Cancers linked to unhealthy lifestyles are "one of the biggest challenges facing the world", an expert said today.
The rise in cancer linked to poor diet and a lack of exercise poses as much of a problem in the 21st-century as providing access to clean water did in the 19th-century, he said.
And Professor Martin Wiseman, medical and scientific adviser for the World Cancer Research Fund (WCRF), warned that millions of people around the world face an early death from the disease.
While the increase in many cancers is linked to the fact people are living longer, tens of thousands of cases could be prevented every year if people ate better, kept to a healthy weight and exercised.
Around one in three of the most common cancers in high-income countries, and about one in four in medium and low- income countries could be stopped if people led healthier lives, estimates suggest.
According to the United Nations, the number of deaths from cancer worldwide is set to double by 2030.
And global cases of cancer have risen dramatically in the last 30 years, from 6.3 million cases in 1980 to 8.1 million in 1990 and 11.3 million in 2007.
But Prof Wiseman said this doubling was not inevitable, and more should be done to prevent lifestyle cancers. He was speaking ahead of the WCRF's international scientific conference in London, which will hear from speakers from the World Health Organisation and the International Agency for Research on Cancer.
"It is clear that the rising number of lifestyle-related cancers is one of the biggest challenges facing the world today," he said. "It is important we do not underestimate it."
It's estimated a quarter of all cancer deaths are caused by unhealthy living and obesity.
Cancers particularly affected by lifestyle include those of the bowel, stomach, mouth, foodpipe and breast.