Food insecurity, as measured in the United States, refers to the social and economic problem of lack of food due to resource or other constraints, not voluntary fasting or dieting, or because of illness, or for other reasons. 
Food Security: Definition & General Information. Food security is defined as the availability of food and one's access to it. A household is considered food secure when its occupants do not live in hunger or fear of starvation. Stages of food insecurity range from food secure situations to full-scale famine. FIGURE 3-1 Core concepts related to nutritional state. Food insecurity, as measured in the United States, refers to the social and economic problem of lack of food due to resource or other constraints, not voluntary fasting or dieting, or because of illness, or for other reasons. This definition, supported by the ethnographic research conducted by Radimer et al. The first and second of these are not the interest of the household food security survey because they refer to a natural phenomenon that all humans experience on a regular basis. The fourth is also not a useful definition or concept of hunger because it refers to the problem of food insecurity itself. This definition is again refined in The State of Food Insecurity 2001: Food security [is] a situation that exists when all people, at all times, have physical, and economic access to sufficient, safe and nutritious food that meets their dietary needs and food preferences for an active and healthy life [31] . 1 Food insecurity—the condition assessed in the food security survey and represented in USDA food security reports—is a household-level economic and social condition of limited or uncertain access to adequate food. 2  Hunger is an individual-level physiological condition that may result from food insecurity.
http://www.disabled-world.com/fitness/nutrition/foodsecurity/ http://www.nap.edu/read/11578/chapter/5 http://www.nap.edu/read/11578/chapter/5 http://www.fao.org/docrep/005/y4671e/y4671e06.htm http://www.ers.usda.gov/topics/food-nutrition-assistance/food-security-in-the-us/definitions-of-food-security.aspx
Which is the best definition of food insecurity?