In a new study, scientists have discovered that obesity leads to around 481 000 new cancer cases every year in adults, or 3.6 percent of cancers worldwide.

The burden is far higher in more developed countries, with almost two-thirds (64 percent) of these obesity-related cancers occurring in North America and Europe.

Based on the results, the 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 reveal that obesity-related cancer creates 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 (low HDI).

Dr Arnold said that their 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 the trend continued, it would boost the future burden of cancer, particularly in South America and North Africa.

The findings are published in The Lancet Oncology.