This volume provides a comprehensive survey of the theory, practice, and techniques of calorimetry as applied to the study of energy metabolism in humans and animals. Calorimetry is used to estimate nutritional requirements of man and farm livestock and to evaluate different foods. It is also a powerful tool used in research into fundamental nutritional and physiological life processes and in the evaluation of stresses imposed by abnormal or severe environments. It is currently being applied in various branches of medical research and can be used as a diagnostic tool in hospitals for investigation of metabolic disorders. The authors discuss both direct calorimetry, which measures heat loss directly, and indirect calorimetry, where heat loss is inferred by measurement of some of the chemical byproducts of metabolism. In addition, guidance is provided to the instrumentation, technical problems, and precautions necessary to obtain accurate calorimetric measurements.