If this statistic wasn't sobering enough, much of it is preventable.

A new report by the American Association for Cancer Research (AACR) has found that more than 50 per cent of all cancer diagnoses are down to lifestyle.

"Most notable among these causes are tobacco use, obesity, poor diet, lack of physical exercise, exposure to ultraviolet radiation either through the use of tanning devices or direct sun exposure, and failure to use or comply with interventions that treat or prevent infectious causes of cancer," the report says.

By simply "modifying personal behaviours" and making healthier choices, we can reduce and even eliminate many of the risks.

Kathy Chapman, director of the preventions program at the Cancer Council, believes such knowledge is empowering.

"People think of cancer as a death sentence and something we don't have control over," she says. "But there's good evidence to show there are a lot of things people can do."

In the AACR report, tobacco was the top preventable cause of cancer, responsible for 33 per cent of diagnoses.

In Australia, despite steadily dropping smoking rates, it is also the number one cause.

"There's lag factor," Ms Chapman says, explaining that we are seeing cancer cases now from people who started smoking 20 years ago.

"In NSW only around 15 per cent of people are smoking. Twenty years ago it was close to double that. But we need to get it below 10 per cent."

Barely a breath behind smoking, and accounting for 20 per cent of preventable causes in the AACR report, is individuals who are overweight or obese. With about two thirds of Australian adults either overweight or obese, it is an expanding problem for cancer here too.

"Obesity is also associated with inflammation, and cancer is a disease of inflammation," AACR spokesman and University of Pennsylvania cancer epidemiologist Timothy Rebbeck told The Atlantic news agency.

Poor diet and ultraviolet exposure were next in line.

Thankfully, as Ms Chapman points out, these are all aspects of our health that we can control.

But, she cautions that short-term extreme health kicks are not the key.

"Extreme diets and taking a lot of supplements is not where the evidence is," Ms Chapman says.

Rather, changes can be moderate but must be long-term to make a difference.

This applies to cancer survivors who aren't sticking to health improvements in remission.

Around two thirds are overweight or obese and only one in 10 eats the recommended five serves of veggies a day – much like the rest of Australians.

"I wouldn't say they're a healthier group than the rest of the population," Chapman says.

But they too could benefit from being healthier.

"Importantly, healthy approaches to living can also reduce cancer recurrence and improve outcomes following a cancer diagnosis," the AACR report states.

Ms Chapman says that the takeaway messages are that we can make a difference and that what we do most of the time and manage to maintain, makes the most difference.

She recommends quitting smoking (or, better yet, never starting), staying physically active with at least 30 minutes of exercise a day, eating plenty of fruits and vegetables and plant-based foods and only drinking alcohol in moderation.

All these things combined, she says, "put you in good stead for reducing the risk of cancer".