ENERGY-METABOLISM IN FREE-LIVING, LARGE-EATING AND SMALL-EATING WOMEN- STUDIES USING (H2O)-H-2-O-18

The doubly-labelled water ((H2O)-H-2-O-18) technique was used to asses s the long-term rates of energy expenditure and, after accounting for any changes in body composition, the derived rates of energy intake in weight-stable 'large-eating' (n 6) and 'small-eating' (n 6) women. Th e self-reported energy intakes (approximately 11.2 v. 5.6 MJ/d) and en ergy expenditures (approximately 8.5 v. 124 MJ/d) for the 'large-eatin g' and 'small-eating' groups respectively, should not be sustainable w ithout significant body-weight changes. (H2O)-H-2-O-18-assessed rates of energy expenditure for the 'large-eaters' (approximately 85 MJ/d) a nd 'small-eaters' (approximately 11.3 MJ/d) were in close agreement wi th the results obtained using 5 d, self-reported activity diaries but the derived rates of energy intake for the 'large-' (approximately 8.5 MJ/d) and 'small-eaters' (approximately 10.8 MJ/d) were markedly diff erent from those obtained using self-reported, weighed food diaries. W hen two 'small-eaters' were supplied with their self-reported energy i ntakes (approximately 5 MJ/d) for up to 28 d both subjects lost about 0.75 kg body-weight/week. These results provide no support for the exi stence of 'metabolically efficient' women in the community.