Stunting, which can cause irreversible physical and cognitive effects, affects at least 155 million children globally.

At least 155 million children in the world are stunted.

Chronic malnutrition results in stunting, a condition characterized by a reduced growth rate during childhood that also indicates effects on the child’s cognitive, emotional and physical development. These impacts are often irreversible, creating long-lasting effects on the individual, the family and – on a larger scale – on a country’s overall economy.

According to the World Health Organization (WHO), stunting occurs when a child fails to grow appropriately for his or her age. A child is stunted when his or her growth is slower than the normal rate, as determined by the WHO child growth standards. As a result, a stunted child is too short for his or her age.

Although the exact causes of stunting are still being investigated by the international nutrition community, the main factors are maternal health during pregnancy, child nutrition, dietary quality, prevalence of noncommunicable diseases and factors such as contaminated water and lack of sanitation, among others.

Measuring the prevalence of stunting is also difficult. Lack of access to and availability of child growth checkups at public health facilities mean that height and growth are not regularly tracked for many children in resource-poor settings.

At an individual level, stunting affects the likelihood that a child will remain in school, the wages he or she will earn upon entering the workforce and, for women, their ability to bear healthy children.

On a broader scale, stunting also handicaps the economic productivity of a community or a country. Studies have recently estimated that stunting can cost countries up to 11 percent of their annual GDP.

In 2016, the global prevalence of stunting was 22.9 percent, reduced from 32.7 percent in 2000, according to UNICEF. Even at this improved rate, one in every five children in the world is stunted. The prevalence is also highest in some of the poorest and least developed countries. Southern Asia and sub-Saharan Africa accounted for three-quarters of children under 5 with stunted growth in 2016. Thirty-seven countries bear 85 percent of the global burden.

The second United Nations sustainable development goal commits the global community to end hunger, achieve food security and improved nutrition and promote sustainable agriculture by 2030. It also includes a target to reduce the global prevalence of stunted children from the current 155 million to 100 million by 2025. However, global population growth trends and rates of stunting reduction indicate that this goal will not be reached.

One of the challenges in reaching the target is that more needs to be learned about which interventions work and which determinants cause stunting in the first place. What we know indicates that reducing stunting is a complex and difficult process, given its multifaceted causes and prolonged effects. Success stories do exist, though. Countries that have significantly reduced stunting prevalence have not only used evidence-based interventions tied to nutrition – such as micronutrient supplements and improved feeding practices – but also addressed contextual issues such as poverty.

Vertical programs that focus only on nutrition do not solve the problem of stunting. Nepal’s success in reducing stunting has been attributed to its multifaceted approach involving improved health, education and sanitation measures.

The World Bank estimates that it will cost approximately $8.50 per child under 5 per year over the next 10 years to meet the global target of reducing the number of stunted children to 100 million by 2025. Though this amount – almost $50 billion – is modest compared to global health spending, many countries have not invested sufficiently in nutrition or other programs to noticeably reduce stunting. Only $4.7 billion is currently being spent on general nutrition and stunting-specific interventions in the 37 high-burden countries, according to the World Bank.

This is despite the fact that there is a strong case to be made for investing in stunting reduction. According to the World Bank, $1 invested in reducing stunting generates roughly $16 in economic returns.