on his face. Finally, he sits up.

"This last one is a good one. It's called 'galloping horses,' and you start tapping on your head, working all the way back, from top to back."

He's right! It does seem like galloping horses! Dave returns with a snack of apples dusted with cinnamon. I eat a couple before realizing that Rick Rubin still has his eyes closed. Waves crash, bands beckon, and his record company's future remains uncertain. In a week, he will throw his back out exercising. But right now, the streamlined Rick Rubin is somewhere else, galloping into the future.