Taylor Wilcox

EXPERT REACTION: Kiwi kids among the unhealthiest in the world

Embargoed until: Publicly released:
Peer-reviewed: This work was reviewed and scrutinised by relevant independent experts.

Simulation/modelling: This type of study uses a computer simulation or mathematical model to predict an outcome. The original values put into the model may have come from real-world measurements (eg: past spread of a disease used to model its future spread).

A worldwide study of children aged 5-19 years found that kids in New Zealand are gaining more weight, and becoming less healthy, than many other countries. Researchers analysed data from 200 countries to track trends in height, weight and BMI from 1985 to 2019. The results suggest Pacific Island kids had the highest BMI in the world in 2019, with NZ not far behind. The authors say more investment is needed for school-aged kids and teenagers, such as free healthy school meals and better sports facilities.

Journal/conference: The Lancet

Organisation/s: University of Otago, University of Auckland, The University of Sydney, The University of Queensland, The University of Adelaide

Funder: The NCD-RisC database was supported by a Biomedical Resource and Multi-user Equipment Grant from the Wellcome Trust (101506/Z/13/Z) and was expanded to include children and adolescents with partial support by a charitable grant from AstraZeneca Young Health Programme. The analysis in this paper was partly supported by the STOP project which received funding from EU Horizon 2020 research and innovation programme under Grant Agreement 774548.

Media release

From: Healthier Lives National Science Challenge

A new comprehensive global study suggests there are concerning height and Body Mass Index (BMI) trends among school-aged children and adolescents.

The authors are calling for global health and nutrition programmes to be extended to school-aged children and adolescents to enable healthy growth throughout development.

Just published in The Lancet, the large global study was undertaken by a huge number of researchers over 35 years, and pooled data from more than 2,000 population-based studies, with measurements of height and weight in 65 million participants in 200 countries.

The researchers analysed child and adolescent physical growth trends and found wide variations in height and BMI among school-aged children, and faltering growth in many countries, most likely due to lack of adequate and healthy nutrition during school years.

The study found that unhealthy growth trends – with too little height gain and/or excess weight gains – were seen in several countries including New Zealand, the USA, Malaysia, Mexico and sub-Saharan Africa.

Unhealthiest changes – gaining too little height, or too much weight for their height compared with children in other countries, or both of these – occurred in many countries, including for boys and girls in New Zealand, and for boys in some Pacific Island nations.

This study follows hard on the heels of the UNICEF’s annual Innocenti report card which named New Zealand adolescents as some of the most overweight in the OECD. Out of 41 OECD and EU countries, New Zealand was ranked second-to-worst for childhood obesity.

One of the New Zealand authors, Professor Jim Mann, who is Director of Healthier Lives National Science Challenge and the Edgar Obesity and Diabetes Research Centre (EDOR) has said that obesity is a “silent killer” pandemic and this study shows that the issue is escalating in New Zealand.

A pressing issue is the lack of nutrition data in New Zealand. He and others have called for a national nutrition survey to be carried out immediately.

“New Zealand has not had a survey since 2002 so we don’t actually know what New Zealanders are consuming.”

“We have also called for school-based healthy food and drink policies and this study reinforces the need for such policies as well as restrictions on advertising unhealthy foods to children,” he says.

Besides Professor Mann, several New Zealand experts in non-communicable diseases and nutrition were part of the study, including Associate Professor Rachael McLean from the University of Otago and Honorary Associate Professor Winsome Parnell and Jody Miller.

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  • The Lancet
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Expert Reaction

These comments have been collated by the Science Media Centre to provide a variety of expert perspectives on this issue. Feel free to use these quotes in your stories. Views expressed are the personal opinions of the experts named. They do not represent the views of the SMC or any other organisation unless specifically stated.

Elaine Rush is Emeritus Professor of Nutrition at Auckland University of Technology.

Height, weight and BMI normally increase with age in school age children. It is true that between 1985 and 2019, New Zealand has an unacceptably high and increasing prevalence of excess body weight and rapid growth in our tamariki. This is associated with poverty, food insecurity and is higher in Māori and Pacific children. A greater proportion of Māori and Pacific children live in areas of deprivation than European and Asian children. This is recorded in the annual reports of the New Zealand Health Survey. 

What the analysis undertaken by the Non-Commmunicable Disease Risk Factor collaboration does not take into account is the increasing ethnic diversity of the New Zealand child population and how that has changed between 1985 and 2019. One size does not fit all.

The major ethnic groups are Māori (the Indigenous people) 17%, Pacific 8%, European 70% and Asian 15%. This adds up to more than 100% because many identify with more than one ethnic group. European is an aging population, with 20% of both the European and Asian populations aged between five and 19 years, while Pacific and Māori each have 33% of their population between five and 19 years.

When comparing them at the same age, Pacific and Māori children weigh more than European and Asian for the same body mass index. However, Māori and Pacific children have less fat and more muscle than European and Asian children. Pacific and Māori children are taller and mature earlier than European children, but by age 19 there is little difference in height.

The authors, in the discussion, say that these measures differentiate countries in terms of how they shape determinants of lifelong health. No measures of health, ethnic differences in shape and size, socioeconomic status or food security were assessed. The highest prevalence of type 2 diabetes in New Zealand occurs in Pacific, Māori and Asian, not European. Yet Pacific and Asian are the two extremes of BMI, weight and height measures. Body size and growth trajectories are imperfect measures of ‘nutritional quality and lifelong health advantages and risks’ of Indigenous, multiethnic and migratory populations.

Last updated: 06 Nov 2020 9:11am
Declared conflicts of interest:
No conflict of interest.

Collin Tukuitonga is Associate Professor of Public Health at the University of Auckland.

This is a huge study comparing 65 million school-aged children across 200 countries and territories pooling data from 2,181 population-based studies over 34 year period 1985-2019.  It is the first study of this kind comparing age trajectories and time trends in mean height and mean BMI.  It is an important study because it is a rare study of older children and adolescents across several countries.

The study includes sixteen Small Islands Developing States from the Pacific region but the authors acknowledge that there were fewer data sources form this region leading to larger uncertainty of the estimates.

Estimates confirm much of what is already known e.g. BMI was highest in 19 year-old Pacific Island boys often surpassing 28kg/m2. Conversely, boys from PNG and Solomon Islands were among the shortest in the world. A number of unhealthy trends were reported e.g Pacific Island boys and those from New Zealand were among those gaining too much weight for height.

Study findings have important implications for nutrition policies in NZ and the Pacific Islands including considerations for agriculture and food policies.

Last updated: 06 Nov 2020 9:11am
Declared conflicts of interest:
No conflict of interest.

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