RESUMO
Doubly labelled (2H2(18)O) water was used to determine the daily total energy expenditure (TEE) in the free living state of 6 adult, healthy, weight stable, male volunteers over a period of 21 days. The body weights of the subjects ranged from 42.3-70.4 kg. Isotope pool sizes and elimination rates were calculated from 18O and 2H enrichments in basal and daily (21 days) post dose urine samples using the multipoint slope intercept method after corrections for isotope fractionation. The physical activity level (PAL) of the subjects was also measured during the experiment as the ratio of measured TEE to measured basal metabolic rate (BMR). Simultaneous prediction of the total energy expenditure was also carried out by combining the measurements of BMR by indirect calorimetry, and daily physical activity level by 7 day recall. TEE calculated by the isotopic technique was 9.35 +/- 2.00 MJ/day, with an inter individual variation of 21.4 per cent. The measured BMRs in the subjects along with PALs obtained by recall, gave a total daily energy expenditure of 8.66 +/- 2.20 MJ/day with an inter individual variation of 25.4 per cent. The average BMR was 5.59 +/- 0.99 MJ/day and the average PAL (by recall) was 1.54 +/- 0.12. The inter individual variation of the BMR was 17.7 per cent and that of the recalled PAL was 7.9 per cent; the latter increased to 12.2 per cent when the PAL was calculated from the ratio of the measured TEE to the BMR. There was no significant differences between the methods (isotopic and predicted by BMR), although, the TEE obtained by the isotopic method was higher, by about 0.7 MJ/day, or 7.9 per cent, than the TEE predicted by BMR.