Following up... I asked Max Testa about this topic today. Much of this has been mentioned or is known already but I'll summarize it anyway to confirm some opinions. Pros can race at "very high intensity" using fat (especially tryglicerides) for fuel. They can do this much better than a decent amateur cyclist. This ability can be trained with a focus on certain kinds of aerobic capacity intervals in addition to the widely-used "LSD" training. Another way they improve this ability is sometimes on the day after a hard race they will have no carbs for breakfast, just fats, protein, and fluids and then go out for 3-4 hours at medium pace. He wasn't sure how much bodyfat vs. eaten fat was used during races but the best pre-race meals are somewhat high in (good) fats. The problem with the fats that many riders eat during the race is they are often bad fats. Ham and cheese sandwiches are not the majority of what they eat during races. Fats help slow down the release of energy from the digestion of sugars. Too much sugar/carbs before and during the event causes digestion problems and rapid releases of sugars which can also encourage too much lactate production. Insulin response is very important. When there is a surge of insulin the muscles "open up" and it is easier for sugars to be stored and I think he said protein can get to the muscle easier. Back when insulin was not on the banned list the teams he worked with used insulin injections for these reasons. Eating small, frequent meals not only stabilizes blood sugar levels but over a period of several months of some proper training for this ability the insulin response to blood sugar increases will change slightly. By minimizing the need for insulin during the day we can generate a very strong insulin response when we need it. Drinking or eating very high sugar right after training is very, very important to generate a strong, beneficial surge of insulin. Many riders report that they feel especially good 1-2 days after they "bonk" i.e., run out of glycogen during a ride. This is because significant amounts of growth hormone are released as a protective measure by the body and to help convert fats to fuel. (Another reason why hGH is being used by some athletes?) Race food is about 25% of total food eaten during a stage race. Breakfast is relatively high protein and fat, with carbohydrate. When Andy Hampsten first came to the team (7-11) he was eating oatmeal and pasta for breakfast and 90 minutes into the race he was looking around for more sugar. Eventually he learned to eat something like a chicken breast with an egg on top before races and he did much better. They will use IV's during stage races to replace mostly fluids. They don't want too much fluid in the stomach because it dilutes the digestive fluids needed to digest all the food they need to eat. Running out of bodyfat stores during a stage race is usually not a problem but they watch closely to make sure the riders are eating enough. They don't keep track of % of fat, carbs, protein but several years ago they did and it varied between 55-65% carbs, with Northern Europeans likely to have more fat and protein than the others. This is all I remember from the 5 minutes or so that we talked about this topic. -WG P.S. When Eric Heiden was an Olympian his VO2 max was 84 and he weighed 185lbs. That's really high for someone his size.