Nearly half a million new cancer cases per year can be attributed to high body mass index, according to a new analysis conducted by researchers from the International Agency for Research on Cancer and published in The Lancet Oncology.
The new analysis - which looked at data from 2012 - finds that 3.6% of the total global cancer burden is linked with high BMI, and that cancer due to overweight and obesity is far more common in developed countries than in less developed countries.
"Overall, we see that while the number of cancer cases associated with overweight and obesity remains highest in richer countries, similar effects are already visible in parts of the developing world," explains co-lead author Dr. Isabelle Soerjomataram.
The most affected area remains North America, where an estimated 111,000 new obesity-related cancer cases emerged in 2012 - around 23% of the total global BMI-related cancer burden.
Europe also has a large cancer burden linked with overweight and obesity, with Eastern Europe accounting for 6.5% (65,000 cases) of all new European cancer cases.
The proportion of cancers associated with overweight and obesity in Asian countries is not as large, but due to population size, the authors note that "it still translates into a considerable absolute number of cases."
For instance, although only 1.6% of China's new cancer cases were found to be attributable to overweight and obesity, this still comprised 50,000 cancer cases in total.
The researchers compare this prevalence to the rates in Africa, where 1.5% of all new cancer cases were related to overweight and obesity, but the total number of cases in the entire continent was just 7,300 during 2012.
Analysis finds significant gender differences of BMI-related cancer cases
In the analysis, incidence of BMI-related cancer varied across countries according to gender.
The countries with highest cancer burden attributable to overweight and obesity in men were:
- Czech Republic (5.5% of the country's new cancer cases)
- Jordan (4.5%)
- UK (4.4%)
- Malta (4.4%).
For women, the countries with the highest cancer burden attributable to overweight and obesity were:
- Barbados (12.7% of the country's new cancer cases)
- Czech Republic (12.0%)
- Puerto Rico (11.6%).
The proportion of cancers related to obesity was found to be significantly higher in women than in men.
The population-attributable proportion of BMI-linked cancers in new cancer cases among women was 5.3%, compared with just 1.9% among men.
"Women are disproportionately affected by obesity-related cancers," says Dr. Melina Arnold, one of the study's lead authors. "For example, for postmenopausal breast cancer, the most common cancer in women worldwide, the study suggests that 10% of these cancers could have been prevented by having a healthy body weight."
Endometrium, colon and breast cancers accounted for 73% of the cancers linked to high BMI in women. Kidney and colon cancers accounted for 66% of all cancers associated with high BMI in men.
Dr. Christopher Wild, director of the International Agency for Research on Cancer, comments on the study's findings:
"The number of cancers linked to obesity and overweight is expected to rise globally along with economic development.
This study stresses the importance of putting in place efficient weight control measures, to curb the high number of cancers associated with excess body weight and to avoid the problems faced by rich countries being repeated in those now undergoing rapid development."