New research shows that New Zealand men have been getting fatter faster than males in any other country since the 1980s.
The study, conducted by a group of international researchers, was led by the University of Washington and compared obesity trends between countries over time.
It formed part of the Global Burden of Disease Study and was published in the Lancet on Thursday.
The analysis of trend data from 188 countries found that between 1980 and 2013, the proportion of obese men in New Zealand increased more than in any other country, from 13 percent to 28 percent.
It found that New Zealand's adult overweight and obesity rate jumped from 50 percent to 66 percent over the past 33 years, while the rate of overweight and obese children has risen from 18 percent from 29 percent.
An estimated 2.2 million adults are overweight, and 960,000 of them are obese - meaning New Zealand has the highest rate of obesity in both adults and children in Australasia.
Those with a Body Mass Index (BMI) or a weight-to-height ratio of between 25 and 29 were considered overweight and those with a BMI of more than 30 considered obese.
Currently, half of all overweight women are obese, while nearly a third of children are overweight or obese.
Otago University public health researcher Nick Wilson said the jump in the number of obese men from 13 percent to 28 percent was alarming, and that poor nutrition and a lack of exercise were the presumed causes.
"That particular (gender) difference hasn't really been in the public eye before. It is actually quite a bit higher than the increase for Australia, our near neighbour, so potentially we need to look at lessons from Australia in terms of how to control the obesity problem."
Report co-author Professor Valery Feigin, from Auckland University of Technology, said the comparative figures should be cause for concern.
"Being overweight is a well-established risk factor for stroke, heart attack, dementia and cancer - the four major causes of death and disability in New Zealand. Therefore, the fact that New Zealand has the highest rates of adult and child obesity in the region is very alarming."
He said the results showed that the current strategies for maintaining a healthy weight were not working and that action was urgently needed at a government and individual level.
Researchers say health risks such as cardiovascular disease, cancer, diabetes, osteoarthritis and chronic kidney disease increase when a person's BMI is more than 23.
The research found that while the percentage of people world-wide who are either overweight or obese has risen substantially over the last 30 years, there have been marked variations across regions and countries.
In developed countries, increases in obesity that began in the 1980s and accelerated from 1992 to 2002 have slowed since 2006.
However, in developing countries, where almost two-thirds of the world's obese people currently live, increases are likely to continue.
No countries have had significant decreases in obesity in the last 33 years.