Credit: Fejnation (Flickr)

Australia has been warned by a leading international cancer expert that it is on a cancer collision course, with a great increase in cancer cases predicted within the next 20 years unless action is taken to curb the obesity epidemic.

Negative lifestyle that includes smoking and drinking excessive alcohol with poor diet and lack of exercise are all factors which are set to double within the next two decades.

Professor Graham Colditz, an Australian cancer prevention expert based in the US said obesity and overweight combined cost the country nearly $21 billion per year, a figure that could increase if no actions are taken today.

Australia's increasingly older population in the next 25 years will result in double the number of cancer cases being diagnosed, said Prof Colditz, who is visiting NSW to assist the Cancer Council in promoting cancer prevention.

When you include the additional consequences of obesity, we could see a major spike to the number of cancer cases, diabetes and other life threatening diseases, placing immense strain on the wellbeing of Australians and the health system.

But the future is not written in stone. Up to half of all cancers are preventable though simple lifestyle changes such as quitting smoking, exercising and eating healthily, said Prof Colditz.

Obesity is a serious problem, said the director of health strategies, Kathy Chapman, at Cancer Council NSW.

One in four Australian children is already obese or overweight, she said.

We cannot allow this epidemic to worsen.

Our message is that you don't have to make massive lifestyle changes to reduce your risk of developing cancer.

Even small things, like getting off the bus a stop early and walking the rest of the way, can result in big benefits to your health.

Cancer Council NSW is currently conducting research projects to help families eat more fruits and vegetables, and understand the long-term benefits of exercise and healthy diet.

Please visit or call the Cancer Council Helpline at 13 11 20 for more details regarding cancer prevention.