For endurance athletes, carbo-loading on pasta and bread is as much a part of their sports as spandex and heart-rate monitors. So when Dr. Allen Lim, former exercise physiologist for the Garmin-Transitions pro cycling team, and Jonathan Vaughters, Garmin's founder and CEO, suggested the squad switch to a wheat-free diet, the riders thought they were crazy. "Their first reaction was, 'What? No! We can't race the Tour de France without pasta,' " recalls Vaughters. But the two men were banking on the idea that gluten, a composite of proteins in wheat, is responsible for bloating, stiffness, and gastrointestinal distress – huge performance-hindering problems – and the theory that their riders would recover better from grueling stages by avoiding wheat. Moreover, they knew that the team could get all the carbs they needed by eating other foods.

"I was pleasantly surprised," says Christian Vande Velde, Garmin-Transitions's team leader, who was the first member of the team to experiment with going wheat-free during the racing season. "I just had all-around better digestion, and digestion is the biggest thing in utilizing the energy I consume." Teammate Tom Danielson had a similar experience when he started following the diet during the Tour of Missouri in 2008. "My performance really improved a lot – there was definitely a correlation," says Danielson. "I think that my digestion is better, and because of that my sleep is better and my recovery is better."

The riders' results aren't surprising given the fact that humans are ill-equipped to digest wheat. Besides people who suffer from wheat allergies and celiac disease – an autoimmune condition triggered by exposure to gluten that affects about one in 133 Americans, causing everything from diarrhea to fatigue – doctors and nutritionists frequently see patients who simply feel healthier and more energetic when they're eating wheat-free. That's because, unlike cows, we lack the enzymes in our saliva and stomach to fully break down and absorb gluten for nutritional use, so parts of the protein just get smashed up before exiting to the small bowel in large pieces. More than 50 different types of those fragments have been shown to cause adverse reactions, according to Dr. Michelle Pietzak, a celiac expert at the University of Southern California. "So depending on your genetic makeup, you can have an allergy, you can have celiac disease, or it could be that you're just not digesting it well," Pietzak says. And if smooth digestion seems minor compared with strength and VO2max, think again. "It's a huge deal," says Lim. "It might be the hugest deal."

Since the energy needs of elite athletes such as Vande Velde and Danielson are immense – in the Tour de France, cyclists will eat as much as 8,000 calories daily, or more than three times what a moderately active guy needs each day – following a diet that bans wheat could spell trouble, due to the fact that the grain is a great source of carbohydrates. Carbs break down into glucose and serve as the body's primary fuel during exercise. Excess glucose also gets stored in muscles as glycogen, which provides additional energy during exercise and recovery. Without adequate levels of glycogen, an athlete will bonk.

To make sure that didn't happen, Vaughters hired chef Sean Fowler, a Colorado native who owns a restaurant in Spain, for 2008's Tour. Fowler served poultry and eggs as protein sources, fresh fruits and vegetables for vitamins, and for carbohydrates, he simply switched sources. Wheat-based pasta is the carbo-loading standard mainly because it's cheap, readily available, and easy to cook, but other carbs are just as effective, including rice, oats, corn, and quinoa, a seed that's high in carbs and protein. "Every once in a while they'd be like, 'Bread! We want bread!' " says Fowler. But the cravings passed.

Few of us need as many carbs and calories as Vande Velde or Danielson. But going wheat-free is not like going on the Atkins diet, which famously instructs people to cut most carbs out of their diets in order to lose weight. Athletes need carbohydrates, says Leslie Bonci, a sports dietitian for the Milwaukee Brewers. For active guys, she recommends three grams of carbs per pound of body weight per day. "You have to maintain the energy substrate, or you'll slam into the wall," Bonci says.

Garmin's reliance on vegetables, fruits, lean proteins, and fresh, well-prepared food is universally instructive, as well. Many athletes who stop eating wheat, despite having no real problem digesting gluten, still experience weight loss and performance and digestion benefits from inadvertently dodging other dietary pitfalls. No bread, cookies, or hamburger buns usually translates to less sugar, salt, and processed foods spiked with chemical fillers.

The best part may be that Garmin's wheat-free diet is moderate, a tool for periods of intense exertion rather than a permanent exercise in deprivation. "The gist of it is, if you can avoid it, do," Vande Velde says. The rest of the time, he just tries to eat healthfully, without worrying about gluten. "Believe me, I drink plenty of beer in the off-season."

What's on the Training Table
Keeping gluten-free takes planning, but it's not as hard – or limiting – as it seems. Here's a rider's typical menu.

Breakfast
• Fresh-fruit salad, boiled rice, oatmeal, oat milk, muesli
• Syrups: agave, molasses, honey, maple
• On rest days: hash browns and pancakes made with rice and corn flour
• Eggs with yolk-to-white ration of 1 to 2

Race Snacks
• Lim's rice cakes (sushi rice, egg, tamari, olive oil, balsamic vinegar, and prosciutto)
Clif products (including bars and gels)
• Sean's bars (puffed rice, oats, cashews, and almonds)

Dinner
• Fresh-fruit puree: nectarines, apricots, peaches, and plums
• Sean's salad: fresh mixed greens, sweet onions, garlic, nuts, grated carrots, apples, beets, olive oil, vinegar, and grated parmesan or manchego cheese
• Vegetable and fish paella
• Fresh – fruit cornmeal cobbler

Post-Race Snack (eaten with liquids 15 to 30 minutes after exercise)
• Frittata with potato and onion