Poor diet: Children 20cm shorter as a result

Poor diets for school-age children may contribute to an average height gap of 20cm (7.9in) between the tallest and shortest nations.

The research team analysed data from more than 65 million children and adolescents aged 5 to 19 years from more than 2000 studies between 1985 and 2019.

In 2019, on average, children and teenagers in north-western and central Europe (eg those in the Netherlands and Montenegro) were the tallest in the world. The tallest 19-year-old boys lived in the Netherlands (183.8cm or 6ft)

Meanwhile, the 19-year-olds who were on average the shortest lived in South and South-East Asia, Latin America and East Africa. The shortest lived in Timor Leste (160.1cm or 5ft 3in). 

On average, 19-year-old boys in Laos were the same height (162.8cm or 5ft 4in) as 13-year old boys in the Netherlands.

At 19 years old, girls in Guatemala, Bangladesh, Nepal and Timor Leste were the same average height as 11-year-old Dutch girls (about 152cm or 5ft).

The largest improvements in the average height for children over the last 35 years were seen in China and South Korea.

But in many countries in sub-Saharan Africa, average heights remained unchanged or reduced since 1985.

While researchers acknowledge that genetics play an important part in individual children's height and weight, when it comes to the health of entire populations, nutrition and the environment are the key.

Dr Andrea Rodriguez Martinez from Imperial College London, one of the lead researchers, said healthy weights and heights in childhood and adolescence have lifelong benefits for people's wellbeing. 

She said: "Our findings should motivate policies that increase the availability and reduce the cost of nutritious foods, as this will help children grow taller without gaining excess weight for their height." 

"These initiatives include food vouchers towards nutritious foods for low-income families, and free healthy school meals."