Extra Weight Tied to 500k Cancer Cases Each Year

Cancer cases tied to being overweight were more common in more developed countries with higher numbers of overweight patients than in developing countries

(RxWiki News) People who think the extra pounds they carry around can't hurt them may want to think again. Being overweight may raise the risk for cancer, a new study suggests.

This new study found that nearly half a million cases of cancer each year could be a result of patients being too heavy.

Developed countries had the most overweight people and the highest cancer rates. Controlling weight may be a way to avoid certain cancers, the authors of this study suggested.

Close to half a million new cancers in 2012 were linked to having a body mass index (BMI) of at least 25, these researchers found. Edward Giovannucci, MD, ScD, professor of nutrition and epidemiology at the Harvard School of Public Health in Boston, told dailyRx News that even high numbers like this may be underselling the issue.

“The estimates of attributable cancers to [fat] are underestimated," he said. "This is especially true in older persons, who have a loss of [muscle], which complicates the meaning of body mass index."

BMI is a measure of body fat based on weight and height. A BMI of 25 to 29.9 is considered overweight. Anything above 30 is considered obese.

Melina Arnold, PhD, of the International Agency for Research on Cancer in Lyon, France, and colleagues wrote the current study.

Dr. Arnold and team drew the data for the study from a number of sources, including GLOBOCAN, a database of cancer cases and deaths for 184 countries. They looked at how heavy people were in 1982 and the incidence of cancer at least 10 years later (giving time for cancer to occur). They then looked at the same issues in 2012 because more people in 2012 were overweight than in 1982.

The study authors found that about 3.6 percent of all new cancers in adults aged 30 and older could be tied to high BMI. That translates to about 481,000 new cancer cases each year that might have been caused by high BMI.

The relationship between being overweight and developing cancer appeared strongest in women. In men, excess weight was thought responsible for 1.9 percent (or 136,000) of new cancers in 2012, according to Dr. Arnold and colleagues. In women, high BMI was responsible for 5.4 percent (345,000) new cases, these researchers said.

Most of the cases in heavy women (72.5 percent) were breast cancer occurring after menopause, uterine cancer and colon cancer. Sixty-six percent of the cancers among heavier men were kidney or colon cancers.

Cancer among people with a BMI of at least 25 was found to be far more common in more developed countries, with almost two-thirds (64 percent) of these weight-related cancers occurring in North America and Europe, Dr. Arnold and team said. That doesn't mean other areas are immune to weight gain and related cancers — these researchers noted that more people were rapidly gaining weight in regions like Latin America and North Africa.

Dr. Giovannucci said heavier people aren't just more inclined to develop cancer, but they are also more likely to die from that cancer than people with lower BMIs.

Dr. Arnold and team stressed the need for more programs to assist with weight loss. There is a “need for research into effective interventions to control weight gain to avoid further increases in the burden of cancer related to high BMI,” they wrote.

In an editorial about this study, Benjamin J. Cairns, PhD, of the Nuffield Department of Population Health in Oxford, UK, noted that cancer has many more causes that just being overweight. He said global public health money would be better spent on preventing cancer causes other than being overweight.

“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," Dr. Cairns wrote.

The study and editorial were published Nov. 25 in The Lancet Oncology.

The World Cancer Research Fund funded this study. The authors disclosed no conflicts of interest.

Review Date: 
November 25, 2014