An analysis conducted from studies in a span of 34 years reveals that poor nutrition has greatly contributed to a difference in height and weight for school going children.
The study showed that there was a 20cm difference between countries with the tallest people and those with the shortest people among 19-year olds, of the countries that participated in the study.
For the Body Mass Index (BMI), the difference between countries with the highest and the lowest unit was about nine to 10kg per square metre which equates to about 25kg.
The analysis, which looked at over 2,000 studies and about 65 million children in 200 countries and territories between 1985 and 2019, showed that Netherlands had the tallest boys of about 183.8cm and the shortest boy last year was from East Timor with about 160.1cm.
Again, the tallest girls were from the Netherlands with a height of about 170.4cm while the short girls were from Guatemala and were about 150.9cm.
Generally, countries in northwestern and central Europe had the tallest 19-year-olds. The countries that came after the Netherlands were Montenegro, Estonia and Bosnia and Herzegovina for boys. And, for girls, Montenegro, Denmark and Iceland had the tallest people. "The 20cm or higher difference between countries with the tallest and shortest mean height represents approximately eight years of growth gap for girls and approximately six years for boys," said the researchers.
"For example, 19-year-old girls in four countries (Guatemala, Bangladesh, Nepal and Timor-Leste) had the same mean height as that of 11-year-old Dutch girls, and those in another 53 countries -- such as Burundi, India, Indonesia, Laos, Pakistan, Peru, the Philippines, and Yemen -- had the same mean height as that of 12-year-old Dutch girls.
"Similarly, 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," added the study.
An improvement in the height was recorded in emerging economies such as China (largest gain for boys and third largest for girls) and South Korea (third largest for boys and second largest for girls).
For BMI, countries in the Pacific Island in Oceania had the highest BMI of about 28kg per square metre. "Late-adolescence BMI was also high for boys and girls in Middle Eastern and north African countries such as Kuwait and Bahrain; in Caribbean islands such as the Bahamas; in Chile, the US and New Zealand; and, for girls, in South Africa," the study said.
The lowest average BMI among boys was about 21kg per square metre and was recorded in East and central Africa (Ethiopia and Chad), South East Asia (India, Bangladesh) and South East Asia (Timor-Leste).
The researchers acknowledge that there are several factors that could contribute to the difference in height and BMI of children and adolescents and the genetic aspect could be one of them. But, they say that genetics has very little contribution to the difference, especially for the BMI.
"Genetics has a small role in height and BMI at the population level relative to nutrition and environment is also supported by the finding that the height of migrant descendants typically converges to the height of their new country within a few generations," the study explained.
Onset of puberty
The researchers also highlighted other factors that may have contributed to the variation in height and BMI. "Intergenerational exposures and experiences during pregnancy, age of puberty onset which could be influenced by diet, physical activity, occurrence and treatment of infections, which itself is influenced by water and sanitation, and whether episodes of infections are effectively treated in a timely manner," the study said.
"Finally, all of these pathways are influenced by food and nutrition," the researchers concluded. "Future studies should also evaluate the socioeconomic and geographical patterns of height and BMI in these ages, as has been done for children younger than five years and adults."