Like jelly donuts? How about 30 a day? Well, that's the number of donuts you would have to eat to get enough calories to compete for just "one day" during the Tour de France.
Traveling approximately 2000 miles in 23 days, a Tour de France cyclist like Lance Armstrong typically eats the equivalent of 30-32 jelly donuts per day in calories, according to physicist Philip Morrison of MIT. Morrison conducted an investigation of the Tour de France for his 1987 PBS documentary series "The Ring of Truth." (In comparison, a normal adult male eats the equivalent of 12 jelly donuts a day, assuming that each jelly donut is about 250 calories.)
So where do all those donuts go? During a typical day's race, Morrison says, a biker burns off about 1 or 2 jelly donuts worth of energy in overcoming friction and manipulating his bike. Propelling the bike forward in a typical day's race requires only about 6 jelly donuts of energy.
Where do the remaining 25 donuts of energy get spent? You guessed right--it's wasted--in the form of heat. Now, the human body is a relatively efficient machine. But like all machines, it unavoidably generates heat which cannot be employed to perform useful work. This heat--20-25 donuts' worth, according to Morrison--is mainly carried away in the form of sweat created by exertion.
Competitors drink about 4 gallons of water a day, and this water evaporates from their bodies to carry away the heat. What keeps them cool enough to endure the race, says Morrison, is the streaming wind that hits their face.