Resting Energy Expenditure per Lean Body Mass Determined by Indirect Calorimetry and Bioelectrical Impedance Analysis in Cats

Background: Resting energy expenditure (REE) approximates >= 60% of daily energy expenditure (DEE). Accurate REE determination could facilitate sequential comparisons among patients and diseases if normalized against lean body mass (LBM). Objective: (1) Validate open-flow indirect calorimetry (IC) system and multifrequency bioelectrical impedance analysis (MF-BIA) to determine REE and LBM, respectively, in healthy nonsedated cats of varied body conditions; (2) normalize REE against LBM. Animals: Fifty-seven adult neutered domestic short-haired cats with stable BW. Methods: Continuous (45-min) IC-measurements determined least observed metabolism REE. Cage gas flow regulated with mass flow controllers was verified using nitrogen dilution; span gases calibrated gas measurements. Respiratory quotient accuracy was verified using alcohol combustion. IC-REE was compared to DEE, determined using doubly labeled water. MF-BIA LBM was validated against criterion references (deuterium, sodium bromide). Intra-and interassay variation was determined for IC and MF-BIA. Results: Mean IC-REE (175 +/- 38.7 kcal; 1.5-14% intra-and interassay CV%) represented 61 +/- 14.3% of DEE. Best MF-BIA measurements were collected in sternal recumbency and with electrodes in neck-tail configuration. MF-BIA LBM was not significantly different from criterion references and generated LBM interassay CV% of 6.6-10.1%. Over-and underconditioned cats had significantly (P <= .05) lower and higher IC-REE (kcal/kg) respectively, compared with normalconditioned cats. However, differences resolved with REE/LBM (approximating 53 +/- 10.3 kcal/LBM [ kg]). Conclusions and Clinical Importance: IC and MF-BIA validated herein reasonably estimate REE and LBM in cats. REE/ LBM(kg) may permit comparison of energy utilization in sequential studies or among different cats.