A ground-breaking obesity study that will breath-test thousands of Kiwi schoolchildren is off to a promising start, its leaders say.

The ambitious study, involving about 2000 students in its first year, aims to reveal the role of little-understood sugar fructose in New Zealand's childhood obesity epidemic.

Fructose is the least-understood sugar in our diet, but studies have shown how it's probably a major contributor to metabolic diseases such as obesity and diabetes.

Targeted at schools with high proportions of Maori and Pasifika students, the study will see students taking a simple breath test that measures hydrogen gas to record fructose absorption rates.

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The research team, led by Professor Peter Shepherd of the Auckland University-based Maurice Wilkins Centre, would then use the data to tease out how well Kiwi kids absorb fructose - and what affect it could be having.

It was already known that there was a wide variation in the amount of fructose that individuals could absorb from the gut into the bloodstream.

Those who were good at absorbing fructose were likely to retain more calories from sugar in diets than those who didn't absorb it well, which could explain why some children were more at risk than others.

What the scientists discover could prove crucial in identifying those most at risk from modern food, which would allow targeted interventions.

One third of school-aged Kiwi children were now considered overweight or obese, and one in nine children between 2 and 14 were obese, including 30 per cent of Pacific children and 15 per cent of Maori children.

Figures also showed one in five children living in socio-economically deprived areas were obese, compared with one in 50 children living in the least deprived areas.

Shepherd said his colleagues had already performed brief tests on a small number of Epsom Girls' Grammar students to validate the use of the machines.

A high school teacher working on the project as part of Master of Science studies was also developing curriculum-relevant material that would help teachers carry out the tests.

Tt was too early in the study to reach any scientific conclusions, but Shepherd said results from the few students tested so far revealed a marked difference between individuals, which he considered a "great start".

Shepherd was now looking to expand the programme outside Auckland, initially to Opotiki in the Bay of Plenty, and the Far North.

"We are seeking sites outside the main centres, as this is where the greatest need is, and schools and communities are struggling to get the type of input city schools can get," Shepherd said.

"We chose Opotiki, as we have developed strong links with a Maori group based in that area who are developing community-based programmes to improve health outcomes for Maori."

"In the future we will of course include any school that wants to be involved. Already, more than 40 have expressed strong interest and we have a person going around those schools to see how we can implement the programme."

One researcher has been partially funded to work with the Moko Foundation to roll it out in the Far North, and another has been awarded a Health Research Council grant to bring it to Pacific communities.

The project has also attracted US fructose expert Dr Rick Johnson, who has joined as an adviser, and Cambridge University researchers were interested in replicating it in Europe.