Resting Energy Expenditure Measured by Indirect Calorimetry in Obese Patients: Variation Within Different BMI Ranges.

BACKGROUND: The adequate provision of energy for obese patients by estimation without indirect calorimetry (IC) is challenging. The goal was to establish values of kilocalories per kilogram (kcal/kg) for patients in different ranges of body mass index (BMI [kg/m2 ]) comparable to resting energy expenditure (REE [kcal/kg/d]) measurements by IC. METHODS: In 63 overweight (OW) hospitalized patients with BMIs (25.0-29.9) or obesity (OB; ≥30), the REE was measured in fasting and fed states. IC was performed with Deltatrac II on patients with enteral or parenteral nutrition, classified by their BMI, in 3 groups: OW (25-29.9), OB (30-39.9), and morbidly obese (≥40). The actual body weight was measured with a microprocessed bed scale or a precision anthropometric scale, and REE was transformed to kcal/kg. RESULTS: Ninety-seven IC measurements were obtained from 63 patients: in 54 on a ventilator, and of 9 with a canopy; 58 in the fasting state; and 39 after reaching measured caloric requirements. The patients' BMIs ranged from 27.3 to 53.4, average of 33.9 ± 6.2. There were no differences in measured REE (mREE) between the fasting and fed states (P > 0.05) within each BMI group; however, differences were observed when comparing the mREE between the groups in the fed state. CONCLUSION: These results, in kcal/kg/d, suggest using 22.0 for OW, 18.4 for OB, and 16.9 for individuals with BMIs >40. However, we recommend the use of IC to determine REE for the latter subset of patients, since 16.9 kcal/kg/d might be an underestimation.

Assessement of resting energy expenditure of obese patients: comparison of indirect calorimetry with formulae.

BACKGROUND & AIMS: Determining the caloric expenditure of overweight (Body mass index - BMI from 25-29.9 kg/m(2)) or obese (BMI> or =30 kg/m(2)) patients is a difficult task. The importance of the measurement using indirect calorimetry (IC) is to avoid the administration of an inadequate caloric load, which can increase clinical morbidity. The aim of this study was to compare the resting energy expenditure (REE) obtained by IC with that estimated by the Harris-Benedict (HB) and the Ireton-Jones (IJ) equations and a fixed amount of 21 kcal/kg of body weight, using actual, average and adjusted weights. METHODS: A total of 71 IC measurements were prospectively performed in 44 patients using the "DELTATRAC II" calorimeter. In 53 of the measurements the patients were on mechanical ventilation and 18 were performed using the canopy, in the fasting state and 24h after achieving calculated caloric requirements. RESULTS: The best REE prediction value in the fasting state was obtained with the HB equation using the actual body weight (HB/ABW), 1873+/-484 kcal/day (p=0.49) when compared to the REE of 1798+/-495 kcal/day measured by IC. After achieving caloric needs, the best REE prediction values were using the HB/ABW equation, 1873+/-484 kcal/day (p=0.56) and the IJ equation with the adjusted body weight, 2103+/-580 kcal/day (p=0.19) when compared to 1948+/-507 kcal/day measured by IC. Although, when the above results were plotted on the Bland and Altman limits of agreement test their average bias were low, but the ranges of their absolute values from the observed average agreement were large, > or =531 kcal. CONCLUSION: From these data we can conclude that even though the average values obtained with the equations utilized to predict the REE for this population, showed good correlation with those by IC, as they had the best comparative absolute results, however they demonstrated an unacceptable variability when matched to the measured REE values.