There are five methods that are commonly used in national surveys to assess food insecurity . Of these, four are indirect or derivative measures of food insecurity (FAO method, household expenditure surveys, dietary intake assessment and anthropometry). All the methods complement each other and none should be considered superior over another one. In most instances, the method of choice depends on the question that needs to be answered, as well as the budget available to conduct the assessment. Ideally, food security assessments should be based on the application of several of these methods. This way, different dimensions from the food insecurity problem can be addressed in the same survey or study.

The only method that represents a fundamental or direct measure of food insecurity is the one based on experience-based food insecurity measurement scales. Whereas the FAO method concentrates on food insecurity risk at the national level, the remaining methods discussed concentrate on assessing the risk at the individual or household level. Likewise, whereas some of the derivative measures assess the determinants (i.e., dietary intake, food expenditures), others measure the consequences of food insecurity (i.e., anthropometry). Thus, as indicated above, all the methods complement each other and the method of choice depends on the question being answered and the economic and logistical resources available to collect valid data. All the methods have serious measurement error issues that can be attenuated by fully understanding the principles underlying them and the use of highly trained and standardized research field workers.

Nutrition security is a process that can be understood at the organism level as it is achieved when the cells and the tissues and organs that form the human body are properly nourished. Nutrition security is the product of food security and health security and the interrelationship between the two. Thus, nutrition security is derived from access to both a healthy diet and to preventive and curative healthcare. Both food security and health are strongly linked with available household income. Another factor that influences food security is the availability of a variety of nutritious foods at the local, regional, and national level. The availability of foods at the national level depends on local production for local consumption, as well as on the ability to import a variety of healthy and nutritious foods. Thus, a stable and sustainable global food supply is essential for ensuring food security. In sum, household food security and the individual's nutrition security depend on local, regional, national, and global factors. The following section presents the most commonly used food insecurity assessment methods. These methods were identified by: a) reviewing United Nations agencies documents as these agencies are most involved compiling food insecurity assessments worldwide, and b) reviewing food insecurity assessment documents published during the last decade.

Methods for measuring food security

There are five commonly used methods that can be used to assess food security3 : i) the Food and Agriculture Organization (FAO) method for estimating calories available per capita at the national level; ii) household income and expenditure surveys; iii) individual's dietary intake; iv) anthropometry; and v) experience-based food insecurity measurement scales.

The FAO method

This method estimates calories per capita at the country level using Food Balance Sheets and energy intake variance data derived from household income and expenditure surveys. Countries need the following information to be able to apply this method: i) total calories available in year of interest; ii) number of people living in country in year of interest; iii) coefficient of variation of caloric intake to generate the energy intake distribution curve; iv) cut-off point to estimate the proportion of the population falling under the minimum per capita average caloric requirement.

Advantages

The main advantages of this method are that: i) almost all countries generate the data needed and estimate their daily per capita caloric availability; ii) estimates are frequently updated thus allowing the national, regional,