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Published on: November 11, 2021
An evaluation of resting energy expenditure in hospitalized, severely underweight patients
A Ahmad1, D R Duerksen, S Munroe
1Department of Medicine, Beth Israel Deaconess Medical Center, Boston, Massachusetts 02215, USA.
Insights
Estimating resting energy expenditure (REE) for severely underweight patients using standard formulas like Harris-Benedict significantly underestimates their actual energy needs. A weight-based empirical formula is recommended for better accuracy in this population.
Area of Science:
- Clinical Nutrition
- Metabolic Research
- Medical Statistics
Background:
- Severely underweight hospitalized patients present unique metabolic challenges.
- Accurate estimation of resting energy expenditure (REE) is crucial for nutritional management in this vulnerable group.
- Existing predictive formulas may not adequately represent the energy requirements of patients below 50 kg.
Purpose of the Study:
- To compare measured REE with estimates from the Harris-Benedict formula and a simple empirical formula in severely underweight patients.
- To evaluate the accuracy of common REE estimation methods in this specific patient population.
- To identify a more reliable method for determining energy needs in severely underweight individuals.
Main Methods:
- A prospective trial involving 14 severely underweight hospitalized patients (mean weight 40.9 kg).
- Measurement of REE using indirect calorimetry (Sensormedics Deltatrac MBM100).
- Estimation of REE using the Harris-Benedict equation and an empirical formula (25 kcal/kg).
Main Results:
- Both the Harris-Benedict and empirical formulas significantly underestimated measured REE (MREE) in all patients (P<0.0001).
- Percentage differences were 18.4% for Harris-Benedict and 20.9% for the empirical formula.
- Body weight showed a better correlation with MREE (r²=0.558) than the Harris-Benedict formula (r²=0.275), indicating weight as a primary determinant.
Conclusions:
- Standard formulas like Harris-Benedict routinely underestimate energy needs in severely underweight patients (<50 kg).
- The Harris-Benedict equation has limited predictive value for individual energy expenditure in this group.
- An empirical equation using 30-32 kcal/kg is suggested for estimating energy requirements when direct measurement is not feasible.
Abstract:
A prospective trial was conducted with 14 hospitalized patients who were severely underweight with a mean weight of 40.9+/-5.1 kg and 70.7+/-7.8% of ideal body weight, to compare estimates of resting energy expenditure (REE) with measured values. The 9 women and 3 men, whose mean age was 66.5+/-13.9 y, underwent nutritional assessment and measurement of their REE by indirect calorimetry using the Sensormedics Deltatrac MBM100 indirect calorimeter. Their REE was also estimated by the Harris-Benedict formula (mean 1032+/-66 kcal/d) as well as a previously established empirical formula where REE = 25 x body weight in kg (mean 1023+/-129 kcal/d). Results by both estimates were significantly lower than the measured resting energy expenditure (MREE) in this group of patients (P<0.0001). The percentage difference between MREE and estimated REE by the Harris-Benedict formula was 18.4+/-9.4% and 20.9+/-7.5% by the empirical formula. The MREE exceeded the estimated REE in each individual. The correlation between MREE and body weight (r2 = 0.558, r = 0.005) was better than that between MREE and estimated REE by Harris-Benedict formula (r2 = 0.275, P = 0.08) suggesting that weight was the principal determinant rather than the other components (height, age, sex) of the Harris-Benedict formula. Our data shows that commonly employed formulae routinely underestimate the energy needs of severely underweight patients below 50 kg in body weight. The Harris-Benedict equation had limited predictive value for the individual, explaining approximately 25% of the variance in energy expenditure. Given the particular importance of matching energy intake to needs in this group of patients with limited reserves, many of whom are critically ill, we suggest an empirical equation using 30-32 kcal/kg be used to estimate the energy requirements of severely underweight patients when direct measurements are unavailable or clinically less imperative.
