Global study examines impact of childhood nutrition on height, BMI

Researchers at the Imperial College London looked at millions of school-aged children and found that their height and weight vary enormously around the world. 

The study

The analysis, published in journal The Lancet,​ used data from 65 million children aged five to 19 years old across 193 countries.  They assessed the height and weight of school-aged children using data reported from 1985 to 2019. 

Findings

The study revealed a 20 cm (7.8 in) difference between 19-year-olds in the tallest and shortest nation, representing an eight-year growth gap for girls and a six-year growth gap for boys. For instance, the study found the average 19-year-old girl in Bangladesh and Guatemala (nations with the world's shortest girls) is the same height as an average 11-year-old girl in the Netherlands (the nation with the tallest boys and girls.)

The analysis also found that the nations with the tallest 19-year-olds in 2019 were in northwest and central Europe, and included the Netherlands, Montenegro, Denmark and Iceland.

The nations with the shortest 19-year-olds in 2019 were mostly in south and southeast Asia, Latin America and East Africa, including Timor-Leste, Papua New Guinea, Guatemala and Bangladesh.

New heights 

The largest improvements in average height of children over the 35-year period were seen in emerging economies such as China, South Korea and some parts of southeast Asia. For example, 19-year old boys in China in 2019 were 8 cm (3.1 inches) taller than in 1985, with their global rank changing from 150th tallest in 1985 to 65th in 2019. In contrast, the height of children, especially boys, in many Sub-Saharan African nations has stagnated or reduced over these decades.

In the UK, even though 19-year-olds are taller now than they used to be, other nations gained faster over the past 35 years.  The UK's global height ranking fell from 28th tallest in 1985 (176.3 cm) to 39th in 2019 (178.2 cm), and 19-year-old girls from 42nd (162.7 cm) to 49th (163.9 cm).

Tracking BMI

The study also assessed children's height to weight ratio. The analysis found that 19-year-olds with the largest body mass index (BMI) were located in the Pacific islands, Middle East, 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 study was 55 lbs. 

The authors observed in many nations that 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 did not increase enough in height and gained too much weight. 

The authors explained the 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:

“Our findings on the heterogeneous age trajectories and time trends of height and BMI in late childhood and adolescence raise the need to rethink and revise two common features of global health and nutrition programs. First, we need to overcome the disconnect in research and practice between reducing undernutrition, particularly short stature, and preventing and managing overweight and obesity. Second, the finding that children in some countries grow healthily to age 5 years but do not continue to do so during school years shows an imbalance between investment in improving nutrition and growth before age 5 years and doing so in school-aged children and adolescents.”​

Professor Majid Ezzati, senior author of the study from Imperial's School of Public Health, said childhood nutrition, especially amid a pandemic, has never been more important. 

"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 preschoolers, and in 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,”​ explained Ezzati. 

Dr. Andrea Rodriguez Martinez, the lead author of the study from Imperial's School of Public Health, added that the findings should motivate policies that increase the availability and reduce the cost of nutrition in order to 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.”​

Tallest 10 countries for boys in 2019 (age 19)

Netherlands (183.8 cm), Montenegro (183.3 cm), Estonia (182.8 cm), Bosnia and Herzegovina (182.5 cm), Iceland (182.1 cm), Denmark (181. 9 cm), Czech Republic (181.2 cm), Latvia (181.2 cm), Slovakia (181.0 cm), Slovenia (181.0 cm)

Shortest 10 countries for boys in 2019 (age 19)

Timor-Leste (160.1 cm), Lao PDR (162.8 cm), Solomon Islands (163.1 cm) , Papua New Guinea (163.1 cm), Mozambique (164.3 cm), Guatemala (164.4 cm), Nepal (164.4 cm), Yemen (164.4 cm), Bangladesh (165.1 cm), Madagascar (165.2 cm)

Tallest 10 countries for girls in 2019 (age 19)

Netherlands (170.4 cm), Montenegro (170.0 cm), Denmark (169.5 cm), Iceland (168.9 cm), Latvia (168.8 cm), Estonia (168.7 cm), Serbia (168.3 cm), Czech Republic (168.0 cm), Lithuania (167.6 cm), American Samoa (167.6 cm)

Shortest 10 countries for girls in 2019 (age 19)

Guatemala (150.9 cm), Bangladesh (152.4 cm), Nepal (152.4 cm), Timor-Leste (152.7 cm), Madagascar (153.1 cm), Lao PDR (153.1 cm), Philippines (154.1 cm), Maldives (154.3 cm), Indonesia (154.4 cm), Peru (154.4 cm)

10 countries with highest BMI in 2019 for boys (age 19)

Cook Islands (29.6), Nauru (29.5), Tuvalu (28.2), Niue (28.1), Tonga (27.3), American Samoa (27.2), Tokelau (27.2), Palau (27.1), French Polynesia (26.3), Kiribati (26.2)

10 countries with lowest BMI in 2019 for boys (age 19)

Ethiopia(19.2), Niger (19.8), DR Congo (19.9), Senegal (20.1), India (20.1), Timor-Leste (20.3), Bangladesh (20.4), Central African Republic (20.5), Nepal (20.5), Chad (20.6)

10 countries with highest BMI in 2019 for girls (age 19)

Tonga (29.0), Cook Islands (28.9), Nauru (28.6), Niue (28.3), Tokelau (27.9), Samoa (27.9), Tuvalu (27.2), American Samoa (26.6), Palau (26.5), French Polynesia (26.2)

10 countries with lowest BMI in 2019 for girls (age 19)

Timor-Leste (19.6), Romania (19.9), India (20.1), Viet Nam (20.4), Madagascar (20.4), Sri Lanka (20.6), Cambodia (20.6), Myanmar (20.6), Bangladesh (20.6), Japan (20.6)

Source: The Lancet ​

VOL 396, ISSUE 10261, P1511-1524, NOV 07, 2020 DOI: doi.org/10.1016/S0140-6736(20)31859-6​

“Height and body-mass index trajectories of school-aged children and adolescents from 1985 to 2019 in 200 countries and territories: a pooled analysis of 2181 population-based studies with 65 million participants”​

Authors: M. Ezzati et al.