Comparison of several equations and derivation of a new equation for calculating basal metabolic rate in obese children

Objectives: To compare basal metabolic rate (BMR) calculated by the Harris-Benedict, Ravussin, Cunningham, World Health Organization (WHO) and Schofield equations to BMR determined in an obese pediatric population. The second objective is to derive a new equation, based on measured BMR in obese children, for calculating BMR in obese pediatric patients. Methods: The study included 110(50 male/60 female) healthy obese subjects (BMI>28) (11.7 +/- 2.8 years, 73 +/- 27 kg, 152 +/- 14 cm and 38 +/- 6% fat) who had preprandial BMR determined by indirect calorimetry. These results were compared to BMR calculated with the five above mentioned equations. Fat-free mass was determined by bioelectrical impedance and body composition was calculated using the appropriate equation. The age groups analyzed were as follows: males 3 to 10 and 11 to 18 years old; females 3 to 10 and 11 to 18 years old. A new equation was derived by stepwise multiple regression analysis using 100 randomly selected subjects from our test group and tested using the remaining 10 subjects. Results: Basal metabolic rate calculated by the Ravussin and Cunningham equations in all subgroups was lower (p<0.05) than measured BMR. Basal metabolic rate calculated by the Harris-Benedict equation was lower (p<0.05) than measured BMR in male populations ages 3 to 10, 11 to 18, and in the entire cohort. Measured BMR was overestimated by the Harris-Benedict equation (p<0.05) in females 11 to 18 years old; by the WHO equation (p<0.05) in both male and females 3 to 10 years old and by the Schofield equation (p<0.05) in males 11 to 18 years old. In comparison to measured BMR, the WHO equation appeared to be the most accurate for estimating BMR in males and females 11 to 18 years old. However, BMR calculated using our new equation in the 10 test subjects was similar to measured BMR. Conclusions: The WHO equation was the most accurate of the prediction equations studied. However, our new prediction equation may be more appropriate for calculating BMR in an obese pediatric population.