Assessment of body fatness in childhood obesity: evaluation of laboratory and anthropometric techniques.

The identification of obesity as a pathological diagnosis depends on an accurate assessment of body fatness and a correlation of fatness with pathological consequences. Because total body fat varies with body weight, the proportion of body weight that is fat is probably a more reliable indicator of risk. Among obese children and adolescents, several problems have hindered the development of accurate clinical measures of percent body fat and total body fat. First, the use of direct methods to measure body composition is limited by expense and labor. Second, the relationship between anthropometric indexes and body composition in obese children and adolescents has not been intensively studied. Third, sample sizes of normal weight children have been too small to permit the development of diagnostic criteria. Fourth, the triceps skinfold is less reproducible in overweight subjects. Increases in lean body mass in obese adolescents may confound the use of the body mass index as a measure of adiposity. Current laboratory methods for the measurement of body composition include: (1) underwater weighing, (2) 40K counting, (3) isotopic dilution measures, (4) neutron activation, and (5) electrical impedance. This article examines relationships between those methods and anthropometry in the measurement of fatness in children and adolescents, as well as the difficulties in measuring body fatness and the importance of body fat distribution and its relationship to morbidity in children. Current evidence suggests an association of morbidity and upper segment obesity in adults. Corresponding studies in children and adolescents are yet to be carried out.