Hypocaloric Parenteral Nutrition in Obese Patients: A Comparison of Measured Resting Energy Expenditure and Estimated Energy Expenditure

Measured resting energy expenditure (mREE) was collected in 66 obese (BMI 30.0-39.9 kg/m2), hospitalized patients using indirect calorimetry (CCM Express) at Rush University Medical Center (RUMC) and was compared to estimated resting energy expenditure (REE) using RUMC's hypocaloric guidelines for obese patients receiving parenteral nutrition (10-20 calories/kilogram actual body weight) and other common predictive equations. Pearson's correlation coefficients and Bland-Altman plots were used to assess correlation and agreement, respectively. Accuracy was assessed by the proportion of subjects having predicted energy requirements within ±10% of mREE. No predictive equation was able to consistently demonstrate strong correlation, good agreement, or high accuracy when compared to mREE. Moderately strong correlations were observed for male patients (range of r=0.18-0.69) but not for female patients (r= 0.11-0.39), and only 41% of subjects had estimated energy needs within ±10% of mREE. The Bland-Altman plots demonstrated wide limits of agreement (range of 2000 calories/day) which indicated lack of clinical agreement. Regression analysis was used to create a model that best predicted the range in which energy needs were within +200 to 500 calories of mREE. Results indicated that REE was best estimated when mREE was between 1400-2100 calories/day. Further research should validate results from this range. Guidelines and protocols for feeding the obese at RUMC warrant further investigation.