Health experts are horrified, warning that gains to life expectancy could be reversed if drastic action is not taken.

It needs an effort along the lines of the anti-smoking campaign, says Professor Graeme Hankey, co-author of the report which was published in The Lancet medical journal on Thursday.

The 188-country report shows Australia's problem is ballooning out of control.

Overall 63 per cent of adults are overweight, up from 49 per cent in 1980. Five million, one third of the adult population, are obese.

One in four children are overweight. New Zealand is worse, with 66 per cent of adults overweight. When grouped together, Australians and New Zealanders are becoming obese at a faster rate than any other region.

"We should be incredibly worried," said Prof Hankey of the University of Western Australia.

Other developed countries are starting to plateau, he said, but not Australia and New Zealand.

"We are getting worse."

Apart from the burden of diabetes, heart disease and stroke, people are buckling under the strain.

"It causes wear and tear on the knees, hips and spine from having to carry the weight around," Prof Hankey said.

"We seem to have nailed tobacco and reversed the trend, but we are not doing very well at managing this."

The study was led by Professor Emmanuela Gakidou from the Institute for Health Metrics and Evaluation at the University of Washington.

“Unlike other major global health risks, such as tobacco and childhood nutrition, obesity is not decreasing worldwide," he said.

"Our findings show that increases in the prevalence of obesity have been substantial, widespread, and have arisen over a short time. However, there is some evidence of a plateau in adult obesity rates that provides some hope that the epidemic might have peaked in some developed countries and that populations in other countries might not reach the very high rates of more than 40% reported in some developing countries."

But the Heart Foundation's Dr Robert Grenfell said Australia was going backwards on obesity.

"Overweight and obesity is now one of the leading causes of preventable death and disease in our community. Carrying the extra kilos greatly increases the risk of death from heart disease."

Professor Rob Moodie of the Melbourne School of Population Health blamed junk food and a sedentary lifestyle.

"The environment is geared towards over-consumption because of the way food is marketed and because of a lack of regulation," he said.

"The junk food and processed food industry is enormously powerful. The politicians are absolutely frightened."

It's marketed all over sport and social media, he said.

"The exposure of children to junk food and junk drink advertising needs to be reduced."

Key findings from study:

In the developed world, men have higher rates of obesity than women. The opposite is true in developing countries.

The prevalence of childhood obesity has rapidly increased in developed countries, from 17 per cent in 1980 to 24 per cent in 2013 in boys; and from 16 per cent to 23 per cent in girls.

Especially high rates of overweight and obesity have already been reached in Tonga where levels of obesity in men and women exceed 50 per cent.

More than 50 per cent of women are obese in the Kuwait, Libya, Qatar, and the Pacific Islands of Kiribati

A short-term goal should be to reduce the amount of salt, fat and sugar in processed food as well.

"If you do it across the board, it reduces the risk for the whole population.

"We need sensible regulation to make sensible choices much easier than they are at the moment."

Australia and New Zealand are ranked the 30th and 23rd most overweight countries in the world, not far behind the US, which is ranked 20th.

In the US, close to three quarters of men and six in 10 women are overweight or obese.

"In the last three decades, not one country has achieved success in reducing obesity rates, and we expect obesity to rise steadily unless urgent steps are taken," said co-author Christopher Murray of the University of Washington.