The authors of this paper used bibliographic searches, a modified Delphi technique, focus groups, and interviews with experts to identify existing models of agriculture, food, nutrition, health, and environmental systems. They then created an integrated conceptual model of the food and nutrition system based on the results of their data collection. The food and nutrition system consists of the processes necessary to change raw materials into foods and changing nutrients into health outcomes. The conceptual model the authors created is unique because there are very few models which describe the system broadly. This broad model is able to identify links between the different disciplines within the food and nutrition system. The authors explain, "systems theory takes a holistic perspective in examining system boundaries, delineating subsystems and their relationships, emphasizing the process of homeostasis and considering relationships between systems. Systems are viewed as sets of elements that function together as collective units."
Sobal, Jeffery, Laura Kettel Khan, and Carole Bisogni. "A Conceptual Model of the Food and Nutrition System." Social Science & Medicine 47, no. 7 (1998): 853-63.