Celebrity jogging: LA's latest fitness craze combines Hollywood's twin obsessions

We nearly didn't notice Larry King, as he wandered down Beverly Drive clutching a cup of coffee. He looked old and thin, and somehow more vulnerable than the pugnacious chat-show host who invades America's living rooms at midnight.

Cheryl Anker was convinced, though. To her expert eye, that hunched figure on the far pavement was definitely The King, even if he had swapped his trademark tie-and-braces for a jeans- and-denim-shirt combo. She pulled out a digital camera and started "papping". Clickety-click.

"I know it's Larry because he always eats breakfast at Nate'*Al's diner, which is up the road," she explained. "His home's here in Beverly Hills, and he works at CNN in Hollywood. It's the weekend, so he doesn't do a show tonight. He's just taking a walk."

We resisted the temptation to dash across the street and grab a close-up. It was probably the right call. Firstly, the cop down the road could have ticketed us for jaywalking; secondly, Cheryl's class was due to begin at 11am, so she couldn't mess around. Time waits for no man, not even a TV star, in the frenetic world of celebrity jogging.

Yes: celebrity jogging. That's the name of the latest fitness craze to sweep Los Angeles. It's a sport, or rather a hobby, that revolves around a simple format. You dress up in Spandex and grab a camera. Then you lollop around an exclusive shopping district hoping to spot someone famous. If you do, you take a photo. If you don't, you continue on your way, consoling yourself with the thought of burning off those nasty calories.

To the uninitiated, celebrity jogging combines two of the most distasteful aspects of American society. It panders to a vain obsession with trying to keep fit, and encourages a prurient desire to invade the day-to-day life of minor celebrities. To aficionados, however, it's a strangely compelling pursuit. Celebrity joggers collect albums full of snaps like philatelists collect stamps or autograph hunters gather signatures. They learn and refine preferred running routes, and become experts on the shopping habits of the rich and famous. With luck, they also become fitter in the process.

Cheryl Anker is one of the sport's pioneers. Today, she makes a living by introducing paying students to the art of spotting famous people in and around LA. The beginners fishpond in which she conducts her classes is the streets close to Rodeo Drive in Beverly Hills. The area is, of course, America's luxury capital, containing a flagship outlet of every global fashion brand, distilled into a couple of square miles, and resembling a cross between Bond Street and Disneyland. But it is probably most famous as the venue of that extravagant shopping trip by Julia Roberts (using Richard Gere's credit card) in Pretty Woman.

To Anker, it's a district laden with possibility due to its swish stores' typical patrons. Aweek or two ago, she bumped into the comedian George Lopez and his wife outside The Ivy (sister to the London restaurant). They'd just had a birthday lunch. She stopped jogging, chatted, and secured a series of knockout pics. Her greatest ever "spot", however, was Sidney Poitier. "I saw him through the window of Office Depot," she recalls. "He was doing some photocopying. So I ran in to get a proper look. The sales assistant told me he came there all the time, and let me ask if he would pose for me. Normally, I respect people's privacy when they're in a shop. But this was Sidney Poitier, a hero of mine, a legend. And he was happy to be in a picture.

This touches on one of the "ground rules" of celebrity jogging, revealed during Anker's briefing session to the 12 or so mostly middle-aged women who have signed up to her $60 class: if you are inside a store, or on any other form of private property, taking pictures is forbidden. Security guards are liable to descend and "wipe" your camera equipment.

We will jog (or, for the larger participants, power-walk) for roughly four miles, she says. From time to time – particularly if we see someone famous – we will stop. We'll all wear matching lurid yellow T-shirts made from a special material that won't show up sweat patches in the 105F midday heat. Our itinerary passes through Louis Vuitton, Van Cleef & Arpels, and the Four Seasons Hotel, where staff look on, baffled. In Chanel, the party is delayed after one member gets stuck in the restrooms.

Outside The Ivy, on Robertson, meanwhile, we are further delayed by half a dozen real paparazzi hanging around the valet-parking booth. They won't reveal whom they're waiting for. Apparently, this is standard procedure: paps hate "amateurs" for undermining their lucrative market. The presence of just six of them suggests, however, that they're following a very minor star, possibly from the world of reality television.

It's a funny old world, where people pay money to gawp at the rich and famous like animals in a zoo. But it does underlines America's curious relationship with stardom – one that occasionally erupts, such as when surfers on a Malibu beach attacked photographers for stalking Matthew McConaughey in his swimming trunks.

The irony, of course, is that while Americans are often appalled by their feral paparazzi, plenty of them also carry People magazine in their handbag. They don't seem to register a connection, either: look at the OK-reading onlookers in the Malibu "pap rage" videos posted online.

And while LA venerates its celebrities, it isn't always as obsessed by them as you'd think. The celebrity-jogging community, for example, is worryingly thin on fame junkies. Instead, most are regular people like housewife Bonnie Keilband, who says: "I wouldn't recognise a celebrity if I tripped over one," but fancied a change from another Saturday walking her dog.

Anker's tour finishes outside the Sprinkles cupcake store on Santa Monica Boulevard, where she buys her weary, sweaty students a big cake, and hands them a "recovery pack" of fruit, water and energy bars. The morning, we realise, has successfully reflected what LA life is all about: trying to keep fit, scoffing junk food, and having a brief encounter with a passing celebrity.