A high-carbohydrate diet runs counter to popular diet gospel right now, but nevertheless, thousands of people around the Valley are piling their plates with pasta and potatoes this week.

If you’ve talked to anyone training for the Rock ’n’ Roll Arizona Marathon on Sunday, you might have heard them talk about "carbo loading." Marathon runners, distance cyclists and other endurance athletes know the benefits of a temporary increase in carbohydrate consumption in the days leading up to events.

"Carbo loading is the act of eating a lot of complex carbohydrates before a big race in order to store up as much energy as your body can hold," said Brian Collins of Mesa, owner of 1st Marathon (www.1stmarathon.com). "It’s like setting off on a trip in your car. You don’t start your trip on a quarter tank."

Collins, whose business trains people to run their first marathon or triathlon, says complex carbohydrates are the best fuel for the body before an endurance event. Good sources include pasta, whole grain or brown rice, black beans, potatoes and breads. These burn slowly, like putting a large log on a fire, he said.

But carbo loading must be done correctly.

"One of the big mistakes a lot of first marathoners make is they carbo load one time," Collins said. "They have this giant meal right before the race."

The right way to do it, he said, is to gradually alter your diet about a week ahead of a race so that more and more of your calories come from carbs.

"Don’t overeat," he said. "Just shift calorie consumption."

People must carbo load safely, said Kathleen Woolf, assistant professor in the department of nutrition at Arizona State University East. In the 1960s, she said, some athletes would get 90 percent of their calories from carbs, and they’d experience low blood sugar and an increase in injuries. The modified regimen prescribes 50 percent of calories from carbs for three days, then about 70 percent for three days, and one day of rest before a big event.

Woolf said a safe carbo loading program is essential for endurance athletes.

"Research after research shows they can improve performance, they can improve their power and their speed," she said.

If you haven’t already tried carbo loading and you’re planning to run this weekend, don’t do it now, Woolf warned. Athletes should experiment with carb loading well in advance of a big event, because they may find their leg muscles become heavier from all the extra glycogen being stored. (The body stores carbohydrates as glycogen in the muscles and liver and converts it to glucose to use as energy.)

Whether you’re ready to ramp up those carbs or just want to buck the Atkins trend (a controlled carbohydrate approach to nutrition pioneered by the late Robert C. Atkins), turn to page D6 for some carb-crazy recipes to try.