We’ve known for some time now that obesity was running neck and neck with tobacco as a leading preventable cancer cause. Unfortunately, a recent study done by the International Agency for Research on Cancer has revealed that the situation is getting much worse. In 2012, as many as 500,000 cancers worldwide were directly linked to obesity, which means that in reality half a million cases of cancer were completely avoidable.

The study used data from 182 different countries around the world and used the GLOBOCAN database of cancer incidence. The researchers found that no matter where they looked, obesity remained a significant cause of cancer for patients. However, although the problem was clearly global, it was noted that North America contributed the most new cases “by far” and sub-Saharan Africa the least. There were also noteworthy gender differences in the occurrence of obesity-related cancers. It was found that extra weight could be attributed to 136,000 new cancer cases for men and 345,000 for women.

"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," concluded Dr. Melina Arnold, the lead researcher on the study, in a press release.

The most common obesity-related cancers in women are post-menopausal breast, endometrial, and colon cancers, while colon and kidney cancers accounted for the most obesity-related cancers in males. A previous CNN report predicted that extra weight "could account for 14 percent of all death from cancer in men and 20 percent of those in women."

Doctors are not exactly sure why extra weight so often causes cancer, but it may be because obesity causes the body to work differently. This abnormal functioning may then lead to harmful cell growth and cell division.

For example, Dr. Clifford Hudis, an oncologist at Memorial Sloan Kettering, explained to CNN that in the case of breast cancer, obesity can cause chronic inflammation that may lead to an increase in the production of estrogen. Estrogen has been identified as a leading factor in the development of breast cancer tumors.

While the staggering numbers of preventable new cases of cancer are overwhelming, it’s not to be forgotten that, according the study, these cases are "realistically avoidable." Losing weight will reduce, if not eliminate, one's risk for developing cancers of this type, as well as improve an individual’s overall quality of life.

Source: Arnold M, Pandeya N, Brynes G, et al. Global burden of cancer attributable to high body-mass index in 2012: a population-based study. The Lancet. 2014.