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.