Body composition of a nine-year-old reference boy.

Utilizing available data and several assumptions, the body content of water, minerals, protein, carbohydrate, and fat has been estimated for a 9-year-old reference boy. This reference boy is leaner than the reference man (13.4 versus 15.3% of body weight) and his fat-free body mass exhibits greater concentration of water (75.5 versus 73.7%) and lesser concentrations of potassium (66.8 versus 68.1 mEq/kg) and total minerals (4.7 versus 6.9%). If age-specific values are used for composition of fat-free body mass body composition), it will be possible to avoid underestimation of fat content calculated from data on total body water and overestimation of fat content calculated from 40K counting data or from body density determined by underwater weighing.