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Determining Basal Energy Expenditure and the Capacity of Thermogenic Adipocytes to Expend Energy in Obese Mice
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Determining Basal Energy Expenditure and the Capacity of Thermogenic Adipocytes to Expend Energy in Obese Mice

Published on: November 11, 2021

Larger mass of high-metabolic-rate organs does not explain higher resting energy expenditure in children

Amy Hsu1, Stanley Heshka, Isaac Janumala

  • 1Institute of Human Nutrition, College of Physicians and Surgeons, Columbia University, New York, NY, USA.

The American Journal of Clinical Nutrition
|June 7, 2003
PubMed

Insights

Children have higher resting energy expenditure (REE) due to larger proportions of metabolically active organs like the brain and liver. This study quantifies these differences to explain REE variations during growth.

Area of Science:

  • Pediatrics
  • Human Physiology
  • Metabolic Research

Background:

  • Children exhibit a high resting energy expenditure (REE) relative to body weight.
  • The decrease in REE during growth is hypothesized to stem from shifts in body composition or organ-specific metabolic rates.

Purpose of the Study:

  • To quantitatively assess body composition at the organ-tissue level in children in vivo.
  • To determine if these organ-tissue masses explain the elevated REE in children.
  • To ascertain if organ-tissue metabolic constants, combined with mass, account for children's REE.

Main Methods:

  • Cross-sectional study of 15 children (9.3 ± 1.7 years) and 13 adults (26.0 ± 1.8 years) with BMI < 30.
  • Magnetic resonance imaging (MRI) used to measure in vivo masses of brain, liver, kidney, heart, skeletal muscle, and adipose tissue.
  • Resting energy expenditure (REE) measured via indirect calorimetry (REE(m)) and calculated (REE(c)) using established metabolic coefficients.

Main Results:

  • Children showed a significantly greater proportion of liver (3.7% vs 3.1%) and brain (6.2% vs 3.3%) mass relative to adipose-tissue-free mass compared to adults.
  • While brain and liver mass improved predictive models, age remained a significant factor.
  • Calculated REE (REE(c)) significantly underestimated measured REE (REE(m)) in children (3869 ± 615 kJ/d vs 5119 ± 769 kJ/d).

Conclusions:

  • The decline in REE during growth is likely attributed to both a reduction in the relative mass of highly metabolic organs and tissues.
  • Changes in the intrinsic metabolic rates of individual organs and tissues also contribute to the observed REE decline.
Abstract

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