New modelling shows a 30 per cent reduction in kilojoules in all sugar-sweetened drinks would not only reverse Australia's obesity crisis, but drastically reduce the number of people succumbing to obesity-related diseases such as stroke, type 2 diabetes and kidney cancer.

"The results are a clear demonstration of the harm sugary drinks are causing," said lead researcher Michelle Crino, from the George Institute for Global Health.

"The reduction would deliver cost savings of $8 billion and avert at least 155,000 premature deaths, including 47,000 from type 2 diabetes alone."

Sugary drinks have been targeted by health campaigners in the battle against the bulge because they are energy dense and nutrient poor, filling consumers up with calories but leaving them feeling hungry.

Empty calories can lead to weight gain. Obesity is a leading risk factor for a host of diseases.

The study, published in the latest Nutrients journal, found "reformulation" would prevent 70,300 deaths from heart disease, 47,000 deaths from type 2 diabetes, 14,300 deaths from stroke, and 24,100 deaths from breast, bowel cancer, endometrial and kidney cancers, over the lifetime of the 2010 Australian population.

The researchers calculated the likely changes in weight and therefore changes in Body Mass Index at the population level for each type of intervention.They then plugged the BMI data into an "obesity" model that quantified changes in the total mortality and morbidity of the 2010 Australian population to estimate "health-adjusted life years".If sugar content dropped by 5 per cent, about 26,400 deaths would be averted, the researchers found. If all single-serve sugary drinks were capped at 375ml, the number would fall to 13,495.

"If the government is not going to implement a sugar tax, then we urge them to adopt one of our interventions," Ms Crino said.

"We found government-imposed legislative scenarios, rather than voluntary pledges, would provide more cost savings and bigger health gains."

The researchers looked at sugar-sweetened soft drinks, flavoured waters, iced teas, sports drinks and cordials, but excluded fruit drinks and juices from their calculations.

Two-thirds of Australian adults and one in four children are overweight or obese, according to the Australian Bureau of Statistics.

The intervention calls come amid a renewed push for a tax on sugary drinks – as has occurred in Ireland last week – but the federal government remains firmly opposed to it.

A soft drink tax and reformulation targets for manufacturers are among eight policy actions underpinning the Tipping the Scales strategy, which the Obesity Policy Coalition is urging the government to adopt.

The Australian Beverages Council said the public should be "deeply sceptical" of the "policy-driven" study, which it claims ignores its efforts to reduce sugar. It's fighting the tax.

"For many years, we pioneered a wealth of measures to reduce sugar consumption, including smaller pack sizes, product reformulation and ever-increasing low- and no-calorie options," said its chief executive Geoff Parker.

"For 15 years, without any government intervention, sales in the water-based beverage category have been moving away from regular sugar varieties," he continued.

"Across that period, sugar contribution from soft drinks has decreased per person by 26 per cent."

Coca-Cola Amatil, for example, has cut the sugar content of Deep Spring by 26 per cent and Lift by 23 per cent, as part of its "systematic reformulation plan".

But the Obesity Policy Coalition said the findings were evidence the government must pass legislation for mandatory reformulation.

"Voluntary initiatives don't always work well ... we've seen companies reformulate a product, see a decrease in sales and go back to the old formulation," said its executive manager Jane Martin.

"It needs to be mandatory because the gains are greater, you can push the industry to move faster, it creates a level playing field and certainty."

The Health Department didn't answer questions about the findings and instead outlined its approach in tackling the obesity epidemic.

It pointed to the existing dietary guidelines, absence of GST on fruit and vegetables, Health Star Rating scheme, Healthy Food Partnership with industry and health groups, among other measures.

"The government announced in the 2017-18 budget additional funding of $15 million over four years to increase support for people's activity levels and encourage healthy lifestyles to prevent chronic disease," a spokeswoman said.

But the Australian Medical Association NSW said it has seen almost nothing from the government related to healthy eating.

"I find this quite disturbing because there is no one solution that will solve this health crisis," said its president Professor Brad Frankum. "It cannot afford to continue to reject the idea of a sugar tax."

A new survey has found 92 per cent of Australians believe obesity is a serious public health problem and nearly 90 per cent support government intervention.

"Seventy per cent agreed the government should regulate food and beverage advertising ... and 55 per cent for taxing sugar-sweetened beverages," said lead researcher Professor Stephen Colagiuri from the Boden Institute of Obesity at Sydney University.

"These results show ... the government is out of step with public opinion."

Professor Bruce Neal from the George Institute said it all boiled down to corporate responsibility.

"Industry could implement these changes within 12 months," he said.

"The effects would be immediate and profound – thousands living healthier lives, free of the symptoms of obesity and tooth decay, and at much reduced risks of stroke, heart disease and type 2 diabetes."