A two-reservoir energy model of the human body.

A macroscopic two-reservoir model relating body weight, exercise, basal metabolism, and food intake is developed from the principle of the conservation of energy. A feature of this model is that it can account for changes in aqueous fluids. Experimental data on subjects undergoing a semistarvation diet are fit by the adjustment of a single parameter. The effects of changes in the activity level on the equilibrium body weight and the variation of the equilibrium body weight in individuals of different food utilization efficiencies are considered. The hypothesis that over-eating may lead initially to a volume displacement of aqueous fluids by fat is demonstrated by application of the model to experimental data; this hypothesis obviates paradoxical results suggested by single reservoir concepts.