The objective of this core are to provide members of the Center with the following: 1. Consultative services regarding the most appropriate uses and limitations of various approaches to the measurement of body composition in normal human subjects or those with obesity, undernutrition, or conditions that predispose to malnutrition. 2. Reliable measures of body compositions using total body potassium, total and partial body neutron inelastic scattering, bioelectric impedance, anthropometry, and dual photon absorptiometry (DXA). 4. Training for young investigators in methods to measure body composition. 5. Extension of selected methods used in human studies to animal models of obesity. 6. Validation of universally available body composition against neutron inelastic scattering.