Obesity may increase the risk of cancer recurrence. Here's what you can do to counteract it.
In April, Otis W. Brawley, MD, chief medical and scientific officer of the American Cancer Society, expressed his concern that the declines in cancer mortality over the last 20 years have the potential to increase because of one factor.
“Today, a third of all cancers is caused by smoking and nearly a third of all cancers is caused by this combination of obesity, poor nutrition and physical inactivity,” Brawley said to the audience during a medical presentation. “Literally, over half of all cancers are caused by those two factors.”
According to the Centers for Disease Control and Prevention, 35.7 percent of adult Americans (more than 78 million) and around 17 percent (12.5 million) of children and adolescents ages 2 to 19 are obese, which is determined by calculating body mass index (BMI) using height and weight.
While estimates of the number of cancer cases linked to obesity varies, a study using the National Cancer Institute’s (NCI) SEER data calculated (or modeled) that, in 2007, more than 84,000 cancer diagnoses were associated with obesity. By 2030, when nearly half of all Americans are expected to be obese, the NCI estimates obesity will lead to an additional 500,000 cancer cases.
For survivors concerned about lessening their chances of a second cancer and reducing the legacy of cancer in their family, facing the facts about obesity becomes essential.
Though it sounds counterintuitive, fat cells are metabolically active. They can stimulate the production of hormones and other signaling substances that may affect the way malignant cells grow and reproduce. Possibly the best-known of these is estrogen, the female hormone linked to breast and endometrial cancers. Fat cells manufacture aromatase, which converts androgens to estrogens. Recent research shows that obese women with hormone receptor-positive breast cancer had a 30 percent higher risk of recurrence and about a 50 percent higher risk of death than normal-weight patients, despite optimal treatment and an otherwise healthy body.
Many survivors have lost muscle mass, which results in lower metabolism and weight gain.
Obesity can also cause the hormone insulin to become a biological villain. Poor eating habits and a lack of exercise can lead to excess insulin in the bloodstream. In some cancers, insulin can cause tumor cells to proliferate faster. Studies also show that patients with colorectal cancer and high levels of insulin are associated with an increased rate of mortality compared with those who have lower levels of insulin.
Though limited research exists concerning a link between obesity and cancer recurrence, there is no question that obesity is linked to many other comorbid conditions, such as diabetes and heart disease.
Managing obesity seems simple: Weight loss occurs when calories burned are greater than calories consumed. Not so for all cancer survivors, says Russell Kennedy, PsyD, a behavioral specialist formerly at Tufts University in Medford, Mass., who is now in private practice with his wife, Stacy Kennedy, a certified specialist in oncology nutrition, registered dietitian and senior clinical nutritionist at Dana-Farber/Brigham and Women’s Cancer Center in Boston.
“Once you’ve gone through treatment, your body is going to react differently to calories,” Russell Kennedy says. “You need to have compassion for yourself.”
He explains that many patients lose muscle mass during treatment. Lean muscles are the energy hub of the body, burning calories and expending energy even when the body is at rest. When muscle mass drops, so too does the body’s basal metabolic rate. Low metabolism can result in weight gain, as the body burns fewer calories than it takes in. This is one reason many survivors gain weight despite an unchanged diet.
In presentations they give throughout the Boston area on integrative weight management, the Kennedys stress that the best way to achieve sustainable weight loss is by customizing diet and exercise to fit an individual’s lifestyle.
Once you’ve gone through treatment, your body is going to react differently to calories.
“Making something customized really helps promote it as a lifestyle change,” says Stacy Kennedy, explaining that looking up a fad diet on the Internet is not going to work.
“When you understand that 50 percent of the population is on a diet at any given time, you understand that they aren’t effective,” she says. “Eating healthily needs to be customized to your schedule, your life and your physiology.”
She also recognizes that having a dietitian may not be possible for everyone but encourages patients to advocate for themselves to find resources to help, including taking information from reputable sites, such as danafarber.org/nutrition where, Kennedy says, there are recipes and answers to many common questions patients have asked.
Wendy Demark-Wahnefried, PhD, a registered dietitian and associate director for cancer prevention and control at the University of Alabama at Birmingham Comprehensive Cancer Center, is part of a research consortium that is studying the effects of weight loss on quality of life and other outcomes in women who have had breast cancer. The study, Exercise and Nutrition to Enhance Recovery and Good Health for You (ENERGY), is following more than 700 overweight and obese women up to five years post-diagnosis who are participating in the first clinical trial of its kind, where the goal is to lose 7 percent of their body weight.
“If you’re overweight, a weight loss of 5 to 7 percent can usually normalize a lot of the parameters in the blood, such as insulin and sex hormones, that become off balance,” she says.
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Valerie Cartee, a 43-year-old mother of two in Trussville, Ala., who received a diagnosis of stage 2, hormone receptor-positive breast cancer in 2009, is already reaping the benefits of the ENERGY study. During the course of treatment, she gained around 15 pounds, and her doctors instructed her to keep her weight down because fat cells produce estrogen.
To fit her lifestyle and help increase cardiovascular fitness, Cartee uses workout DVDs at home. Though not yet at her goal weight, she has lost 9 percent of her body weight since beginning the study, exceeding the goal of 7 percent.
I guess I didn’t realize how much it takes to lose weight. This is a process; it’s not a diet. It is a new lifestyle.
“For most women, a 7 percent weight loss is around 12 pounds,” says Demark-Wahnefried. “Many times women who lose 12 to 18 pounds don’t think it’s a lot, but it can make a big difference. What we know from other studies in diabetes and heart disease is that 7 percent weight loss will often normalize blood sugar and cholesterol.”
Cartee says the hardest thing to learn was that ideal weight loss happens slowly. She was often deflated to see less than a 1-pound loss some weeks. “I guess I didn’t realize how much it takes to lose weight,” she says. “This is a process; it’s not a diet. It is a new lifestyle.”
The women in the study are divided into two groups; the intensive group meets regularly to get support from each other about situations and how to handle them, she says. The other group gets individual counseling twice with a dietitian, and Demark-Wahnefried says a number of women in that group are making lifestyle changes without group support.
Russell Kennedy stresses that cancer survivors must first come to the understanding that their body has changed before moving on with diet and exercise changes. He emphasizes that they must first rediscover and form a positive relationship with their body.
“If you have a new body, you have a new intimacy,” he says. “The rules are not the same.” Forming a positive relationship with your body is important; to do this, it is necessary to develop a support system, he adds. This can be a family member or friend to fall back on during times of stress. Though losing weight is a physical process, a person is defined by more than their physiology, and “talk therapy” is a way of coping with stress other than eating.
Carole Covington, 65, never knew how much of a support system she had until she received a breast cancer diagnosis and needed to make lifestyle changes, recognizing she hadn’t taken care of herself in years, she says.
Covington signed up for the ENERGY trial at 30 pounds overweight. She counted calories each week in a book that she likened to a report card. Week by week, she slowly weaned herself off her daily candy treat.
“When you start eating healthier and you give up most of the bad stuff, your taste buds change,” she says. “I really do not crave all that chocolate like I used to.”
At her last group meeting of the trial, the nutritionist asked each of the women who their support would be after the group no longer met. For Covington, it was her husband, who does the grocery shopping and cooking, and her sister, who went through her own weight-loss experience and has maintained a healthy weight for two years. Covington met her 30-pound weight-loss goal and is confident she will stay on track for the remainder of the study and beyond.