‘Wasting’ is one of the key indicators used to assess the prevalence of childhood malnutrition. A child is defined as ‘wasted’ if their weight is too low for their height.
Wasting is often referred to as acute malnutrition. It is a sign that a child has experienced short periods of undernutrition, resulting in significant wastage of muscle and fat tissue. This means their weight is very low for their height. Childhood stunting – another important measure of nutrition – is regarded as a stronger indicator of chronic malnutrition.
Wasting can be caused by acute but severe periods of food shortage, or disease, or both. This is often caused by periods of severe food insecurity in a population – such as during famine, or seasons of very poor crop harvest. It can also be the result of bouts of infection, where a child’s energy requirements may be higher and their ability to absorb and retain nutrients is limited.
The prevalence of wasting in a population is measured as the share of children younger than five years old that are defined as ‘wasted’.
Wasting is measured based on a child’s weight relative to their height.
The World Health Organization (WHO) sets out child growth standards – these show the expected trajectory of a child’s growth from birth through to adulthood.1 These include measurements of a child’s expected height and weight. One of the key measures of health is a child’s weight relative to their height. If their weight is too low for their height, it is a sign that they have an insufficient energy intake. Of course, this weight-to-height ratio is not exactly the same for every child. The WHO therefore sets out a range of values around this median expectation. This ‘acceptable range’ spans two standard deviations.
A child whose weight falls two standard deviations below their expected weight for their height is defined as ‘wasted’.
In a population, the prevalence of wasting is defined as the share of child under five years old that fall two standard deviations below the expected weight for their height.
To estimate the prevalence of wasting, researchers draw on household and demographic surveys, which include measurements of childhood growth, alongside official health data from governments that monitor child development.