Can poor diet stunt growth? Study suggests it may have caused a 20cm difference in height across countries
Poor nutrition among school-aged children may have created a 20 cm gap in height among the tallest and the shortest nations. This is according to a global analysis that examined the height and weight of school-aged children and adolescents — which are indicators of their health and quality of their diet — across the world and found that they vary enormously.
Led by Imperial College London, the authors suggest that the 20 cm difference between 19-year-olds in the tallest and shortest countries represents an eight-year growth gap for girls and a six-year growth gap for boys. They warn that highly variable childhood nutrition, especially a lack of quality food, may lead to stunted growth and a rise in childhood obesity, thus affecting a child’s health and wellbeing for their entire life.
The analysis used data from 65 million children aged five to 19 years old in 193 countries. The data was reported from 1985 to 2019. Nations with the tallest 19-year-olds in 2019 were in the northwest and central Europe. It includes the Netherlands, Montenegro, Estonia, and Bosnia and Herzegovina for boys; and the Netherlands, Montenegro, Denmark, and Iceland for girls.
The nations with the shortest 19-year-olds in 2019 were mostly in south and southeast Asia, Latin America and East Africa. This includes Timor-Leste, Laos, Solomon Islands, and Papua New Guinea for boys; and Guatemala, Bangladesh, Nepal and Timor-Leste for girls.
“We identified highly variable age trajectories and trends over time in the height and BMI of school-aged children and adolescents across countries and territories. These cross-country differences show that childhood and adolescence are crucial periods in differentiating countries in terms of how they shape these determinants of lifelong health,” write researchers in the study published in The Lancet.
The analysis, for example, suggests that 19-year-old boys in 11 countries throughout Asia, Latin America, and sub-Saharan Africa had the same mean height as that of Dutch boys aged 13 years. Similarly, the average 19-year-old girl in Bangladesh, Guatemala, Nepal, and Timor-Leste had the same height as an average 11-year-old girl in the Netherlands.
Healthy and unhealthy weight gains
The investigators also assessed children’s Body Mass Index (BMI) — a measure of the height to weight ratio, which indicates whether a person has a healthy weight for their height. The results show that 19-year-olds with the largest BMI were found in the Pacific islands, the Middle East, the US, and New Zealand. The BMI of 19-year-olds was lowest in south Asian countries such as India and Bangladesh. The difference between the lightest and the heaviest BMIs in the report was around 9 units of BMI, which is equivalent to around 25 kg of weight.
According to the researchers, in many nations, children at age five had a height and weight in the healthy range defined by the World Health Organization (WHO). However, after this age, children in some countries have experienced too small an increase in height, and gained too much weight, compared to the potential for healthy growth. The team says the most important reason for this is the lack of adequate and healthy nutrition and living environment in the school years, as both height and weight gains are closely linked to the quality of a child’s diet.
“Children in some countries grow healthily to five years, but fall behind in school years. This shows that there is an imbalance between investment in improving nutrition in pre-schoolers, and school-aged children and adolescents. This issue is especially important during the Covid-19 pandemic when schools are closed throughout the world, and many poor families are unable to provide adequate nutrition for their children,” explains the senior author of the study Professor Majid Ezzati from Imperial’s School of Public Health.
When changes in both height and BMI were considered, girls in South Korea, Vietnam, Saudi Arabia, Turkey, and some central Asian countries (such as Armenia and Azerbaijan), and boys in central and western Europe (for example, Portugal, Denmark, Poland, and Montenegro) had the healthiest changes over the past 3.5 decades. This is because, compared with children and adolescents in other countries, they had a much larger gain in height than they did in BMI.
“The unhealthiest changes — gaining too little height, too much weight for their height compared with children in other countries, or both — occurred in many countries in sub-Saharan Africa, New Zealand, and the US for boys and girls; in Malaysia and some Pacific island nations for boys; and in Mexico for girls,” the findings state.
Dr Andrea Rodriguez Martinez, the lead author of the study from Imperial's School of Public Health, emphasizes that the findings should motivate policies that increase the availability and reduce the cost of nutritious foods, as this will help children grow taller without gaining excessive weight for their height. “These initiatives include food vouchers towards nutritious foods for low-income families and free healthy school meal programs, which are particularly under threat during the pandemic. These actions would enable children to grow taller without gaining excessive weight, with lifelong benefits for their health and wellbeing,” suggests Dr Martinez.