Energy expenditure differs by race, sex, and weight among Louisiana school children

The identification and treatment of overweight before the onset of adolescence has important implications for health later in life, because overweight during adolescence is an independent risk factor for adult obesity and the adverse health effects that accompany it. In a new study in the American Journal of Clinical Nutrition, DeLany et al. studied 131 preadolescent children and found that the children's energy expenditures varied by their race, sex, and weight and that each of these factors have an influence on whether a child is or will become overweight.

The children averaged 10 to 11 years in age, and were part of the Baton Rouge Children's Study in Louisiana. The sexes and races of the subjects were evenly distributed. Body composition, energy intake (calories), and energy expenditure were assessed in a portable laboratory that was driven to the children's school each day. A calculation of total daily energy expenditure was derived from each child's resting metabolic rate (RMR), the thermic effect of digesting food, and the energy expended in physical activity (AEE). Children were considered lean if they had <25% body fat and obese if they had 25% body fat.

As a group, the boys had a greater total energy expenditure than the girls, although most of this difference could be accounted for by a 25% lower AEE among the African American girls. The only significant difference in body composition between the races was a higher fat-free mass in African American children than in white children. In general, African American children expended less energy than white children. RMR was lower in the African American children; however, the difference in RMR due to race was smaller in girls than in boys. African American boys tended to have the same activity levels as white boys, whereas the white girls tended to have a higher AEE than did the African American girls.

Metabolic rates and energy expenditures also differed between obese and lean children. Obese children had a higher RMR and a lower AEE than did lean children, with the lower AEE more apparent in boys than in girls. The obese children's higher metabolic rate might be explained by their greater fat mass, since both fat and lean tissue are metabolically active. Despite the fact that the obese children had a higher RMR, they may maintain their obese state by spending less time in physical activity. The study's findings emphasize the importance of increasing daily physical activity for overweight or obese children, regardless of their race or sex.

DeLany, James P, et al. Energy expenditure in predolescent African American and white boys and girls: the Baton Rouge Children's Study. Am J Clin Nutr 2002;75:705-13.

This media release is provided by The American Society for Clinical Nutrition to provide current information on nutrition-related research. This information should not be construed as medical advice. If you have a medical concern, consult your doctor. To see the complete text of this article, please go to:

http://www.faseb.org/ajcn/April/11952-DeLany.pdf

For more information, please contact: delanyjp@pbrc.edu

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