New Zealand's high rate of obesity is no surprise, because of its fat-promoting environment and its love affair with cars, an international health leader says.

"It's a normal human response to get fat in the New Zealand environment," Professor Philip James said yesterday.

"Most governments assume it's all your fault if you're fat. But in Britain, the chief scientist's advice, which has been accepted by the Cabinet, is that it's not true."

An adviser to the World Health Organisation and president of the International Association for the Study of Obesity, the London nutrition expert was invited by AUT University to lecture in Hamilton and Auckland.

Professor James said that in countries such as Britain and New Zealand, the reason for many people's obesity was a genetic predisposition in an environment which allowed it to happen with an "out-of-control" food industry and the constant use of cars.

The food industry denies it is out of control, citing voluntary improvements by manufacturers which have removed tonnes of sugar, salt and saturated fat from diets.

A quarter of New Zealand adults are obese, one of the highest rates in the West and an increase of 150 per cent since 1980.

But there is evidence the obesity rate among children has stabilised at around 9 per cent. Maori, Pacific and poor people have higher rates.

Professor James said New Zealand's obesity controls had fallen behind the rest of the Western world.

He advocates strict controls in schools, a coloured food-labelling system, a ban on food marketing to children, tax breaks for fruit and vegetables and more cycleways.

Professor James said he was astonished that the National Government ditched the rule allowing only healthy foods to be sold routinely in schools.

Health Minister Tony Ryall favours an educational rather than a rule-based approach to nutrition.

But the professor said New Zealand was going against the world trend, even among conservative governments. Its policy amounted to a subsidy for bad foods and taught children that eating them was normal.

He said obesity and the diseases it causes - such as heart disease, diabetes and some cancers - would overwhelm health services without major changes.

Simply telling people about healthy eating and activity was of limited value as educational methods worked only on the well educated.

* Ban junk food from state-owned premises.
* Reduce GST on fruit and vegetables and increase it on foods high in sugar, salt and saturated fat.
* Introduce coloured "traffic light" labels to grade packaged foods for consumers from healthy to unhealthy.
* Ban food marketing to children.
* Establish food and activity requirements for school.