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Study suggests that excess body weight causes 481,000 new cancer cases every year.

Overweight man

A new Lancet Oncology study led by Dr Melina Arnold from the International Agency for Research on Cancer (IARC), Global burden of cancer attributable to high body-mass index in 2012: a population-based study, estimates that excess body weight caused around 481,000 new adult cancers in 2012, which was 3.6% of all cancers worldwide. The burden is far higher in more developed countries, with almost two-thirds (64%) of these obesity-related cancers occurring in North America and Europe.

In a linked comment, also published today in The Lancet Oncology, NDPH Cancer Epidemiology Unit scientist Dr Benjamin Cairns suggests that global burden of cancer due to obesity needs to be taken in the context of other important causes of cancer, particularly smoking and infections, as well as other health problems related to obesity, such as vascular disease and diabetes.

Based on their results, Dr Arnold and colleagues 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 reveal 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% or 136,000 new cancers in 2012, and in women it was 5.4% or 345,000 new cases.

In developed (very high human development index; HDI) countries, around 8% of cancers in women and 3% in men were associated with excess bodyweight, compared with just 1.5% of cancers in women and about 0.3% of cancers in men in developing countries (low HDI).

According to Dr Arnold, “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.”

Writing in the linked Comment, Dr Cairns says, “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.” His full Comment appears in The Lancet Oncology.