Food insecurity occurs when a household or individual does not have predictable access to food in sufficient quantity and quality to maintain an active and healthy lifestyle. The third pillar, the use of food, basically translates the food available to a household into nutritional security for its members. The definition of food security is often applied to different levels of aggregation, even though it is articulated at the individual level. It also suggests that questionnaire-based methods of food insecurity (or even observations of food intake) routinely underestimate the utilization component of food insecurity and this is biased, so that less hygienic environments tend to show a greater mismatch between subjective measures or measures of food insecurity based on experience and measures of malnutrition.
At least among children, there is other evidence that the quality and quantity of diet (and diseases), standard measures of food insecurity, are not necessarily responsible for the high prevalence of stunted growth and underweight seen in many low-income, high-mortality countries. Progress continues in the fight against hunger, but an unacceptably large number of people lack the food they need to lead active and healthy lives. Basic food crops are the main source of dietary energy in the human diet and include products such as rice, wheat, sweet potatoes, corn and cassava. Food security analyzed at the household level is conditioned by the household's own food production and by the ability of household members to purchase food of the appropriate quality and diversity in the market.
A person must have access to enough foods of the right dietary combination (quality) at all times to be food safe. Of course, if stunting was directly equated with hunger or lack of food, food waste would not be expected. Improvements in agricultural productivity are necessary to increase rural household incomes and access to available food, but they are insufficient to ensure food security. The world produces more than enough food, but an unknown (but probably quite large) number of people cannot reliably access these foods.
When analyzing food security at the national level, it is important to understand not only domestic production, but also the country's access to food on the world market, its foreign exchange earnings and the choices of citizens as consumers. Access to food is fundamental and, for this reason, much research has focused on measuring the access component of food insecurity. Finally, and strangely enough, data from at least two studies that actually measured the amount of food that children did not eat (but were offered) reveal that children with stunted growth ate only about 70% of what was offered to them.