What if you were told there was something within your control you could do to significantly reduce your lifetime chances of developing cancer? There is, and it’s pretty basic: maintain a healthy weight.
The alarm was first raised by the American Cancer Society about the link between obesity and an increased risk of cancer more than a decade ago, in 2003. Now, that link has been further verified by a new study from the United Kingdom; the results show the likelihood for obese women to develop certain types of cancer is 41 percent greater than for women of a healthy weight.
The study comes from Cancer Research UK, an organization that supports research into all types of cancer, with a focus on understanding its biology. To determine the increased risk, investigators assessed data on the lifetime cancer risk in the UK population, data on obesity among UK women, and the results of a 2011 study published in the British Journal of Cancer.
Dr. Noor Merchant, a board-certified medical oncologist with offices in Vero Beach and Sebastian, says the link between breast and endometrial cancers and obesity is strong, and that there is also evidence that obesity is a risk factor for colon cancer.
Dr. Merchant is active in clinical research and has presented his findings to scientific organizations such as the American Association of Cancer Research and the American Society of Clinical Oncology. He spoke of a recent study from Johns Hopkins which estimated that two-thirds of cancers can be attributed to the random mutations that occur in stem cell divisions over the course of a person’s lifetime, while the other third is associated with inherited genetics or environmental factors such as obesity.
Obesity is commonly defined as having a Body Mass Index (BMI) of 30 or more. There are a number of ways to measure BMI; one of the simplest, called a skin fold assessment, uses special calipers to measure the thickness of skin folds for up seven parts of the body. Many gyms have the calipers and specially-trained technicians to do the measurements; in Vero Beach, Christi’s Fitness at 1250 Old Dixie Highway provides that service.
Nearly 80 million U.S. adults are considered obese, about a third of the population. There are biological reasons for the link between obesity and cancer:
• Fat tissue produces excess amounts of estrogen; in turn, high levels of estrogen have been associated with certain cancers.
• An increased level of insulin and insulin-like growth factor (IGF-1) is more common in people with obesity; this may promote the development of certain types of tumors.
• Fat cells produce hormones called adipokines which may stimulate or inhibit cell growth.
• People with obesity often have chronic, unresolved inflammation, which has been associated with increased cancer risk.
A 2014 study, published in the UK medical journal The Lancet, monitored more than 5 million men and women for an average period of 7.5 years. All were cancer-free at the start of the assessment; over time, about 170,000 developed one of the 22 cancers that account for 90 percent of all diagnosed cancers in the UK. BMI was linked to the development of 17 of the 22 cancers. The link was particularly strong for certain cancer types, including gallbladder, kidney, liver, cervical, thyroid, colon, ovarian, breast and leukemia. Another recent study, conducted by UCLA in 2013, was the first to find a direct link between obesity and cancer of the pancreas.
Obesity is not only linked to an increased risk in developing cancer, it can also result in poorer cancer outcomes – an increased risk of recurrence, faster and increased disease progression, and higher mortality rates. One reason is that obese people have poorer cancer outcomes is that they often have another weight-related condition, such as diabetes or heart disease, which affects their overall health and survival odds. Obese patients are also more at risk for experiencing surgical complications, including infection.
Obese patients also have an increased chance of developing blood clots during chemotherapy. On a related note, the thinking on chemotherapy dosing may be changing. Doses are typically based on the patient’s weight, but in the past oncologists would often cap the chemo at a certain dose for their obese patients, regardless of their weight. This, of course, was out of concern that a larger dose may be too toxic. Studies have shown that doses based on weight, even for obese patients, do not result in more side effects than those experienced by patients of a healthy weight. This is something for patients to be aware of and talk to their oncologist about if chemotherapy is the agreed-to treatment plan.
Dr. Merchant says that consistent, moderate exercise is particularly important after treatment for breast cancer. He recommends exercising 5 days a week, 30 minutes at a time. “It improves survival rates and reduces the risk of recurrence,” he says.
Dr. Merchant’s Sebastian office is located at 13060 Highway A1A, Suite A; his Vero Beach office is at 1880 37th Street, Suite 1. Either office can be reached at 772-589-0879.