High ratio of resting energy expenditure to body mass in childhood and adolescence: A mechanistic model

Background: Children have lower resting energy expenditure (REE) but higher ratio of resting energy expenditure to body mass (REE/BM) than do adults. This well‐known observation has never been quantitatively explained.Objectives: The aim of the present study is to understand the high REE/BM in childhood and adolescence.Design: A mechanistic REE/BM model is proposed. Literature data on REE, BM and the masses of four high metabolic rate organs (i.e., liver, brain, heart and kidneys) of 1–18 y boys and girls were used to evaluate the proposed REE/BM model. Specifically, we tested the hypothesis that the magnitude and variation of the REE/BM can be predicted by a combination of four variables, including relative cellularity, growth energy expenditure for constructing new cells, fraction of body mass as individual organs/tissues, and their specific resting energy expenditure.Results: The REE/BM provided by the literature is 54 kcal/kg per day at 1 year, decreasing to 26.0 kcal/kg per day at 18 years. Model‐predicted REE/BM can account for 97.0% and 100.7% of the literature‐reported REE/BM in males and females, respectively. The average differences between literature‐reported and model‐predicted REE/BM are 1.1 kcal/kg per day in boys and −0.3 kcal/kg per day in girls.Conclusion : The high REE/BM ratio in childhood results from two model variables: the high fraction of body mass as liver, brain, heart, and kidneys, and their high specific resting metabolic rates. The proposed REE/BM model promotes understanding of the REE, and allows a rational establishment of energy requirements for children and adolescents. Am. J. Hum. Biol., 2012. © 2012 Wiley Periodicals, Inc.