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Determinants of resting energy expenditure in young children
M I Goran1, M Kaskoun, R Johnson
1Department of Nutrition Sciences, University of Alabama at Birmingham 35294.
Insights
Resting energy expenditure (REE) in children is primarily determined by fat-free mass (FFM) and fat mass (FM), similar to adults. Boys exhibit higher REE than girls, suggesting factors beyond sex hormones contribute to sex-based energy expenditure differences.
Area of Science:
- Pediatric Endocrinology
- Human Physiology
- Nutritional Science
Background:
- Resting energy expenditure (REE) is crucial for metabolic health.
- Adult REE is influenced by fat-free mass (FFM) and fat mass (FM), with men having higher REE than women.
- Limited data exist on the physiological determinants of REE in prepubertal children.
Purpose of the Study:
- To investigate the key determinants of resting energy expenditure (REE) in prepubertal children.
- To compare the factors influencing REE in children with those observed in adults.
- To explore potential influences of ethnicity, parental factors, and obesity on children's REE.
Main Methods:
- Indirect calorimetry was used to measure REE in 113 prepubertal children (ages 3.9-7.8 years).
- Body composition (FFM and FM) was assessed using bioelectrical impedance analysis (Kushner equation).
- Stepwise regression analysis identified significant predictors of REE, including FFM, sex, and FM.
Main Results:
- Fat-free mass (FFM), sex, and fat mass (FM) explained 63% of the variation in REE among children.
- FFM was the strongest predictor (p < 0.001), followed by FM (p = 0.01) and sex (p = 0.001).
- Boys had a higher REE than girls (53 kcal difference), and REE increased with FFM (31.9 kcal/kg) and FM (13 kcal/kg).
Conclusions:
- The primary determinants of REE in prepubertal children are FFM, sex, and FM, mirroring adult findings.
- Higher REE in boys suggests sex-based differences in energy expenditure begin before puberty and may not be solely hormone-driven.
- Obesity in children or parents, ethnicity, and parental factors did not independently predict REE in this cohort.
Abstract:
Resting energy expenditure (REE) in adults is influenced by fat-free mass (FFM) and fat mass (FM), and is significantly higher in men than in women. There are limited data, however, on the physiologic determinants of REE in children. We therefore measured REE in 113 prepubertal children (39 white girls, 41 white boys, 21 Mohawk girls, and 12 Mohawk boys), 3.9 to 7.8 years of age, representing a wide range of body weight (14.7 to 34.0 kg), height (0.97 to 1.30 m), FFM (10.3 to 25.0 kg), and FM (1.7 to 13.7 kg; 9.4% to 40.3%). The REE was measured in duplicate by indirect calorimetry (range, 830 to 1405 kcal/day) while the children were in a postprandial state and viewing a cartoon film. The FM and FFM values were determined by bioelectrical resistance by means of the Kushner equation. In stepwise regression analysis, the combination of FFM (p < 0.001; partial r = 0.77), sex (p = 0.001; partial r = 0.12), and FM (p = 0.01; partial r = 0.16) explained 63% of the variation in REE. The regression coefficients were 31.9 kcal/kg FFM, 53 kcal for boys, 0 for girls, and 13 kcal/kg FM. Mohawk background, age, fat distribution, heart rate, and physical activity were not independently associated with REE. After REE was adjusted for the aforementioned significant factors, there were no significant correlations with parental factors (body composition, physical activity, age, and REE) other than normalized maternal REE (r = 0.19; p = 0.05). We conclude that the effects of FFM, sex, and FM on REE in children are similar to those in adults. The higher REE in young boys suggests that the previously reported higher REE in adult men cannot be explained entirely by differences in sex hormones. Finally, our data do not support the hypothesis that REE in children is negatively influenced by obesity in children or in parents.