Energy Expenditure was measured with doubly labelled water technique during heavy sustained exercise with an official finishing team in the Race Across America. Energy Intake was also calculated to produce an energy balance for the race. A team of 4 cyclists (Mean ±SD age: 37+4 yr; body height: 182+8cm; body mass: 80.8+6.6kg) completed the race in a relay fashion. The team completed the race in 6 days 10h and 51min. Total mean energy expenditure was found to be 43401kcals (181711kJ) with a mean daily energy expenditure of 6420kcals (26879 kJ). Total mean energy intake from all food and drink consumed was calculated at 29506kcals (123536kJ) with a mean daily energy intake of 4918kcals (20591kJ). This resulted in a total mean energy deficit of 13878kcals (58104kJ) with a mean daily energy deficit of 1503kcals (6293kJ). The high energy expenditure highlights the need for correct and practical dietary strategies and challenges nutritionists to devise high energy diets that not only contain the correct macronutrient balance, but are also palatable to the cyclists, thus encouraging a high energy intake.