New Zealand's 4-year-olds appear to be resisting the rising tide of obesity - now considered an epidemic threatening to weigh down our health system according to a University of Otago-linked study.
Researchers have trawled national data and found a slight decline in the rate of overweight or obese children of that age group - although it wasn't clear whether that changed after they started school.
The just-published finding was nonetheless one piece of welcome news at a time when one in three children aged between 4 and 5 were overweight or obese - a rate that rose to 50% of Pasifika children, and 40% for those in low socio-economic areas.
Among OECD countries, New Zealand now ranked 4th out of 34 countries for children between 2 and 19 years who are overweight and obese - immediately behind the United States.
Researchers collaborating under A Better Start, one of New Zealand's National Science Challenges, analysed data from the B4 School Check, a health check conducted each year on the country's 4-year-olds.
They found that there had been a 2.2% decline in the number of youngsters who were overweight, obese or extremely obese between 2010 and 2016.
The decline was across the board, spanning gender, ethnicity, urban and rural children, and even socioeconomic status.
While there was a need to monitor whether the trend held up over time, the figures were in line with international reports of decreasing child obesity prevalence from developed countries such as the US, Singapore, some parts of Europe and the UK.
"The research has found a small decline in what has been a rising tide of obesity in our children," said the study's lead author Dr Nichola Shackleton, of the University of Auckland.
"While that's good news for 4-year-olds, we don't know if this effect continues once they reach school."
The research was a collaboration between the Challenge Healthy Weight and Big Data research teams at Auckland, Otago and Massey universities, and Uppsala University in Sweden.
Over the six years, the B4 School Check was completed by registered nurses on between 75% and 92% of 4-year olds, about 317,000 children.
The science challenge's director, Professor Wayne Cutfield, of the Auckland University-based Liggins Institute, said the decline might indicate that health promotion was working on families with young children.
For young children, families had easier access to physical activities and better control on what they eat.
"This adds to the picture we have on child obesity," Cutfield said.
"It's a priority research theme for the challenge because not having a healthy weight is a leading factor preventing children from going on to lead healthy and successful lives."
Obesity was linked to a long list of health conditions, including heart disease, type 2 diabetes and some forms of cancer, and now contributed to about 9% of all illness, disability and premature death.
Challenge co-director Professor Barry Taylor, of University of Otago, said the research also showed the power of the Integrated Data Infrastructure, the project to bring publicly gathered data together for research.
"By matching the B4 School Check data with Census information, it has been possible to generate community level information that can be shared to lift the health of their neighbourhoods," he said.
The current main source of data on childhood obesity comes from the National Health Survey, which relied on data from fewer than 5000 children, aged from birth to 14.
The study was the first of 11 planned over the next two years that looked at links between early life events and childhood obesity.
Those included being born early, late, too small, too large, at increased maternal age, or exposed to maternal antibiotics during pregnancy and in early childhood.
The OECD country with the biggest child obesity problem is Chile, affecting 31.6% of boys and 37% of girls.