Stunting, Wasting, and Underweight

Stunting, wasting, and underweight are the three principal anthropometric forms of child undernutrition. They are defined by comparing a child's measurements against growth standards: low height-for-age (stunting), low weight-for-height (wasting), and low weight-for-age (underweight). This topic covers how they are defined and measured, what they signify, and their global burden.

Definition

Stunting is low height (length) for age, indicating chronic or recurrent undernutrition; wasting is low weight for height, indicating recent or severe weight loss (acute undernutrition); and underweight is low weight for age, a composite reflecting both. Each is conventionally defined as a measurement more than two standard deviations below the median of a reference growth standard.

Scope

The entry treats these indicators as public health measures of child nutritional status: their definitions relative to the WHO Child Growth Standards, what each reflects about chronic versus acute deprivation, and the population epidemiology and consequences of undernutrition. It is descriptive and reference-oriented and is not a guide to diagnosing or managing an individual child.

Core questions

• How are stunting, wasting, and underweight defined and distinguished?
• What does each indicator reveal about chronic versus acute undernutrition?
• How large is the global burden of child undernutrition and where is it concentrated?
• What are the long-term consequences of early-life undernutrition?

Key concepts

• Height-for-age (stunting)
• Weight-for-height (wasting)
• Weight-for-age (underweight)
• Z-scores and the -2 SD threshold
• WHO Child Growth Standards
• Chronic versus acute undernutrition
• Severe acute malnutrition

Mechanisms

The three indicators capture different time courses of nutritional deprivation. Wasting reflects rapid weight loss from acute food deficit or illness and can change quickly; stunting reflects the cumulative effect of inadequate nutrition and repeated infection over the first 1000 days and is largely irreversible after early childhood; underweight, as weight-for-age, combines elements of both. Standardised z-scores against the WHO growth standards make these states comparable across populations, with values below minus two standard deviations marking moderate and below minus three marking severe forms (WHO MGRS Group, 2006; de Onis & Branca, 2016).

Clinical relevance

These anthropometric categories are the standard indicators by which child undernutrition is described, monitored, and targeted in public health and clinical settings, and severe forms are associated with substantially higher mortality. The topic explains the indicators and their population significance for reference and education; assessment and management of an individual child are clinical matters beyond the scope of this entry.

Epidemiology

Child undernutrition remains a major global problem: stunting affects a large share of children under five, concentrated in South Asia and sub-Saharan Africa, while wasting, though less prevalent at any moment, carries a high risk of death and clusters in food crises; underweight overlaps with both. Undernutrition is a leading underlying contributor to deaths in children under five (Black et al., 2013; de Onis & Branca, 2016).

Evidence & guidelines

The indicators rest on the WHO Child Growth Standards, which provide an international reference for assessing growth (WHO MGRS Group, 2006). Global burden and consequences are synthesised in the Lancet maternal and child nutrition series (Black et al., 2013; Victora et al., 2008), and stunting specifically is reviewed by de Onis and Branca (2016).

History

Anthropometric classification of undernutrition was systematised through twentieth-century work, but the modern definitions rely on the WHO Child Growth Standards released in 2006, which were derived from healthy children across diverse settings and replaced earlier growth references. Long-term follow-up studies and the Lancet series then clarified that early stunting predicts later human-capital deficits (WHO MGRS Group, 2006; Victora et al., 2008).

Debates

Are stunting and wasting separate or overlapping conditions?

Once treated as distinct, growing evidence shows stunting and wasting frequently co-occur in the same children and share risk factors, prompting debate over more integrated measurement and programming.

Key figures

• Mercedes de Onis
• Cesar G. Victora
• Reynaldo Martorell
• Francesco Branca

Seminal works

• black-2013
• victora-2008
• de-onis-2016

Frequently asked questions

What is the difference between stunting and wasting?

Stunting (low height-for-age) reflects chronic, long-term undernutrition, whereas wasting (low weight-for-height) reflects recent, acute weight loss; this entry describes the indicators rather than directing care for any child.

Why is the WHO Child Growth Standards reference used?

It provides a single international standard, derived from healthy children in varied settings, against which a child's measurements are converted to z-scores so that undernutrition can be defined and compared consistently across populations.