Obesity is associated with close to 500,000 new cancer cases worldwide each year, and nearly two-thirds of obesity-related cancers occur in North America and Europe, a new report shows.
The analysis of data from 184 countries showed that excess weight was associated with 345,000 (5.4 percent) of new cancers in women in 2012, and 136,000 (1.9 percent) of new cancers in men in 2012.
Among women, postmenopausal breast, endometrial and colon cancers accounted for nearly three-quarters (250,000 cases) of obesity-related cancers, while colon and kidney cancers accounted for more than two-thirds (nearly 90,000 cases) of obesity-related cancers in men.
Excess weight was associated with about 8 percent of cancers in women and 3 percent of cancers in men in developed nations, compared with 1.5 percent of cancers in women and 0.3 percent of cancers in men in developing nations.
In 2012, the highest number of obesity-related cancers was in North America, with more than 110,000 (23 percent of the worldwide total), while the lowest number was in sub-Saharan Africa, with 7,300 cases (1.5 percent of the global total). In Europe, there were 66,000 obesity-related cancer cases.
Rates of obesity-related cancers varied widely among countries. Among men, rates were particularly high in the Czech Republic (5.5 percent of new cancer cases in 2012), Jordan and Argentina (4.5 percent), and the U.K. and Malta (4.4 percent). Among women, rates were highest in Barbados (12.7 percent), Czech Republic (12 percent), and Puerto Rico (11.6 percent).
Rates were lowest in the countries of sub-Saharan Africa, with less than 2 percent in men and less than 4 percent in women, according to the study published Nov. 25 in The Lancet Oncology.
"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," study leader Dr. Melina Arnold, of the International Agency for Research on Cancer, said in a journal news release.
"If 3.6 percent of all cancers are associated with [overweight and obesity], 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 U.K., wrote in an accompanying editorial.
"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," he said.
While the study showed an association between obesity and the rising number of cancer cases worldwide, it did not prove a cause-and-effect link.