ABSTRACT
Two of the scientific foundations for understanding eating and obesity are the theory of evolution and the physicochemical concept of energy. Animals harness that chemical energy as food, either derived from eating plants directly or indirectly by eating other animals and animal source foods. Absent transportation, the pattern of eating such a food is determined by the frequency with which it is encountered and the amounts at each discrete encounter. Central place foragers also eat from source-to-mouth during parts of the daytime, behavior that we recognize as snacking. Food availability is essential for eating to occur at all, and this availability is dependent on factors including the weather, season of the year, and presence of competitors for the same food sources. In an environment in which food is plentiful and easily available, being an opportunistic eater promotes greatly increased consumption.
