Graphic visualization of the relations of metabolic fuels:heat:O₂:CO₂:H₂O:urine N

¹ Department of Biophysics, University of Western Ontario, London, Canada; and Department of Physiology, University of Buffalo School of Medicine, Buffalo, New York

The quantitative relations among the various measured and calculated variables of metabolism can be described much more clearly by graphs than in words or tables. A system of graphing is presented whereby these relations can be shown on any of 105 different graphs in terms of straight lines. The metabolic variables treated are: carbohydrate, fat, protein (or urinary nitrogen), heat, O₂, CO₂ and metabolic water. Since the values of any three of these are sufficient to define the metabolic situation, they define on the graph a point which stands for that situation, and from which the relative values of all the other variables can be read off. Theoretical principles of the system are given whereby the general layout of any of the 105 graphs can be easily found. The graph on axes of O₂/heat vs. CO₂/heat is selected for development and is used to show the relations of the metabolic variables, not only for the case of simple catabolism of fuel mixtures, but also for cases involving fuel syntheses, ketosis, lactic acid production, and measurement errors due to unsteady states.