Obesity and excess weight cause almost half a million new cancer cases each year worldwide - and almost two thirds occur in the developed countries of North America and Europe, a study has shown.
Cancers linked to obesity account for 3.6% of all those diagnosed globally, according to the research.
Scientists analysed data on cancer incidence and mortality from 184 countries and estimated the fraction associated with excess bodyweight in 2012.
They found that a quarter of the obesity-related cancers could be attributed to rising average body mass index (BMI) in the global population since 1982 and were “realistically avoidable”.
North America contributed by far the largest number of cases – 111,000 cancers – making up almost a quarter of all new cancers linked to excess weight.
“Our findings add support for a global effort to address the rising trends in obesity”
Dr Melina Arnold
Within Europe, the burden was largest in countries of the former Soviet Union. Eastern bloc countries accounted for more than a third of all the European cases, a total of 66,000 cancers.
Lead researcher Dr Melina Arnold, from the International Agency for Research on Cancer (IARC) in Lyon, France, said: “Our findings add support for a global effort to address the rising trends in obesity.
“The global prevalence of obesity 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.”
The results, published in The Lancet Oncology journal, showed that obesity-related cancer was a greater problem for women than men - chiefly due to womb and breast cancer.
“If this trend continues it will certainly boost the future burden of cancer, particularly in South America and North Africa”
Excess weight was responsible for 5.4% or 345,000 new cancers in women in 2012 and 1.9% or 136,000 in men.
Post-menopausal breast, womb and bowel cancers accounted for almost three quarters of obesity-related cancers in women.
In men, bowel and kidney cancers made up the majority of excess weight-associated cancers.
The region of the world with the lowest rates of obesity-related cancer was sub-Saharan Africa, where these cases made up 1.5% of the total.
Writing in a linked comment in the journal, Dr Benjamin Cairns from Oxford University said: “If 3.6% 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.
“Global health resources specifically for cancer prevention are not so large, and the 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.”
“The resources targeted at obesity must be balanced against those for other important causes of cancer”
Dr Kate Allen, executive director of science and public affairs at World Cancer Research Fund International, which funded the research, said: “These worrying results highlight that it’s crucial to maintain a healthy weight to prevent so many common cancers.
“In the United Kingdom, 13,000 cases diagnosed in 2012 in women (8.2% of all cancers) could be ascribed to overweight and obesity,” she said. “It’s also alarming to see that men in the UK are fourth in the world in this obesity cancer league table, with 6,000 cases (4.4% of all cancers) attributed to being overweight or obese.
“Cancer is an epidemic problem, and to tackle it we need to help people take measures to be a healthy weight,” she added.