Energy intake and expenditure in women runners and non-runners were assessed by weighed food records, evaluation of minute-by-minute activity diaries, and indirect calorimetry. All participants were adapted to their stated activity levels for at least 6 months and maintained a constant body-weight throughout their participation. Calculated daily energy intake equalled calculated expenditure in non-runners (7300 (SD 1536) v. 7476 (SD 872) kJ/d), but calculated energy expenditure in women running about 54 km/week was found to exceed intake by more than 2700 kJ/d (8259 (SD 1466) v. 10963 (SD 1367), P < 0.01). The runners showed no evidence of compensating for the increased energy expenditure associated with running by engaging in lower-intensity activities during non-running time. Further, runners did not decrease energy expended at various activities. The findings suggest that women adapted to high levels of activity may possess mechanisms to maintain body-weight without significantly increasing energy intake.
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