Total free living energy expenditure was compared in lean and obese women by the new doubly labelled water method and partitioned into basal metabolism and thermogenesis plus activity by whole body calorimetry. Average energy expenditure was significantly higher in the obese group (10-22 versus 7-99 MJ/day (2445 versus 1911 kcal/day); p<0-001) resulting from an increase in the energy cost of both basal metabolism and physical activity. Self recorded energy intakes were accurate in the lean subjects but underestimated expenditure by 3-5 MJ/day (837 kcal/day) in the obese group. Basal metabolic rate and energy expenditure on thermogenesis plus activity were identical in the two groups when corrected for differences in fat free mass and total body mass.In the obese women in this series there was no evidence that their obesity was caused by a metabolic or behavioural defect resulting in reduced energy expenditure.

Energy intakes assessed by 7-d weighted dietary records (EI-WDRs) and diet histories (EI-DHs) were compared with concurrent estimates of total energy expenditure (TEE) by the doubly labeled water method in 78 subjects aged 3-18 y. EI-WDRs were not obtained from the 3- and 5-y-old subjects. EI-WDRs in the 7- and 9-y-old children were 108 +/- 25% (n = 12) and 97 +/- 15% (n = 12), respectively, of corresponding TEE values showing good agreement. However in the 12-, 15-, and 18-y-old subjects EI-WDR averaged 89 +/- 12% (n = 12), 78 +/- 18% (n = 12), and 73 +/- 25% (n = 10), respectively, of corresponding TEE values. The difference was greater than or equal to 20% in 13 adolescents. Mean EI-DHs were 114 +/- 19% (3 y), 111 +/- 19% (5 y), 111 +/- 23% (7 y), 106 +/- 9% (9 y), 114 +/- 17% (12 y), 101 +/- 21% (15 y), and 98 +/- 21% (18 y) of TEE estimates. Differences were significant in the 3-, 9-, and 12-y-old subjects. Results suggest that 7-d EI-WDRs tend to underestimate food intake of adolescents. Although EI-DHs were biased towards overestimation in most age groups and individual measurements lacked precision, EI-DHs were more representative of habitual intake than were EI-WDRs.

1. Body composition was assessed in 28 healthy subjects (body mass index 20-28 kg/m2) by dual-energy X-ray absorptiometry, deuterium dilution, densitometry, 40K counting and four prediction methods (skinfold thickness, bioelectrical impedance, near-i.r. interactance and body mass index). Three- and four-component models of body composition were constructed from combinations of the reference methods. The results of all methods were compared. Precision was evaluated by analysis of propagation of errors. The density and hydration fraction of the fat-free mass were determined. 2. From the precision of the basic measurements, the propagation of errors for the estimation of fat (+/- SD) by the four-component model was found to be +/- 0.54 kg, by the three-component model, +/- 0.49 kg, by deuterium dilution, +/- 0.62 kg, and by densitometry, +/- 0.78 kg. Precision for the measurement of the density and hydration fraction of fat-free mass was +/- 0.0020 kg/l and +/- 0.0066, respectively. 3. The agreement between reference methods was generally better than between reference and alternative methods. Dual-energy X-ray absorptiometry predicted three- and four-component model body composition slightly less well than densitometry or deuterium dilution (both of which greatly influence these multi-component models). 4. The hydration fraction of fat-free mass was calculated to be 0.7382 +/- 0.0213 (range 0.6941-0.7837) and the density of fat-free mass was 1.1015 +/- 0.0073 kg/l (range 1.0795-1.1110 kg/l), with no significant difference between men and women for either. 5. The results suggest that the three- and four-component models are not compromised by errors arising from individual techniques.(ABSTRACT TRUNCATED AT 250 WORDS)

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In patients with HIV infection, total energy expenditure is reduced during episodes of weight loss. Reduced energy intake, not elevated energy expenditure, is the prime determinant of weight loss in HIV-associated wasting.