Weighing the evidence: does obesity cause cancer?
Weighing the evidence: does obesity cause cancer?
Updated: SEPTEMBER 19, 2016 — 8:54 AM EDT
A woman walks along the boardwalk while leaving the U.S. Open tennis tournament in New York in this September 4, 2007 file photo. REUTERS/Lucas Jackson/Files
by Richard Schilsky, MD
More than five decades ago, the U.S. Surgeon General issued a history-changing report linking tobacco use to cancer. By the time I became an oncologist in the 1970s, the number of Americans who smoked had dropped significantly—a trend that continues today.
A woman walks along the boardwalk while leaving the U.S. Open tennis tournament in New York in this September 4, 2007 file photo. REUTERS/Lucas Jackson/Files Slideshow icon SLIDESHOW
Weighing the evidence: does obesity cause cancer?
Most everyone is aware that obesity has long been linked to an increase in the risk of diabetes, heart disease and stroke. But now, we’re seeing growing evidence that links obesity to a higher risk of cancer too, including a study published last month in The New England Journal of Medicine reporting that being overweight or obese increases a person’s risk for developing at least 13 different types of cancer, including breast, prostate, and colorectal cancers.
With more than two-thirds of American adults now overweight or obese, this is, understandably, both a cause for concern and a call to take action.
Even though the data in this study add to a large body of literature suggesting that being overweight or obese increases cancer risk, we still can’t say for sure that an individual person’s cancer was caused by obesity because it is likely that multiple factors contribute to the development of cancer, including genetic risk, family history, environmental exposures and other aspects of each person’s lifestyle.
And, we still don’t fully understand the mechanisms by which obesity might trigger cancer. People who are overweight or obese often have increased levels of insulin and estrogen that promote the development of certain cancers. Other research has shown that certain kinds of fat cells may promote tumor development by causing inflammation.
Obesity not only increases a person’s chance of developing certain cancers, but being obese greatly complicates the care of people who are diagnosed with cancer. Imaging tests that are used to look for cancer are often less effective in obese patients. Obesity can increase the risk of complications during and after major surgery. Patients who are overweight or obese are more likely to receive an under-dose of chemotherapy, which might reduce the effectiveness of cancer treatment. For some cancers, obesity is associated with a worse prognosis after diagnosis, as well as an increased risk of cancer recurrence.
I think we all intuitively know that being overweight or obese is not good for us, and that we should work toward achieving optimal weight for the best quality of life. We also know that this is not an easy proposition. Losing weight often requires a person to change longstanding behaviors, as well as grapple with cultural, financial, and physical challenges. We’re also not sure that losing weight reduces an obese person’s risk of developing cancer but given the many other health benefits of maintaining a normal weight, it’s certainly worth a try.
What You Can Do
If you or a family member has cancer and are wondering how your weight and other health factors might impact your medical care, I encourage you to talk with your healthcare team. The following questions can be a starting point:
How will my weight affect my treatment options and my ability to tolerate the recommended treatment?
Can you refer me to a registered dietician or weight-loss program to help me find the best method for losing weight?
What is the best kind of exercise program for me to follow while receiving treatment?
Are there specific exercises or foods that you recommend I avoid while I’m receiving treatment?
Should I consider medication or surgery to lose weight?
Dr. Richard Schilsky is a medical oncologist and the Chief Medical Officer of the American Society of Clinical Oncology. For more information on ASCO see