Prevalence of (moderately or severely) underweight children is the percentage of children under five years old whose weight for age is less than minus two standard deviations from the median for the international reference population ages 0–59 months. The international reference population was formulated by the National Center for Health Statistics as a reference for the United States and later adopted by the World Health Organization (WHO) for international use (often referred to as the NCHS/WHO reference population).
Goal 1. Eradicate extreme poverty and hunger.
Target 2. Halve, between 1990 and 2015, the proportion of people who suffer from hunger.
Child malnutrition, as reflected in body weight, is selected as an indicator for several reasons. Child malnutrition is linked to poverty, low levels of education, and poor access to health services. Malnourishment in children, even moderate, increases their risk of death, inhibits their cognitive development, and affects health status later in life. Sufficient and good quality nutrition is the cornerstone for development, health and survival of current and succeeding generations. Healthy nutrition is particularly important for women during pregnancy and lactation, so that their children set off on sound developmental paths, both physically and mentally. Only when optimal child growth is ensured for the majority of their people will governments be successful in their efforts to accelerate economic development in a sustained way.
The under-five underweight prevalence is an internationally recognized public health indicator for monitoring nutritional status and health in populations. Child malnutrition is also monitored more closely than adult malnutrition.
Method of computation
Data collection and source
At the national level, data are generally available from national household surveys, including Demographic and Health Surveys, Multiple Indicator Cluster Surveys and national nutrition surveys.
For international comparisons and global or regional monitoring, the United Nation’s Children’s Fund (UNICEF) and WHO compile international data series and estimate regional and global figures based on data from national surveys.
World Health Report, annual, World Health Organization, Nutrition Unit (www.who.org).
The State of the World’s Children, annual, United Nations Children’s Fund (www.unicef.org/publications).
Indicators of Sustainable Development: Guidelines and Methodologies, 2001, United Nations Division for Sustainable Development (www.un.org/esa/sustdev/natlinfo/indicators/isd.htm).
World Development Indicators, annual, World Bank (www.worldbank.org/data).
The Growth Chart: A Tool for Use in Infant and Child Health Care, 1986, World Health Organization.
Global Database on Child Growth, World Health Organization (www.who.org).
United Nations Children’s Fund, www.childinfo.org and www.unicef.org.
Periodicity of measurement
Household surveys are generally conducted every three to five years.
The data from national household surveys generally show no significant differences in underweight prevalence between boys and girls. However, these trends should continue to be monitored, particularly at the subnational level and within subgroups of the population.
Indicators of malnutrition generally show differentials between rural and urban settings. In some countries, child nutrition may vary across geographical areas, socioeconomic groups or ethnic groups. However, showing and analyzing data on specific ethnic groups may be a sensitive issue in the country. Gender differences may also be more pronounced in some social and ethnic groups.
International data comparisons
UNICEF and WHO produce international data sets based on survey data. In some countries, ages may have to be estimated.
Comments and limitations
The weight-for-age indicator reflects body mass relative to chronological age and is influenced by both the height of the child (height for age) and weight-for-height. Its composite nature makes interpretation complex. For example, weight for age fails to distinguish between short children of adequate body weight and tall, thin children.
Low height for age or stunting, (below minus two standard deviations from the median height for age of the reference population) measures the cumulative deficient growth associated with long-term factors, including chronic insufficient daily protein intake.
Low weight for height, or wasting, (below minus two standard deviations from the median weight for height of the reference population) indicates in most cases a recent and severe process of weight loss, often associated with acute starvation or severe disease.
When possible, all three indicators should be analysed and presented since they measure and reflect different aspects of child malnutrition.
Ministries of health.
United Nations Children’s Fund.
World Health Organization.