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Developmental changes in energy expenditure and physical activity in children: evidence for a decline in physical
M I Goran1, B A Gower, T R Nagy
1Division of Physiology and Metabolism, Department of Nutrition Sciences, and the Obesity Research Center, School of Health Related Professions, University of Alabama at Birmingham, Birmingham, Alabama, USA.
Objective:
To examine individual changes in energy expenditure and physical activity during prepubertal growth in boys and girls.
Methods:
Total energy expenditure (TEE), resting energy expenditure, physical activity-related energy expenditure, reported physical activity, and fat and fat-free mass were measured three times over 5 years in 11 boys (5.3 +/- 0.9 years at baseline) and 11 girls (5.5 +/- 0.9 years at baseline).
Results:
Four-year increases in fat ( approximately 6 kg) and fat-free mass ( approximately 10 kg) and resting energy expenditure ( approximately 200 kcal/day) were similar in boys and girls. In boys, TEE increased at each measurement year, whereas in girls, there was an initial increase from age 5.5 (1365 +/- 330 kcal/day) to age 6.5 (1815 +/- 392 kcal/day); however, by age 9.5, TEE was reduced significantly (1608 +/- 284 kcal/day) with no change in energy intake. The gender difference in TEE changes over time was explained by a 50% reduction in physical activity (kcal/day and hours/week) in girls between the ages of 6.5 and 9.5.
Conclusions:
These data suggest a gender dimorphism in the developmental changes in energy expenditure before adolescence, with a conservation of energy use in girls achieved through a marked reduction in physical activity.