Sugar-sweetened drinks should be taxed and obesity renamed a chronic disease, according to a coalition of Australia's most influential doctors' groups.

The Committee of Presidents of Medical Colleges, representing bodies including the Royal Australian College of GPs, the Royal Australasian College of Physicians and the Royal Australasian College of Surgeons, has developed a six-point obesity action plan to tackle what it calls the most pressing public health issue.

Professor Nick Talley, head of the Committee of the Presidents of Medical Colleges, said urgent definitive action was needed.

"We need leadership, not just telling people to lose weight," he said.

"With smoking and tobacco control, we took risks and it had a dramatic effect."

He said obesity was a "real disease, not simply a lifestyle choice".

The group's six point plan includes:

Reclassifying obesity as a chronic disease

Reclassifying obesity as a chronic disease Introducing a tax on sugar-sweetened beverages

Introducing a tax on sugar-sweetened beverages Advocating for better options for treating obesity including more cost effective medications and better access to bariatric surgery

Advocating for better options for treating obesity including more cost effective medications and better access to bariatric surgery Targeted training for all medical and health professionals to ensure a focus on nutrition, physical activity and obesity prevention and management

Targeted training for all medical and health professionals to ensure a focus on nutrition, physical activity and obesity prevention and management Lead by example in encouraging healthy food choices

Lead by example in encouraging healthy food choices Expand prenatal and early childhood obesity prevention strategies

Medical groups said they would lead by example by encouraging medical colleges, hospitals, universities and health services to offer healthier food choices to staff and limiting access to sugar-sweetened beverages.

Royal Australian College of GPs president Dr Bastian Seidel said the medical profession needed to lead the way on healthy eating.

"We need to live by the advice that we are giving to our patients," he said.

Sugary drink tax can save lives: UN health agency

The World Health Organisation has urged countries to tax sugary drinks, saying it can lower consumption of sugars, reduce obesity and tooth decay.

Dr Douglas Bettcher, who heads WHO's department for preventing non-communicable diseases, said if governments taxed products like sugary drinks, they could reduce suffering and save lives.

Sydney obesity physician Dr Georgia Rigas said many doctors felt they were failing overweight and obese patients, as it was difficult to get access to effective treatments.

"There are three medications approved for obesity, but none are on the Pharmaceutical Benefits Scheme. Why is that?" she said.

She said only 12 per cent of weight loss surgery was carried out in public hospitals in Australia.

"We are falling short because for some patients, diet and lifestyle measures alone are not effective," she said.

The health groups also vowed to endorse the national obesity prevention strategy, which includes encouraging physical activity, better access to fresh foods and including obesity prevention in environmental planning.

'We can make a difference': medical experts

Obesity is fast becoming Australia's biggest health challenge.

In 2014-15, an estimated 11.2 million adults or around two thirds of the population were overweight or obese.

One million or one in four children aged five to 17 were overweight or obese.

Professor Andrew Wilson, director of the Menzies Centre for Health Policy at the University of Sydney, said Australia could act to slow obesity rates.

"It is critical that we do something to overcome the inaction on obesity," he said.

He said regulatory action, tax measures and education were the key elements to successfully tackling challenges such as obesity.

The Australia Medical Association supports many of the measures outlined by the coalition of health groups.

The Committee of Presidents of Medical Colleges will urge Prime Minister Malcolm Turnbull and Health Minister Sussan Ley to adopt the plan.

Sugar tax 'discriminatory': soft drink manufacturers

Soft drink manufacturers rejected the calls for a tax on sugar-sweetened beverages.

Australian Beverages Council chief executive Geoff Parker called it "a discriminatory tax that evidence clearly shows will not improve public health whatsoever".

He cited a report from the McKinsey Global Institute, which classified taxation as one of the least effective obesity interventions.

"Obesity is a serious and complex public issue with no single cause or quick-fix solution," Mr Parker said.

"A new tax is not the way to make our nation healthier."