Conicity: A new index of body fat distribution-what does it tell us?

"Conicity" (C) is an index of body fat distribution which expresses an individuals waist circumference relative to the circumference of a cylinder generated with that persons weight and height assuming a constant for body density (Valdez [1991] J. Clin. Epidemiol. 44:955-956). The more central a person is in fat distribution, the higher the value of C. In a pilot study of cardiovascular reactivity and dimensions of anger and hostility in 60 African-, Anglo-, and Hispanic-American adolescents, anthropometry and sexual maturation were determined to assess their mediating influence on the relation between anger and cardiovascular risk. The concurrent validity of three indices of body fat distribution was explored: conicity(C), waist/hip ratio (WHR), and central/peripheral skinfold ratio (C/P) by assessing their association with cardiovascular variables (CV) and other anthropometrics. Anthropometry included height, weight, fat mass estimated from bioelectrical impedance, four circumferences, and skinfolds. Maturation variables included menarche in girls, testes size in boys, and pubic hair in both sexes. Cardiovascular variables included resting diastolic and systolic blood pressures and heart rate, and the same three variables after recovery from a step test. The boys and girls were 15-16 years of age, and there were equal numbers in each sex/ethnic group. Partial correlations accounting for height (which was affected by ethnicity) and maturation stratified by gender are reported. C was more strongly related to CV risk in boys and girls than the other indices or the body mass index. Least related to CV risk was C/P, correlated only weakly to central skinfold fat. C and WHR are highly related (0.85) yet differ in important respects in both sexes: C is more closely related to body fat (0.62-0.66) and fat mass (0.53-0.77) than the WHR (respective correlations: 0.54-0.55 and 0.43-0.66). Thus, C relates not only to body shape but also to body fat. Indices of central fat such as circumference and skinfold ratios, may "over-correct" for total fatness and thus miss important aspects of risk prediction. Conicity may be a useful indicator of body fat distribution in studies of adolescents. © 1996 Wiley-Liss, Inc.