Los Angels Times via AP – Phil Keoghan, he of the arched eyebrow and host of Emmy Award-winning “The Amazing Race,” is a self-acknowledged creature of extremes.

For his day job, the 41-year-old New Zealand native logs more than 400,000 air miles per year, mostly as he crisscrosses the globe with the CBS show’s $1-million prize and adventure-hungry contestants. But that’s nothing, really. He’s also putted his way—roughly 12,000 golf strokes and 107 miles in all—across Scotland, set a world record for bungee jumping, eaten a fancy meal atop an erupting volcano and earned a reindeer-racing license in Finland.

This image provided by CBS shows Phil Keoghan, right, host of CBS’s The Amazing Race, kicking off his 40-day, 39-city, cross country bike “Ride Across America” on Saturday, March 28 from Santa Monica, Calif., with the support of local National MS Society members. Keoghan is riding across the country from Los Angeles, Calif. to New York City. Other riders are unidentified. (AP Photo/CBS, Rudi Simpson)

Starting Saturday, he’s going to be facing another extreme: a 5,000-calorie-per-day diet featuring an afternoon treat he calls a “Philiminator” Shake (a special energy concoction combining whey protein, soy milk, flax seed and peanut butter). He’s going to need every ounce to fuel a 40-day, 3,500-mile bicycle ride across America that kicks off from Santa Monica and, he hopes, will end in New York City by early May, days before the season finale of “The Amazing Race.”

The bike ride, during which he will cycle as many as 100 miles per day, has two major purposes: to promote the reality show and help raise money and awareness for the National Multiple Sclerosis Society. Fans of the show are invited to ride along with him for some of the journey. (See www.philridesacrossamerica.com

for details.)

And then there’s that extreme thing going on inside him.

“What drives me is really my will to live,” said Keoghan, who had a near-death experience when he was 19: He almost drowned while diving inside a shipwreck. “I’m inspired by people who seek to squeeze the lifeblood out of life. I just have this overwhelming desire to take as much of the opportunity to live as I can because you look around you and you realize a lot of people are already dead.”

Keoghan has been an avid cycler for years, averaging about 12 hours a week on a bike, and he also has been active in Bike MS, a nonprofit organization that has raised nearly $700 million to support the fight against the crippling disease that attacks the central nervous system. (Keoghan has a cousin with MS.)

“The sad part of it for me is that it takes movement away from people, and I treasure being able to move so much,” he said one recent afternoon while taking a break from postproduction work in Hollywood. “It just breaks my heart that they get this gift taken away from them.”

His biking adventure will roll through what reads like a tour schedule for a rock band. There are 39 stops in cities that include Las Vegas, Denver, Omaha, Neb., Chicago, Pittsburgh and Washington, D.C. The hardest stretch is expected to be between Los Angeles and Denver. Even if it doesn’t snow, he must get through three mountain passes higher than 10,000 feet.

“Economically, environmentally and health-wise, it just seemed like riding a bike makes a lot of sense,” said Keoghan, who will be accompanied by a logistics team that includes his father, who won a mini-following after appearing on his son’s reality show last year.

Keoghan’s fascination with extreme activities may seem at odds with his on-screen persona. On “The Amazing Race,” the host is calm, collected and nearly unflappable, in contrast to his contestants, who hyperventilate their way to each week’s finish line. And save for the occasional flash of wry humor—communicated mostly via the raised eyebrow—he’s a quintessential straight man.

But in person, he’s animated and energetic—two qualities that should come in handy on his long road trip.

“The persona thing is really interesting,” Keoghan said with a laugh. “I remember once I sent a funny reply back to someone who had e-mailed and they said, ‘Oh, my God, you do have a personality.’”