Excess body weight is responsible for nearly half a million new adult cancer cases every year, equating to around 3.6% of cancers around the globe, suggests new research published today in The Lancet Oncology.

Scientists from the International Agency for Research on Cancer (IARC) estimate that a quarter of all obesity-related cancers in 2012 (118,000 cases) can be put down to the population’s growing body mass index (BMI) since 1982, and could therefore potentially have been avoided.

The findings revealed a higher proportion of obesity-related cancers in developed countries; North America was top of the global tally accounting for 23%, while at the other end of the scale sub-Saharan Africa contributed just 1.5%.

Also, the burden was found to be higher in women than men, causing 5.4% and 1.9% of new cancer cases in each sex, respectively, and there was significant variation between countries. In men, the highest levels were seen in the Czech Republic (5.5% of the country’s new cancer cases), Jordan and Argentina (4.5%), and in the UK and Malta (4.4%), while in women Barbados (with 12.7%) topped the list, followed by the Czech Republic (12%) and Puerto Rico (11.6%).

Research lead Melina Arnold told The Lancet Oncology that the findings “add support for a global effort to address the rising trends in obesity,” the global prevalence of which has doubled in adults since 1980. But Benjamin Cairns, from the University of Oxford, also noted that “resources targeted at obesity must be balanced against those for other important causes of cancer, particularly infections and tobacco use, which are each associated with much larger proportions of cases”.

Also commenting on the report, Eluned Hughes, Senior Manager, Information at Breakthrough Breast Cancer, said it “reinforces what we already know, that we need to do so much more to reverse the tide of increasing obesity levels”, and pointed out that just 30 minutes of exercise a day can reduce the risk of developing breast cancer by 20%.