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

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.

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.

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.

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.