When it comes to reducing your risk of cancer, maintaining a healthy weight may be as important as avoiding tobacco and overexposure from the sun. In fact, the American Cancer Society (ACS) has found that those who follow a healthy lifestyle, by eating a nutritious diet, limiting alcohol consumption and taking other important steps, are 10 to 20 percent less likely to be diagnosed with cancer.
Those are important numbers when you consider that roughly 70 percent of adults in America are either overweight (defined as having a body mass index, or BMI, of 25 to 29.9) or obese (with a BMI of 30 or more). First recognized as a disease by the American Medical Association in 2013, obesity is expected to soon overtake tobacco as the leading preventable cause of cancer, according to the American Society of Clinical Oncology (ASCO).
Obesity has been linked to 13 types of cancer—uterine, esophageal, liver, stomach, kidney, brain, multiple myeloma, pancreas, colorectal, gallbladder, ovarian, breast and thyroid—but only a little more than half of Americans are aware that it’s a risk factor for cancer. Carolyn Lammersfeld, Vice President of Integrative Medicine at Cancer Treatment Centers of America® (CTCA), says that many patients are open to learning more about the connection between obesity, cancer risk and outcomes. “My experience is that many people with cancer are aware they’re carrying extra body weight and want to do something about it, but a lot of them don’t know there’s a connection between cancer and being overweight, including cancer outcomes,” she says.
What causes obesity’s cancer connection?
According to the National Cancer Institute (NCI), there are several possible reasons, including chronic inflammation, which may be present in people with obesity. An increase in insulin and other hormones such as estrogen may also increase cell division or trigger a growth in cancer cells. Many studies, in fact, have suggested that obese women may have an increased risk of postmenopausal breast cancer, likely because of increases in estrogen. In postmenopausal women, the ovaries stop producing estrogen and fat tissue then becomes the body’s main estrogen source. If these women are obese, the excess fat tissue may produce higher estrogen levels, potentially triggering a faster growth in some breast tumors.
Obesity’s cancer link doesn’t end with the risk of incidence. The excess weight is also linked to poorer outcomes, according to ASCO, including impacts on surgical results, prognosis, chemotherapy-related complications and an increased risk for secondary cancers. Because of these and other complications, treating overweight or obese cancer patients is much more complicated, says Dr. Ricardo Alvarez, Director of Cancer Research & Breast Medical Oncologist at our hospital near Atlanta. That’s why he typically spends a third of his time with patients discussing diet and exercise. “My suggestion to them is always to do a physical activity that they enjoy, such as swimming or Zumba®,” he says.
Of course, obesity isn’t just caused by poor diet and lack of exercise. Some people have a genetic predisposition to being overweight, says Dr. David Boyd, Intake Physician at our hospital near Phoenix. “In those cases, weight loss isn’t as easy as ‘energy in’ versus ‘energy out,’” he says. “When you look at different factors for different people, it gets more complex.”
Count lifelong battles with weight among those complexities, especially for future generations of cancer patients. With childhood obesity statistics at an all-time high, the condition is affecting more people earlier in life, meaning the connection between obesity and cancer may only become more challenging. “It wasn’t long ago that we started to see Type 2 diabetes in kids when we’d only ever seen Type 1 diabetes in kids,” Dr. Boyd says. “Think about it: We now live in a society where we don’t feel like we can send our kids outside to play unsupervised. That has impacted the health of our kids.”
Impact of childhood trauma
In other cases, childhood trauma may trigger eating disorders that become long-lasting, and difficult to treat. One large investigational study, for example, found that many of the obese patients surveyed about their childhood experiences reported that they suffered emotional, physical or sexual trauma when they were young. Along the way, after experiencing higher and more persistent levels of stress than their peers, a large number of them began using eating as a coping mechanism. “It’s not just a behavioral fix,” Dr. Eugene Ahn, Medical Director of Clinical Research & Hematologist/Oncologist at our hospital in Suburban Chicago, says. “There are a lot of mind-body and psychosocial aspects for individuals in terms of why they’re engaged in unhealthy lifestyles. If we have a more compassionate understanding of that, we’ll have more effective interventions for preventing or treating obesity.”
Lammersfeld says she thinks setting realistic goals is also key to overcoming obesity. “The biggest way we can help patients is by focusing on smart goals for them, such as losing 5 percent of their body weight, to start,” she says. “We have to try to help individuals, in the most supportive way possible, lose even small amounts of weight if they can, so they can have better outcomes.”
Dr. Alvarez has instituted a plan for a specific patient population—women with breast cancer—and is studying its effects. The idea came to him after learning, in 2015, that 82 percent of his breast cancer patients were overweight or obese. In November 2016, Dr. Alvarez launched the Energy Balance Research in Cancer (EnBaR) study to determine whether incorporating weight management and physical activity programs into cancer care would translate into better outcomes. As part of the study, the patients check in with a dietitian twice a month to discuss predetermined goals, such as level of activity, diet, smoking, alcohol, sleep and motivation, and to track progress. “We need to determine a clear strategy for how to tackle obesity,” Dr. Alvarez says, “especially because more and more cancer survivors are living longer.”
Cancer doesn’t discriminate, and prevention isn’t foolproof. But you do have important opportunities to take charge of your health, Dr. Boyd says. “You can’t change your genetics, but you can put in place lifestyle modifications from childhood,” he says. “Look at it this way: You don’t want to stack things in favor of developing cancer or, if you’re already diagnosed with cancer, to worsen your prognosis. You want to do everything you can to improve your odds.”
