Health experts say a better method is needed to decide which foods and drinks can be marketed to children and which are too unhealthy.
Writing in the New Zealand Medical Journal, Auckland University nutrition expert Cliona Ni Mhurchu said a World Health Organisation (WHO) system for deciding whether foods and drinks are healthy should underpin a revised code on marketing them to children.
One in nine children in New Zealand are obese and a further 22 percent overweight.
Marketing or promotion of foods to children is governed by the Advertising Standards Authority, which is set to release findings of a review shortly.
The authority would not disclose the outcome of its third review in a decade of the codes on advertising to children, including on food.
Chief executive Hilary Souter said it had asked for comment on whether there was a role for a nutrient profiling system and suggestions on which system it should use.
She said it would likely release a revised code in the next two or three weeks.
Prof Ni Mhurchu said the WHO system was better than current options, including the Health Star Rating system introduced two years ago, and the Ministry of Health's Food and Beverage Classification.
"It excludes foods that we wouldn't want to be marketed to children, like sugary breakfast cereals and fruit bars and sugary drinks," she said.
"Whereas the other systems, because they were developed for different purposes - unless they were modified quite a bit - would allow foods to be marketed to children that are not considered with healthy diets and reducing obesity rates."
She said the WHO model would only permit marketing of 33.5 percent of New Zealand breakfast cereals used in her analysis.
The Health Star Rating system, which involves voluntarily labelling food with nutritional information, would permit marketing of 77 percent, while the Ministry of Health's system - which governs food available in schools - would allow 75 percent.
No matter which system was adopted, Prof Ni Mhurchu said independent monitoring would also be needed to see if it had an effect on the foods being marketed to children.
"Because if it doesn't, then that's when we really do need to be considering regulation."
She said evidence suggested regulation was more effective.
She was backed by population health professor Boyd Swinburn, who said the WHO system was designed for marketing to children and New Zealand should adopt it unless there was a good reason not to.
"There's no evidence that any voluntary codes work, internationally, to restrict marketing to children," he said.
"And this one would need to be very tight and well evaluated before, I think, the health community would believe that it is doing a sufficient job to protect children."
However, implementing the WHO system would not be the end of the battle, he warned.
"If this comes in then companies will start just marketing their brand rather than their foods, and so the next challenge will be to say 'Is this an unhealthy brand or not'."