Energy expenditure of elite female runners measured by respiratory chamber and doubly labeled water.

To determine whether female athletes have unusually low energy requirements as suggested by many food intake studies, energy expenditure (EE) and intake were assessed in nine elite distance runners [26 +/- 3 (SD) yr, 53 +/- 4 kg, 12 +/- 3% body fat, and 66 +/- 4 ml.kg-1.min-1 maximal O2 uptake]. Subjects were admitted to a metabolic ward for 40 h during which 24-h sedentary EE was measured in a respiratory chamber. Free-living EE was then assessed by the doubly labeled water method for the next 6 days while the women recorded all food intake, daily body weight, and training mileage (10 +/- 3 miles/day). Energy intakes estimated from free-living EE (2,826 +/- 312 kcal/day) and body weight changes (-84 +/- 71 g/day) averaged 221 +/- 550 kcal/day in excess of those calculated from food records (2,193 +/- 466 kcal/day). The energy cost of training (1,087 +/- 244 kcal/day) was calculated as the difference between free-living EE and 24-h EE in the respiratory chamber (1,681 +/- 84 kcal/day) corrected for the thermic effect of food of the extra energy intake. These data do not support the hypothesis that training as a distance runner results in metabolic adaptations that lower energy requirements in women.