At rest, we all burn roughly 90 calories an hour, or a little more than 2,100 a day. Run at full-tilt on a treadmill for an hour, and you'll burn some 600 – although most of us can keep it up for half of that time. Ride in major cycling race like the USA Pro Challenge or Tour de France, on the other hand, and you'll find yourself burning a whopping 1,000 calories per hour – for four hours a day. Indeed, the Tour is a race on the road and at the table, given that the average racer needs to ingest some 8,000 calories a day in order to keep weight.

Without practicing, it's impossible to keep all the food you need in a day down, says Austrian sports nutritionist Judith Haudum, who is responsible for feeding the BMC Racing Team. "During training, you need to find out how much carbohydrates your body can handle," Haudum says. "If you consume too many in an hour, you run the risk of having to throw up." During the race, riders get about 1,500 calories – primarily from sports drinks, bars, gels, and paninis – still leaving a 6,500 calories deficit. Haudum helps the team close this gap with an early breakfast about three to four hours before a stage. A post-breakfast snack will bring the day's calorie total to more than 1,000 before the race starts. After the race, each cyclist needs to consume the remaining 5,500 calories with several snacks and dinner.

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In the days before stage one, Haudum says cyclists focus on filling their glycogen stores to prepare for the start. For some riders, that means eating up to 800 grams of carbs during that period – or the equivalent of 30 plates of pasta over the course of 48 to 72 hours. "It's eating a lot of food, but you also have to take into account that eating carbohydrate-rich foods, like honey, can help it add up," she says. "It's not that you necessarily have to eat 10 plates of pasta at lunch to meet the carbohydrate needs."

Without such massive quantities of food, riders would be at risk for extreme weigh loss and simply would not be able to compete. "You could have the best massage or have the best bike, but if your body doesn't get the fuel it needs – you can't perform," Haudum says. "That's just the case."

An Example Race Day Food Diary

Breakfast (3-4 hours before the race starts):
1 bowl of porridge (150 calories per cup, cooked) with banana (105 calories per banana), and some nuts (529 calories per cup of almonds)
1 big plate of pasta (174 calories per cup)
1 piece of cake (roughly 225 calories)
Coffee (1 calorie per cup)
Fruit juice (122 calories per serving)

Post-breakfast snack:
Cereal bar (about 120 calories)
Fruit juice (122 calories per serving)

During a 4-hour stage: (quantity varies depending on the stage profile, and weather)
3 gels (about 100 calories each) 1 bar (about 220 calories)
2 paninis (roughly 380 calories each)
8-12 bottles of sports drinks (50 calories per 8 ounces)

Post-race:
Recovery drink (209 calories per cup of chocolate milk)
1 bowl of rice (216 calories per cup) with ham (203 calories per cup) and parmesan cheese (22 calories per tablespoon)

Pre-dinner snack:
Greek yogurt (100 calories per container) with granola, (280 calories per cup)
Dried fruits (roughly 100 calories per ¼ cup)
Water (0 calories)

Dinner:
Salad
Risotto, (about 280 calories per serving) with:
-chicken breast (500 calories per breast)
-vegetables (50 calories per serving of broccoli)
-potatoes (163 calories in a medium-sized potato)
Fruit salad (about 74 calories per cup)

Post-dinner snack:
Fruit (105 calories in a banana)
Crackers (about 13 calories per cracker)