Journal of the American College of Nutrition, Vol. 17, No. 4, 306-307 (1998)
Published by the American College of Nutrition
Perspectives on Predicting Resting Energy Expenditure in Pediatric Obesity
John J. Cunningham, PhD, FACN
Department of Nutrition
Chenoweth Lab
University of Massachusetts
Amherst, MA
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INTRODUCTION
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A direct measurement of individual resting energy expenditure (REE) is often impractical in the office or clinic setting. A number of years ago I [1] characterized two perspectives from which a prediction of REE could be approached in adults, namely the clinical and the physiologic. The basis for operating within either of these to predict REE is predominantly the availability of accurate measurements for the corresponding variable(s) of interest—weight, height and sex for the clinical perspective or fat-free mass (FFM) for the physiologic perspective. An earlier analysis [2] of the data collected by Harris and Benedict in 1919 [3] showed that these approaches were virtually equal in their utility to estimate REE. The availability, affordability, ease and reliability of bioimpedance analysis for FFM has over time favored a transition to the physiologic approach among practicing clinicians.
As demonstrated by Tverskaya et al in this issue of the Journal [4], neither the clinical nor the physiologic prediction equations for REE that were derived from adult data perform well when applied to pediatric obesity. Their analysis generates a specific prediction equation that confirms the robust relationship between REE and FFM as is generally seen in many studies of adults and children. The relationship between REE and FFM here appears to be characterized by a steeper slope, perhaps indicative of differing components within the FFM during growth relative to the fairly stable FFM in adulthood. Further, in the dynamic pediatric years the importance of an age-specific estimation reveals itself with age as a second significant factor in the physiologic prediction. Age is not contributory to predicting REE from FFM in adults.
In contrast to the Harris-Benedict equations as clinical predictors of REE, the set of pediatric predictions published by the World Health Organization (WHO) [5] do well as clinical predictors in the present study [4]. These WHO equations are age-stratified and sex-specific and can be concluded to be well matched to the FFM by their performance in this analysis. It is consistent with the adult literature to find that FFM or a combination of weight and height within each sex are interchangeable components in deriving the equations for the two perspectives.
One ongoing issue in the interpretation of data sets where REE is measured is a judgment about the importance of the fat mass (FM) as an independent physiologic contributor to REE. Interestingly, in the obese pediatric subjects studied here [4] the relative magnitude and importance of the FM as a component of the physiologic equation is consistent with observations for adults. There appears to be physiologic significance among the obese where FM is disproportionately large, but the contribution is to a far lesser degree than that of FFM (Table 4) in the article by Tverskaya et al.
There are two additional perspectives that operate generally during the development of prediction equations, namely the statistical and the biological perspectives on variable inclusion. Statistical parameters are set to ensure that unbiased and definable criteria drive inclusion decisions while biological interpretations are judgmental assessments about the importance of significant factors. In the present instance, whereas Table 4 shows sex to be a statistically significant inclusion variable during the stepwise regression procedure, I would interpret that it does not in practice improve the biologic prediction to an appreciable degree. That is, when age is included as a factor it increases the explained variation by only 0.01 percent, it reduces the standard error of prediction by only 4 kcals per day, and it is applied only as an "all or nothing" (dummy variable) 82 kcal in the proposed physiologic prediction of REE.
The final and good news message echoed in this study [4] is that the absolute REE is substantially elevated in pediatric obesity, much as it has been shown to be in adults [6]. Therefore, the condition should be readily amenable to intervention strategies that incorporate a reasonable caloric intake coupled with physical activity patterns that can translate into a healthful and lifelong diet/lifestyle plan. A reliable prediction of REE either from bioimpedance and the presently derived prediction (the physiologic perspective) or from the WHO equations (the clinical perspective) provides the starting point for counseling toward a successful resolution of pediatric obesity.
Received April 1, 1998.
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REFERENCES
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- Cunningham JJ: Body composition and metabolic rate: the myth of feminine metabolism. Am J Clin Nut
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- Cunningham JJ: A reanalysis of the factors influencing basal metabolic rate in adults. Am J Clin Nutr
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- Harris J, Benedict G: A biometric study of basal metabolism in man. Washington DC: Cornegue Institution, publ. 279, pp
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- Tverskaya R, Rising R, Brown D, Lifshitz F: Comparison of several equations and derivation of a new equation for calculating basal metabolic rate in obese children. J Am Coll Nutr
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- FAO/WHO/UNU Expert Consultation: "Energy and Protein Requirements." Geneva: World Health Organization,
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- Felig P, Cunningham J, Levitt M, Hendler R, Nadel E. Energy expenditure in the fasting and postprandial state. Am J Physiol
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INTRODUCTION
REFERENCES
