Data showing two in three Australians will be overweight or obese by 2030 highlights the urgent need for a tax on sugary drinks to prevent disease and save lives, the peak doctors' body says.

A data analysis recently released by the Australian Institute of Health and Welfare (AIHW) shows 64 per cent of Australians are likely to be overweight or obese by 2030.

The Australian Medical Association says the figures show obesity is the second biggest modifiable risk factor contributing to the disease burden in Australia after tobacco.

It says the analysis indicates obesity will result in 13,400 preventable deaths.

AMA president Stephen Robson says a tax on sugary drinks would be a step in the right direction to reduce obesity and chronic disease.

"Evidence from overseas shows that a sugar tax is an effective way to reduce sugar consumption and improve health outcomes," Professor Robson said in a statement.

He said the AMA's pre-budget submission launched on Sunday outlined how a tax would have a positive impact on health outcomes and the budget.

"A tax of 40 cents on every 100 grams of sugar added to soft drinks would raise the cost of a 375ml can of soft drink by just 16 cents, which is a small price signal that shows us that these drinks are bad for us, and that we should instead be choosing water -- the free and healthy alternative," Prof Robson said.

He said an AMA analysis projected such a tax would reduce consumption by 31 per cent by 2025-26, and was estimated to result in 16,000 fewer cases of type 2 diabetes, 4400 fewer cases of heart disease and 1100 fewer cases of stroke.

Prof Robson said the tax would result in government revenue of $2.8 billion across four years, which could be reinvested back into preventative health.

"We know it works, because more than 85 jurisdictions have already implemented taxes on sugary drinks."

Prof Robson said Australian sugar farmers had little to fear from such a tax as about 80 per cent of Australia's domestic sugar production was exported and only around five per cent went into sugary drinks.

"It is the right thing to do for the health of Australians. It's a no brainer."