Adolescents body composition

Owen GM, Brozek J. 1966. Influence of age, sex, and nutrition on body composition during childhood and adolescence. In FalknerF, ed. Human Development. Philadelphia, PA WB Saunders, 222-238. 

Body composition varies with age. The pediatric population has unique physiologic needs that make nutritional requirements distinctly different than adults. In children, caloric requirements per kilogram are higher because of their higher basal metabolic rate (BMR). BMR is approximately 50-55 kcal/ kg/day in infancy and declines to about 20-25 kcal/kg/day during adolescence. 

To better understand changes in drug disposition, the pediatric population needs to be categorized into various groups (Table 1) because children vary markedly in their absorption, distribution, metabolism, and elimination of medications. This occurs because neonates, infants, children, adolescents, and adults have different body compositions (i.e., as to their percentages of body water and fat) and have their body organs in different stages of development. 

Changes in body composition that occur during development alter the way that drugs are distributed round the body. The most dramatic changes in body composition occur in the first year of life but changes continue throughout development through puberty and adolescence, particularly the proportion of total body fat. 

VanderJagt, D.J., Harmatz, P., Ajovi-Emuakpor, S., Vichinsky, E., and Glew, R.H. (2002) Bioelectrical Impedance Analysis of the Body Composition of American Children and Adolescents with Sickle Cell Disease, J. Pediatr. 140, 681-687. 

Our aim was to re-analyse the relationships between the Heath-Carter somatotype and body composition and to develop prediction formulae for automated bioimpedance-based evaluation of the somatotype in children and adolescents suitable for use in a wide range of age in both sexes. 

The introduction of the simple body was in a sense the final step in the move toward the materialization of chemical composition that we have traced from the early seventeenth century. Though largely unconscious throughout most of the eighteenth century, this move became quite conscious and deliberate with the systematic introduction of the simple body concept in the new nomenclature of the chemical revolution. Metaphysical entities would no longer serve. Chemistry had lost its fumbling adolescence and become a deliberate, self-consciously pursued science. 

No histological changes occurred in the liver of adolescent male rats that were whole-body exposed to 0 or 900 ng/m Aroclor 1242 vapor 23 hours/day for 30 days (Casey et al. 1999). The generation of the vapor-phase test atmosphere was based entirely on the evaporation of a liquid PCB mixture using a system that did not create aerosol droplets, and the concentration and congener composition of the test atmosphere was well characterized. Limitations of this study include only one exposure level and liver end point and a relatively small number of animals (8/group) however, uptake of PCBs in the liver was confirmed by tissue analysis, and the exposure was sufficient to induce effects in other tissues, including the thyroid, which is known to be particularly sensitive to PCBs. 

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