Out of town? Try Hollywood. He was called there at the behest of actress Halle Berry, who had heard of the magic he'd done helping actors slim down for film roles, including Jim Caviezel (The Passion of the Christ) and Milla Jovovich (Resident Evil). Pasternak's job was to help Berry squeeze her frame into the skin tight Cat Woman suit. It was just going to take five weeks, he figured. Really.

Before long, however, word leaked out about the brainy-and-brawny Canadian trainer who rapidly transformed Berry into a superhero-worthy body by using short workouts that suited filming schedules and five meals a day that could be fixed quickly and were small enough to fit into a mini-bar fridge. The Hollywood machine kicked into gear. He appeared on Oprah. Orlando Bloom called. So did Jessica Simpson. Brendan Fraser wanted in, as did Seth Rogen, Katherine Heigl, Robert Pattinson, Hilary Duff, and Miley Cyrus.

Six years later, Pasternak, 35, does get back to his house in Toronto, but only to visit friends and family.

"Next thing I knew, I had the largest celebrity client list in the history of the business. I mean, there's no agent with a roster of celebrity clients like I have," he says proudly.

"It's the strangest thing, because it wasn't contrived," he marvels, then paraphrases his favourite passage from Victor Frankl's Man's Search for Meaning in which he muses that success follows from pursuing a course greater than oneself. "I was just trying to be the best I could be."

That effort has since grown into the Harley Pasternak Inc. empire.

"Don't call it an empire!" he exclaims. "Empire sounds so evil and diabolical!"

Based on Pasternak's best-selling 5-Factor Diet book -- now in 10 languages -- he now sells 5 Factor nutrition bars, DVDs and healthy snack foods on the Shopping Channel, a 5-Factor Licious Living meal delivery program in Los Angeles, Toronto and Vancouver and has trainers in three cities.

"I plan the food nutritionally for myself and if other people like it, that's great. Really, my clients are the guinea pigs," he says, excusing himself from the interview briefly to confer with a colleague about a meatball and pasta dish. ("Is it too garlicky?" he wonders. "I don't know, but I like it.")

In March, Pasternak will announce a greater presence in Canada through a deal with GoodLife Fitness.

For anyone who hasn't heard the Pasternak message the fundamentals are easy enough to grasp: Eat five small meals based on five core ingredients that take five minutes to prepare and get plenty of exercise. His latest book, The 5-Factor World Diet, builds from there. While travelling with celebrity clients and sourcing meals for them, Pasternak noticed the world's healthiest people - the Japanese, Swedish, Chinese and so on -- had much in common: They eat small amounts of a vast range of whole food (Japanese food guidelines suggest eating 30 different food types daily) and they're profoundly connected to their cuisine culture.

Americans, on the other hand, are "eating themselves to death." And although Canadians are also packing on the pounds, he says, "I wouldn't put the U.S. and Canada together. They're similar, but it's clear there's a difference when you look at the average lifespan of the Canadian versus American."

Indeed, according to the CIA World Factbook, Canada's life expectancy is among the highest, placing ninth with 81.23 years, with the U.S. lingering in 50th place with 78.11 years.

Pasternak places the blame squarely at the altar of American lifestyle, gargantuan portion sizes, which have increased 20% to 50% since 1980, and consumerism that absorbs healthy foreign cuisine, then regurgitates it for American tastes.

"The U.S. is a melting pot so everything that comes here melts into one homogeneous Americanized thing," he says.

Raised in Toronto by a "wonderful, healthy family," his father insisted he do a stint in the family rubber hose factory "to make me see that's not what I wanted to do." His mother Barbara led by example in establishing the non-profit Diabetes Hope Foundation, which supports children and families living with diabetes.

"When both his brothers, Bobby and Jesse, developed type 1 diabetes," says Barbara, "I was very proud to see how committed Harley was to be a true role model for the boys."

It's clear it goes further than that: According to her, the entire family have adopted Pasternak's 5 Factor lifestyle.

It was a long time in the making. Pasternak attended York Mills Collegiate, played hockey and attended the University of Western Ontario, then the University of Toronto, after which he landed a job with the Department of National Defence doing nutrition and exercise research. While there, he established his nutrition business. His two brothers, he says, "are still my best friends," and despite living in Los Angeles, admits he still likes to date Canadian girls.

And despite his success, he's still humble enough to feel astonishment when former U.S. president Bill Clinton asked him to consult on childhood obesity. Even more thrilling, he says, was when the Canadian government asked him to be an ambassador for tourism in the United States.

"I couldn't believe it. You know, I'm based in L.A., but Canada keeps pulling me back," he says. "I'm the proudest Canadian ever."