Intra- and interindividual variability of resting energy expenditure in healthy male subjects : biological and methodological variability of resting energy expenditure

The objective of the present study was to investigate the contribution of intra-individual variance of resting energy expenditure (REE) to interindividual variance in REE. REE was measured longitudinally in a sample of twenty-three healthy nen using indirect calorimetry. Over a period of 2 months, two consecutive measurements were done in the whole group. In subgroups of seventeen ind eleven subjects, three and four consecutive measurements were performed over a period of 6 months. Data analysis followed a standard piotocol considering the last 15 min of each measurement period and alternatively an optimised protocol with strict inclusion criteria. Intra-individual variance in REE and body composition measurements (CV intra ) as well as inter-individual variance (CV inter ) were calculated and compared with each other as well as with REE prediction from a population-specific formula. Mean CV intra for measured REE and fat-free mass (FFM) ranged from 5.0 to 5.6% and from 1.3 to 1.6% respectively. CV intra did not change with the number of repealed measurements or the type of protocol (standard v. optimised protocol). CV inter for REE anc REE adjusted for FFM (REE adj ) ranged from 12.1 to 16.1 % and from 10.4 to 13.6 %, respectively. We calculated total error to be 8 %. Variance in body composition (CV intra FFM) explains 19% of the variability in REE ajj , whereas the remaining 81 % is explained by the variability of the metabolic rate (Cv intra REE). We conclude that CV intra of REE measurements was neither influenced by type of protocol for data analysis nor by the number of repeated measurements. About 20 % of the variance in REE adj is explained by variance in body composition.