Fraction of carbon-free body mass as oxygen is a constant body composition ratio in men

Although elements are the foundation of the human body, information concerning the atomic level of body composition is still limited. The aim of this study was to explore potentially constant relationships among elements found in vivo. Based on the known stoichiometries of relevant chemical components, a theoretical model was derived, suggesting the existence of a relatively constant ratio of total body oxygen to carbon-free body mass (TBO/CFM) in men. Eight elements (C, H, N, Ca, P, K, Na and Cl ) were measured in 22 healthy male subjects by using in vivo neutron activation-40K whole-body counting, and TBO was calculated as the difference between body mass and the sum of the eight measured elements. TBO (in kg) was significantly correlated with CFM (in kg): TBO = 0.829 x CFM - 1.8; r = 0.998, P < 0.001, standard error of estimate = 0.4 kg. The ratio of TBO to CFM was relatively constant, mean +/- SD at 0. 800 +/- 0.009 with a CV of 1.1%. Oxygen and carbon are the two most abundant elements in the human body. The discovery of a constant relationship between oxygen and carbon is not only helpful for understanding the atomic level of body composition, but also provides the possibility of estimating the content of specific elements in vivo.