REPRODUCIBILITY OF 24-H ENERGY-EXPENDITURE, SUBSTRATE UTILIZATION ANDSPONTANEOUS PHYSICAL-ACTIVITY IN OBESITY MEASURED IN A RESPIRATION CHAMBER

OBJECTIVE: Determination of within-subject day-to-day coefficients of variations (CV) of 24-h measurements of spontaneous physical activity (SPA), macronutrient oxidation, energy expenditure (EE) and heart rate (HR). DESIGN: Two 24-h measurements in respiration chamber, separated by 14 days of strict weight stability. SUBJECTS: 22 healthy obese sub jects, 15 females and seven males (age 27-64 y, BMI: 30-39 kg/m(2)). M EASUREMENTS: SPA assessed by microwave radar, substrate oxidation and EE measured by indirect calorimetry and heart rate measured by telemet ry. RESULTS: For 24-h measurements CV was 0.8% for RQ, 6.7% for fat ox idation, 5.6% for carbohydrate oxidation, 14.5% for protein oxidation, and 4.3% for heart rate. SPA assessed by microwave radar was also rep roducible (CV = 9.7%), Within-subject day-to-day coefficients of varia tions (CV) were 1.5 and 1.8% for 24-h EE and sleeping EE, and 4.1% for RMR. Both on day 1 and 14, 93.4% of the variation in 24-h EE could be explained by differences in fat-free mass (92.3 and 92.4%, respective ly) and SPA (1.1 and 1.0%, respectively). Also the algorithm and corre lation between 24-h RQ and 24-h energy balance were highly reproducibl e (r = 0.56, P < 0.01 and r = 0.48, P < 0.05). CONCLUSION: Both macron utrient oxidation, SPA and EE in obese patients can be determined with high reproducibility in a respiration chamber.