Researchers led by Dr Melina Arnold from the International Agency for Research on Cancer (IARC), estimate that a quarter of all obesity-related cancers in 2012 (118,000 cases) were attributable to the rising average body mass index (BMI) in the population since 1982, and were therefore 'realistically avoidable.'
Using data from a number of sources including the GLOBOCAN database of cancer incidence and mortality for 184 countries, Arnold and colleagues created a model to estimate the fraction of cancers associated with excess bodyweight in countries and regions worldwide in 2012, and the proportion that could be attributed to increasing BMI since 1982.
The findings show that obesity-related cancer is a greater problem for women than men, largely due to endometrial (womb/uterus) and post-menopausal breast cancers.
In men, excess weight was responsible for 1.9 percent or 136,000 new cancers in 2012, and in women it was 5.4 percent or 345,000 new cases.
Post-menopausal breast, endometrial, and colon cancers were responsible for almost three-quarters of the obesity-related cancer burden in women (almost 250,000 cases), while in men colon and kidney cancers accounted for over two-thirds of all obesity-related cancers (nearly 90,000 cases).
In developed countries, around 8 percent of cancers in women and 3 percent in men were associated with excess bodyweight, compared with just 1.5 percent of cancers in women and about 0.3 percent of cancers in men in developing countries.
North America contributed by far the most cases with 111,000 cancers - equivalent to almost a quarter (23 percent) of all new obesity-related cancers globally - and sub-Saharan Africa contributed the least (7,300 cancers or 1.5 percent).
Within Europe, the burden was largest in eastern Europe, accounting for over a third of the total European cases due to excess BMI (66,000 cancers).
The proportion of obesity-related cancers varied widely between countries. In men, it was particularly high in the Czech Republic (5.5 percent of the country's new cancer cases in 2012), Jordan and Argentina (4.5 percent), and in the UK and Malta (4.4 percent).
In women, it was strikingly high in Barbados (12.7 percent), followed by the Czech Republic (12 percent) and Puerto Rico (11.6 percent).
It was lowest in both sexes in countries within sub-Saharan Africa (less than 2 percent in men and below 4 percent in women).
"If 3.6 per cent of all cancers are associated with high BMI, that is nearly half a million cancers, but this number is large mainly because the world population is large," Dr Benjamin Cairns from the University of Oxford in the UK said.     

The study was published in the journal The Lancet Oncology.

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