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What is undernourishment and how is it measured?

‘Undernourishment’ is the main indicator used by the Food and Agriculture Organization of the United Nations to measure the extent of food supplies and nutrition. It is often used interchangeably with the term ‘hunger’.

Undernourishment is solely determined by the sufficiency of energy (calorie) intake. It does not consider the quality or diversity of someone’s diet. That means it is only one component of malnutrition: a broader term that also captures other types of nutrient deficiencies, such as micronutrients. 

The prevalence of undernourishment in any given country or region measures the share of the population that has a daily food intake that is insufficient to provide, on average, the amount of dietary energy required to maintain a normal, active and healthy life. That is, the share of people who do not get enough calories to live a healthy life.

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How is undernourishment measured?

To judge whether someone was undernourished we would need to know two things:

  1. How many calories they consume;
  2. How many calories they need to maintain a healthy life.

This might be easy for a known individual, but measuring this across a whole population is more difficult. 

The amount of calories that people need can be very different: factors such as someone’s height, weight, sex, age, and activity levels will mean that some people need more calories than others.

The amount of calories that people consume also varies widely – some people eat more than their requirements – which can lead to obesity – while others eat well below their requirements.

This means we cannot simply calculate undernourishment from an average of calorie consumption and requirements.

To take account of this, the UN FAO address inequalities in these two factors in the following ways1:

  1. They measure the levels of inequalities in food consumption within a population. This is called the Coefficient of Variation (CV) of energy intake. This metric is shown in the map. As we see, this value varies from country to country depending on the inequalities in food supply.
  2. They use demographic information – such as the age structure, sex, height and activity levels – for each country to assess the distribution of energy requirements. This means the ‘minimum energy requirement’ for each country is slightly different, as shown on the map.

Using these two distributions – of the variation in intake and energy requirements, they then calculate undernourishment using a ‘parametric probability density function’. This indicates the cumulative probability across a population that someone has a daily energy intake that is lower than the minimum requirements.

This undernourishment measure, therefore, does not tell us anything about what specific individuals are undernourished. But it gives us an estimate of what share of a population do not get enough calories to eat.

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