A major cause of New Zealand's very high rates of obesity has been mapped in a world-first study from Auckland University

Researchers have looked at food composition, labelling, and marketing, and found that food environments are predominantly unhealthy.

They've also deduced the policies and actions by government and the food industry to improve the healthiness of food environments, are relatively weak.

Professor Boyd Swinburn has led the three year study funded by the Health Research Council and the Heart Foundation.

He says people choose their diets from the food environments around them and when these are dominated by unhealthy foods and drinks, it's no surprise our obesity rates are so high.

Swinburn adds food labelling is also a problem with slow uptake of the Health Star Rating system and many unhealthy foods carrying positive nutrition claims.