Forget the Atkins diet. This weekend, thousands of bicycle riders will consume excessive amounts of carbohydrates to make up for the calories they will burn on the annual Cascade Bicycle Club's Seattle to Portland Bicycle Classic (STP).

More than 11,000 bananas, 4 tons of watermelon, 13,000 bagels and 18,000 sandwiches will be doled out over the 204-mile course by volunteers at designated rest stops.

"I always joke that STP is one of the few cycling events you can do and still gain weight because there's so much food," said Tony DeVita, an avid bike rider and the store manager at Gregg's Bellevue Cycle. "It's just nonstop consumption."

This year marks the 26th annual STP. In all, 8,500 riders from 36 states and a variety of countries were set to take off from the University of Washington's Montlake parking lot at 4:45 this morning. About one-fourth of them will complete the ride in one day.

STP is Cascade Bicycle Club's largest fund-raiser. At $80 a head, the organization expects to raise $680,000 in registration fees.

The average STP rider (150 pounds) will burn about 3,900 calories on the road, said Carry Porter, marketing director for Cascade Bicycle Club. In contrast, Lance Armstrong would need to eat 541 Hostess SnoBalls to replenish the 97,380 calories he will burn during this year's 2,241-mile Tour de France race, according to the August issue of Bicycling magazine.

The first food stop on the route, Le Cafe de REI, is modeled after the famous French race. Riders will be greeted at mile 24 by 100 beret-wearing volunteers from longtime sponsor Recreational Equipment Inc. (REI).

"We do it every year to give back to the cycling community," said Will Chin, REI events administrator, who rode his first STP in 1986."We try to make it fun."

As also the most elaborate stop, Le Cafe de REI in Kent boasts free massages in addition to tons of food. Complimentary water and mechanics also will be available. Cascade Bicycle Club anticipated that about two-thirds of the riders will stop there.

"The important thing, whether it's at mile 24 or at mile 200, is to keep your body hydrated and fed," Chin said.

Some participants use the ride to raise funds for charities, and the event's dedication to philanthropy and health inspires many businesses, and executives like Chin, to volunteer time and services.

Whole Foods donated organic food, much of it fresh produce trucked in from California, for three of the five major food stops.

Yesterday, volunteers at Spanaway Junior High in Tacoma unloaded two semitrailers filled with grapes, watermelon, energy bars and more.

Peanut-butter-and-jelly sandwiches are the most popular item, said David Holbert, marketing and community-relations specialist of Whole Foods. He estimated that all 5,700 organic peanut-butter-and-jelly sandwiches, each about 400 calories, would be devoured along the way.

When Seattle-to-Portland began in 1978, there were half as many sponsored stops. It has been run annually, except in 1980 when Mount St. Helens erupted, closing some roads and covering part of the Northwest with a layer of ash.

Lara Bain: 206-464-2112 or lbain@seattletimes.com