Almost one third of all cancers diagnosed in Australia could have been prevented, new research has found.
The Cancer Council-commissioned research found an estimated 37,000 cancer cases in 2010 were caused by factors such as smoking, UV exposure, alcohol and obesity. 
The study, published in The Australian and New Zealand Journal of Public Health, estimated that 33 per cent of all cancers in men and 31 per cent of those in women were avoidable.
Lead researcher David Whiteman said the results showed Australia had a large burden of preventable cancers.
"When we have more knowledge and more data in the future, I expect the proportion of preventable cancers will be even higher," he said.
Professor Whiteman, of the Brisbane-based QIMR Berghofer Medical Research Institute, said obesity's role as a cancer risk factor was becoming better understood.
"When we redo this analysis in five-10 years I'm confident there will be more cancers known to be caused by obesity," he said. "The research is still being done now so the risks associated with obesity will be estimated more precisely." 
He said obese women produced more oestrogen, which could lead to higher breast cancer risks. In obese people of both sexes tissue inflammation could result in cells becoming cancerous in certain organs.
The research linked 3917 cancer cases to obesity, including one in five kidney cancers, one in 10 colon cancers and 8 per cent of all post-menopausal breast cancers. An additional 7000 cases were linked to a poor diet. 
The researchers estimated the number of preventable cancer cases based on the proportion of the population that met each risk criteria. The calculations also took into account differing levels of risk (such as cigarettes smoked per day) or multiple factors, Professor Whiteman said.
Smoking was linked to 15,525 cancer cases, including four out of five lung cancers, three out of five throat and oesophageal cancers, and one in five stomach, liver and kidney cancers.
Cancer Council Australia chief executive Sanchia Aranda said the research should encourage Australians to be positive about minimising their risk of being diagnosed with preventable cancers.
"It's time to bust the myth that everything gives you cancer and do more to reduce the risks that we know cause cancer," Professor Aranda said.
She said people were confused by fad diets and conflicting health advice, but that a diet rich in vegetables, fruit and whole grains helps to cut cancer risk.
According to Australian Institute of Health and Welfare data, two out of three Australian adults and one in four children are overweight or obese.
ACT Heart Foundation chief executive Tony Stubbs said small changes to lifestyle and eating habits could make a big difference.
"Smoking is one of the key things that threaten heart disease and cancer so people who smoke should be seeking assistance to quit, although there are other factors such as being physically inactive and overweight," he said.
"We need to make sure we have 30 minutes of physical activity a day and are getting two services of fruit and five serves of vegetables, while also reducing the amount of processed food and drink we consume." 
 - with Henry Belot