Calorimetric evaluation of the diary-respirometer technique for the field measurement of the 24-hour energy expenditure.

The results of measuring the 24-h energy expenditure by the diary-respirometer technique (factorial method) have been compared to those obtained by direct measurement of heat output and continuous recording of oxygen consumption and carbon dioxide production. Anthropometric and skinfold measurements were used to estimate lean body mass in eight male Asian subjects. They remained for 36 h in a metabolic chamber wearing a calorimeter suit. A ventilated hood and differential gas analysers were used to measure oxygen consumption and carbon dioxide production. While the subjects were sitting inactive, the KM respirometer indicated a mean energy expenditure which was significantly lower than with the calorimeter suit or with the ventilated hood. During exercise on an ergometer at 25 W and 75 W the respirometer gave readings of energy expenditure which were also significantly lower than either the ventilated hood or the calorimeter suit. The daily energy expenditure expressed in MJ for a standard body weight of 60 kg (MJ/60 kg) measured from the calorimeter suit was 9.79 MJ; from the ventilated hood, 9.51 MJ; from the diary-respirometer method, 8.30 MJ. The mean energy intake, measured for 10 consecutive d after the the subjects had left the metabolic room was 7.87 MJ, while during their stay in the metabolic room, their spontaneous intake was 7.74 MJ. The diary-respirometer technique tends to cumulate the errors from an incorrect time and motion recording and the potential lack of representativeness of the measurement of the energy cost of the activities. In the present study, it seems that the discrepancy observed between the results of the different methods can be attributed almost entirely to the underestimation of the energy cost of the activities by the respirometer. Contrary to our expectation the diary-respirometer technique does not seem to overestimate systematically the daily energy expenditure.