Half a million cancers a year fuelled by obesity

Obesity is to blame for nearly half a million cases of cancer a year, with overweight women at a far greater risk than men, according to a study by WHO's cancer research agency.
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 per cent or 136,000 new cancers in 2012, and in women it was 5.4 per cent 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 per cent of cancers in women and 3 per cent in men were associated with excess bodyweight, compared with just 1.5 per cent of cancers in women and about 0.3 per cent 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 per cent) of all new obesity-related cancers globally - and sub-Saharan Africa contributed the least (7,300 cancers or 1.5 per cent).
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 per cent of the country's new cancer cases in 2012), Jordan and Argentina (4.5 per cent), and in the UK and Malta (4.4 per cent).

In women, it was strikingly high in Barbados (12.7 per cent), followed by the Czech Republic (12 per cent) and Puerto Rico (11.6 per cent).
It was lowest in both sexes in countries within sub-Saharan Africa (less than 2 per cent in men and below 4 per cent 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.