Obesity Raises Cancer Risk

For colon cancer, the associations were stronger in men than in women (24 percent vs. 9 percent).

There were stronger associations in Asia-Pacific populations between greater BMI and both premenopausal and postmenopausal breast cancers.

Although the main message is still to maintain a healthy weight, this research might indicate earlier screening for certain cancers, said Dr. Greg Cooper, interim chief of the gastroenterology division at Ireland Cancer Center of University Hospitals and Case Comprehensive Cancer Center in Cleveland. "If someone is obese, then lower the threshold for screening," he said. "One of the cancers they identified is esophageal adenocarcinoma, which is not as common as colon cancer, but it is increasing in incidence. It is thought to be related to reflux, so as a gastroenterologist, if I have a patient who has reflux and is obese, I might lower the threshold for doing an endoscopy. For other cancers like colon cancer, those guidelines are pretty well-established, and this probably wouldn't change practice."

Experts aren't sure why extra fat can lead to malignancies, but changes in the circulating levels of various hormones (insulin, insulin-like growth factors and sex steroids) might explain the link.

Here's more bad news as the world heads for a smoke-free future: An accompanying commentary from Swedish researchers notes that as people quit smoking (the biggest cause of cancer in developed countries), weight gain may become the main lifestyle factor contributing to new cancers.

More information

Visit the American Cancer Society for more on the different types of cancer.

SOURCES: Michael J. Thun, M.D., head, epidemiological research, American Cancer Society, Atlanta; Greg Cooper, M.D., professor, medicine, and interim chief, gastroenterology division, Ireland Cancer Center of University Hospitals and Case Comprehensive Cancer Center, Cleveland; Feb. 16, 2008,The Lancet