A note on methodology - how the numbers are calculated
Chronic food insecurity is represented by estimates of the number of people whose food intake does not provide enough calories to meet their basic energy requirements - i.e. the undernourished. Measurements of nutritional status or undernutrition, on the other hand, are based on information about people's actual physiological condition.
In practice, these are two distinct and useful measures derived from very different analytical approaches.
1. Undernourishment is estimated from existing data about numbers of people and the amount of food available to them.
2. Undernutrition is determined from data about people's weight, height and age. Ratios calculated from these measurements indicate the outcome not only of inadequate food intake but also of poor health and sanitation conditions that may prevent people from deriving full nutritional benefit from what they eat.
The two approaches are complementary, as illustrated:
The numbers cited in this section refer to estimates of undernourishment based on a few commonly available types of information:
The method is described in detail in The Sixth World Food Survey, published by FAO in 1996. Very briefly it relies on:
1. calculating the total number of calories available from local food production, trade and stocks;
2. calculating an average minimum calories requirement for the total population based on the number of calories needed by different age and gender groups and the proportion of the population each group represents;
3. dividing the total number of calories available by the number of people in the country;
4. factoring in a coefficient for distribution to take account of inequality in access to food;
5. combining this information to construct the distribution of the food supply within the country. This gives the percentage of the population whose food intake falls below the minimum requirement;
6. multiplying this percentage by the size of the population to obtain the number of undernourished people.
These calculations produce an estimate of the number of people in each country whose average calorie intake falls below the minimum required to keep the body going and perform light activity. Adding these numbers together yields a global estimate of the total number of undernourished people.
Measuring nutritional status
Measurements of undernourishment are based on estimates of food intake. But to measure malnutrition it is necessary to use anthropometric indicators that tell what is happening to people's bodies.
Estimates of food intake and anthropometry have different objectives, and each has advantages and limitations. Anthropometric data are currently used primarily to measure the nutritional status of young children. Three different measures of undernutrition are commonly used: wasting, stunting and underweight. Nutritionally deprived children are those who are significantly smaller compared to commonly used uniform standards for child growth.
By contrast, in this report prevalence of undernourishment is measured for a total population by comparing food intake data with country-specific food need standards. These are determined on the basis of energy requirements of each sex-age group, taking into account sex- age specific heights within the population.
Anthropometric data are obtained through surveys whose frequency and timing vary from country to country. As a result, these data must be used cautiously in making comparisons between countries and time periods. Food intake measurements, on the other hand, rely on data that are more readily available, recent and fully comparable across countries. So they can be used effectively to obtain a snapshot of current conditions, even though they do not capture the full array of factors determining nutritional status.