The present study was performed in order to determine the reliability of the portable calorimeter. 2. Resting energy expenditure (REE) was measured by two different apparatuses: one was the typical gas analyser, the other was the portable calorimeter. 3. Although there are differences among individuals, unless the subject has been exposed to severe physical activity prior to the measurement, a suitable resting time prior to the measurement of resting metabolic rate is 10 min. 4. For the measurement of resting metabolic rate, fluctuations in respiratory quotient (RQ) are extremely small; there is greater fluctuation due to variations in respiration. Therefore, for the screening of energy consumption, the use of a fixed value for RQ is sufficient when measuring only oxygen uptake. 5. Respiratory fluctuations vary from person to person and it is not possible to make stable measurements in 1 or 2 min. Therefore, a suitable measurement time for resting metabolic rate is from 3 to approximately 6 min. 6. The results indicate that this portable calorimeter is a useful apparatus for measuring REE in the field.
