New Zealand children are gaining more weight and becoming less healthy than children in many other countries, a study has found.
Researchers tracked trends in height, weight and body mass of children aged 5 to 19 years in 200 countries over 35 years.
The results, published in The Lancet, suggest Pacific Island children had the highest body mass index in the world in 2019, with New Zealand kids not far behind.
One of the New Zealand authors of the study, Prof Jim Mann, said the results were a serious concern.
"We know, because we've seen it many times before... we're a world leader in childhood obesity and indeed adult obesity," Mann said.
"This study has shown kids in New Zealand have been among the world leaders in gaining far more weight than height.
"This is a really important finding."
Mann, who is director of the Healthier Lives National Science Challenge research centre, said little was being done to tackle childhood obesity in New Zealand.
"We know very little about what kids in New Zealand are eating... we haven't had a survey in New Zealand since 2003.
"We need to do something about it and we really are doing almost nothing about it."
While COVID-19 had understandably been the focus of intense concern, it was worrying that other problems were being neglected, Mann said.
"What we need is for this to be treated as a national epidemic - which it is," he said.
The report's authors said more investment in child and youth health was needed, such as providing healthy school meals and better sports facilities.