Still, some of the cyclists actually shed pounds during the Tour.

Mint and melon coulis with blueberries and raspberry and praline #TDF2014 #killerdesert pic.twitter.com/uKUenV0TgH

— Sean Fowler (@Larryvich) July 21, 2014

Keeping up with the energy demands of the race is a balancing act. Mitchell says 350 calories is about as much energy as an athlete can absorb in one hour, and yet the cyclists are burning up to 1,000 calories an hour — as some of them surely did during Tuesday's arduous 148-mile ride through the Pyrenees. It's the first of three days in the mountain range and one of the hardest days in the whole race.

"The body uses fat stores while the guys are riding," Mitchell says.

By the end of the day's ride, the cyclists have built up a major calorie deficit. Back on the bus, they eat boiled potatoes, rice, canned tuna and capsules of fish oil as they're driven to the next hotel.

When they arrive, they dig into a 2,000-calorie dinner, always heavy in meat, fish and other sources of protein — important for helping repair and rebuild the athletes' stressed muscles — followed by a fruit-based dessert. Before bed, the cyclists eat a bowl of cereal or yogurt. A few hours sleep is the only break they get from this demanding schedule of eating, Mitchell says.

Calories should come from the right mix of sources: fat, protein, carbs and on good days, a little alcohol. "Traditionally, if you win a stage, you have a bottle of Champagne," Mitchell says.

Chefs face challenges in cooking for cycling teams, as there may be competitors from multiple nations, each with their own preferences. Mitchell says this year's Team Sky cyclists hail from South America, North America and Europe. (This year, there haven't been any major disagreements over food, he says.)

Sports physiologist Allen Lim has worked with Tour de France cyclists since 2005 and makes natural-ingredient sports drinks at his company Skratch Labs. He says a good chef knows each rider's tastes: what foods they like, what they hate and what they won't eat for health or ethical reasons.

Sometimes, Lim says, the dietary choices of the riders prove too challenging — or annoying — for a team's chef. In 2008, when Lim was traveling with the Garmin team, all the cyclists decided they would ride the race on a gluten-free diet. The chef — a Frenchman — wasn't happy about this.

"He was angry that the guys wouldn't eat pasta or bread," Lim recalls.

The Garmin team now works with chef Sean Fowler, an American who lives in Spain. Fowler has been more willing to experiment with fusion recipes and some gluten-free items, Lim says.

Baked stuffed zucchini with caramelized onions and cabbage topped with goat cheese #TDF2014 pic.twitter.com/ELMnIfvXaR

— Sean Fowler (@Larryvich) July 15, 2014

Fowler is tweeting his culinary wins on the tour, like gluten-free toast with salmon caviar, baked salmon with avocado mousse, gluten-free coconut cake with sheep's milk yogurt and baked curry with marinated turkey skewers and prunes.

While nutritionists like Mitchell accompany the teams to help direct meal prep and make sure all essential vitamins, minerals, fatty acids and other nutrients are served in adequate proportions, Lim says many teams have also hired chefs.

"Unless the cyclists love what they're eating, unless they can celebrate dining with one another and enjoy what they're eating, then they just won't perform," Lim says. "If the food is bad, they won't ride well."

Staying hydrated is important, too. Lim says there was once a prevailing element of machismo among some professional cyclists who abstained from drinking water as long as possible during a hard ride. Now, they've wised up, he says, and may drink well over two gallons of water and hydrating energy drinks per day. When nature calls during the race, they make a gentlemen's agreement to pull over all at once, drain their bladders and get back on the bikes when all are finished, Lim explains.

But there is one thing just as important as eating, Lim says: showering.

"When these guys are done each day, they're so freaking dirty," he says. "They have road dirt all over them. Before eating, they need to wash off." Showers, he says, are provided at each team's finish line station. "If they don't shower right away, it can make them very susceptible to getting sick."

Alastair Bland is a freelance writer based in San Francisco who covers food, agriculture and the environment.

Copyright 2014 NPR.

Sean FowlerSean Fowler

The Epic 2,200-Mile Tour De France Is Also A Test Of Epic Eating