The present study determined the intra-individual variation of BMR measurements, using a standard out-patient protocol, with the subjects transporting themselves to the laboratory for the BMR measurements after spending the night at home. The effect of a non-fasting state and variation in daily habitual physical activity the day before testing was evaluated. Eight male and eleven female subjects participated in three BMR measurements with 2-week intervals. Physical activity was estimated with a tri-axial accelerometer for movement registration, during the 3 d before each BMR measurement. There were no significant differences in estimated BMR (ANOVA repeated measures, P¼0·88) and in physical activity (ANOVA repeated measures, P¼0·21). Mean within-subject CV in BMR was found to be 3·3 (SD 2·1) %, ranging from 0·4 to 7·2 %. Differences between BMR measurements could not be explained by differences in physical activity the day before; however the mean within-subject CV in BMR changed from 5·7 to 5·2 % after correcting for within-machine variability and from 5·2 to 3·3 % after excluding five measurements because of non-compliance to the protocol including fasting. In conclusion, BMR values measured with a standard out-patient protocol are sufficiently reproducible for most practical purposes despite the within-subject variability in physical activity the day before the measurement. For this purpose, however, non-fasting subjects must be excluded and a regular function check of the ventilated-hood system is recommendable.
Reproducibility: Calorimetry: Body composition: AccelerometerBMR is the main component of average daily metabolic rate. It is defined as the daily rate of energy metabolism an individual needs to maintain and preserve the integrity of vital functions. A measurement of BMR must meet certain conditions. The subject must be awake and the measurement must be performed in a thermoneutral environment to avoid heat production or heat loss for maintenance of body temperature. Furthermore the subject must be in a fasted state (absence of diet-induced thermogenesis) and in rest (absence of activity-induced energy expenditure).Diet-induced thermogenesis is an increase in energy expenditure (EE) above BMR after eating. A 10 -12 h fast before BMR measurements is the accepted procedure followed by investigators to eliminate the thermic effect of food on basal EE. However, the time interval required to eliminate any residual effect of physical activity on BMR has not yet been described in a similar way. Some studies have observed that moderate-intensity physical activity elevates metabolic rate for only a few minutes to a few hours (Bahr et al.