Developmental changes in energy expenditure and physical activity in children: evidence for a decline in physical activity in girls before puberty.
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.
Goran
M I
MI
Division 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.
Gower
B A
BA
Nagy
T R
TR
Johnson
R K
RK
D001481:Basal Metabolism; D002648:Child; D002657:Child Development / Q000502:physiology*; D002675:Child, Preschool; D002149:Energy Intake; D004734:Energy Metabolism; D015444:Exercise; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D005082:Physical Exertion; D011627:Puberty; D012737:Sex Factors