In men, being overweight was blamed for 136,000 new cases, and in women, 345,000 cancer diagnoses, most of them of the colon, kidney and breast.

Being overweight is now causing nearly half a million new cancer cases in adults every year, roughly 3.6 per cent of the world's total, a study says.

A quarter of these cases are "realistically avoidable", said the authors of the work published in The Lancet Oncology on Wednesday.

Led by scientists at the International Agency for Research on Cancer, the paper drew on a range of sources, including a large database of cancer incidence and mortality for 184 countries in 2012.

In men, being overweight was blamed for 136,000 new cases, more than two-thirds of them cancers of the colon and kidney.

In women, it was linked to 345,000 cancer diagnoses, nearly three-quarters of which were post-menopausal breast, endometrial and colon cancers.

Mirroring the spread of obesity in developed countries, the tally was highest in North America, which accounted for nearly a quarter of all the weight-related new cancer cases.

Sub-Saharan Africa had the fewest, with 7,300 cases.

"Our findings add support for a global effort to address the rising trends in obesity," said lead researcher Melina Arnold.

"The global prevalence in adults has doubled since 1980. If this trend continues, it will certainly boost the future burden of cancer, particularly in South America and North Africa, where the largest increases in the rate of obesity have been seen over the last 30 years."

Measured as a ratio of weight in kilograms-to-height in metres squared, a body mass index (BMI) of 25 to 29.9 is considered overweight, and 30 plus as obese.

Elsewhere in The Lancet, an updated map of cancer survival shed light on a persisting gulf between rich and poor countries, as well as within advanced economies themselves.

The CONCORD-2 study looked at a key benchmark - the rate for survival five years after diagnosis - among 25.7 million patients who had had one of 10 common cancers.

For acute lymphoblastic leukaemia in children - the most common childhood cancer - the rate ranged from 90 per cent in Canada, Austria, Belgium, Germany and Norway, to just 16-50 per cent in Jordan, Lesotho, central Tunisia, Jakarta and Mongolia.

In most developed countries as well as in Brazil, Colombia and Ecuador, the five-year survival from breast and colorectal cancers has increased, thanks to earlier diagnosis and better treatment.