Abstract TAC254: Estimating Resting Metabolic Rate in Youth with Obesity and Elevated Blood Pressure

Background: Achieving and maintaining a healthy weight is one of the AHA’s Life’s Essential 8. Estimating resting metabolic rate (RMR) facilitates weight loss counseling, which is a key aspect to therapeutic lifestyle change in youth with hypertension. RMR equations were established in variable populations; it is unknown how these equations perform in youth with significant obesity. Objective: Determine the agreement between measured and predicted RMR among youth with obesity and elevated blood pressure (BP). Methods: Pediatric patients with obesity and elevated BP who were referred for hypertension evaluation underwent indirect calorimetry using a Vmax Encore metabolic cart after fasting, abstaining from nicotine use x4 hrs, and avoiding vigorous physical activity x12 hrs. Paired t-tests compared measured to estimated RMR obtained using predictive equations (kcal/day; Table 1). Comparisons were made for the population overall and stratified by sex and race. Bland-Altman plots illustrated the overall mean difference and the limits of agreement (LOA). Results: Thirty-one youth, 6-20 yrs of age [mean 14 yrs, standard deviation (SD) 3.3] participated: 35% female (n=11), 68% (n=21) Black, mean weight 114.9 kg (SD 35.9), and mean BMI 41.31 kg/m2 (SD 9.9). Measured and estimated RMR are displayed in Table 2. There was no bias detected and there were minimal/no outliers (Figure). The Harris-Benedict, a commonly used equation in clinical practice which was developed in Caucasian individuals of normal weight, had an overall mean difference of +176 kcal/day when compared to measured RMR and had a slightly greater overestimation among male and Black youth (~200 kcal/day). The Mifflin St. Jeor, developed in a population whose racial composition was not specified but had a large proportion of individuals with obesity (47%), best estimated RMR for all participants with an overall mean difference of -24 kcal/day and nearly identical estimated-to-measured RMR in each subgroup of sex and race. Conclusion: In this study of majority Black youth 6-20 yrs of age with obesity, we found significant differences between the predicted and measured RMR. The Mifflin-St. Jeor predictive equation provided the best estimate of RMR, highlighting the importance of diversified patient populations when developing predictive equations for use in the general pediatric population.