Energy balance in endurance-trained female cyclists and untrained controls.

Reports of low energy intakes in trained female athletes imply they have an increased energetic efficiency. To address this question, we determined how energy balance was achieved in endurance-trained females cyclists and lean controls (n = 5 in each group). Daily energy expenditure was measured by using standardized physical activity protocols in a whole room calorimeter on two separate occasions: a cycling day and a noncycling day. Energy intake for weight maintenance was determined by a period of controlled feeding 5 days before and the day of each energy expenditure measurement. Energy balance was achieved in the cyclists on the cycling day while they consumed 2,900-3,000 kcal (their usual condition) and in controls on the noncycling day while they consumed 2,100-2,200 kcal (their usual condition). Total daily energy expenditure was not significantly different between the cyclists and controls on the noncycling day with both groups performing similar levels of activity. On the cycling day, daily energy expenditure was significantly greater in the cyclists vs. controls (P < 0.03) as a result of their greater amount of cycling activity. Components of daily energy expenditure, i.e., resting metabolic rate and thermic effect of food and activity (noncycling), were not significantly different between groups. Overall, we found no significant increase in the energetic efficiency of endurance-trained female cyclists compared with controls.

Comparison of dietary self-reports with energy expenditure measured using a whole-room indirect calorimeter.

In this study we used a whole-room indirect calorimeter to evaluate the accuracy of self-reported food intake. Daily measured energy expenditure was compared with 2 weeks of self-reported food intake. Additionally, oxidation of each macronutrient was compared with its self-reported intake to assess the accuracy of self-reported dietary composition. Participants (23 through 60 years old) were eight dietitians, eight subjects who were trained in keeping dietary records, and eight subjects who were not trained. Physical activity in the calorimeter was matched to usual daily physical activity. Overall, measured energy expenditure was approximately 200 kcal/day higher than reported metabolizable energy intake. However, this was the result primarily of a few subjects whose self-reported food intake was considerably below measured energy expenditure. Subjects who were trained in record keeping did not differ from untrained subjects. Dietitians had the lowest difference between intake and expenditure; none of them had the large discrepancies between intake and expenditure seen in the other groups. In all groups, there was a much greater discrepancy between self-reported intake and oxidation of each macronutrient than between self-reported total energy intake and expenditure.