A Comparison of Three Prediction Equations for Estimating Energy Requirements

Abstract

LEARNING OUTCOME: To determine the accuracy of three methods of predicting energy requirements across a range of energy needs. The accurate prediction of energy requirements is a challenge facing many dietitians. We have previously developed a regression equation using fat-free mass(FFM) to predict 24-hour(hr) energy expenditure(EE) based on whole-room indirect calorimetry. This equation was developed from calorimetry data where subjects were not performing any prescribed physical activity. Thirty female and 34 male subjects, aged 30.7 (+/−7.1) years, had measurements of body composition by hydrodensitometry, resting metabolic rate(RMR) using a ventilated hood system and 24-hr EE determined during a stay in a whole-room indirect calorimeter. During the stay in the calorimeter, subjects performed a low-intensity stepping and walking exercise to simulate usual sedentary daily activity. Subjects were primarily Caucasian (95% of sample) and all were weight-stable with a mean body mass index(BMI) of 23.4 +/−3.0 kg/m 2. Measured 24-hr EE was compared to three methods of prediction: 1) the regression equation based on FFM, 2) RMR and 3) the Harris-Benedict equation. An activity factor of 1.3 was applied to each method. The group mean difference (<200 kcals) between measured and predicted energy requirements were not significantly different among the three estimation methods. All methods predicted energy requirements similarly across a wide range of estimated energy needs. It is important to note that a larger error was associated with predicting energy requirements in those individuals whose measured 24-hr EE was greater than 2500 calories regardless of the method used. A possible reason for this variance may be an increased level of spontaneous activity; therefore, an additional factor may be necessary in these equations. In summary, we found that all methods investigated were able to accurately predict energy requirements for a sedentary day in individuals with energy expenditures less than 2500 calories. For a free-living situation, usual physical activity should be assessed so that an appropriate activity factor can be used. Dietitians should be also be aware that these equations may need to be modified for individuals with high energy needs.