Energy Balance

CURE, Fall 2010, Volume 9, Issue 3

Matching calories consumed to calories burned may reduce your risk of recurrence.

At 245 pounds, Teddy Viator, 58, of Dallas, Texas, underwent surgery for prostate cancer in September 2007. The surgery was a success, but Viator wasn’t out of the woods just yet. He learned that his weight increased his risk of a cancer recurrence.

So Viator started an aggressive weight loss program. “When the cancer hit me, it was a wake-up call,” Viator says. “I knew that if I wanted to live, I had to get the weight off. I wanted to improve my odds as best I could.”

Viator started out using a treadmill and an elliptical machine at their lowest settings, gradually building up from a slow walk to a brisk jog. He also took up weight training and dramatically changed his eating habits, eschewing his beloved fast food and red meat for a more healthy diet. Now, three years later, Viator weighs 182 pounds, has lost five inches off his waist, and runs 5Ks and mini-marathons on weekends.

The results, he says, have been life-changing. “I feel like I have a new lease on life,” Viator notes. “Before, I would just stay home and mope around. I never went anywhere. Now, I’m much more active.”

Researchers and clinicians have long known that being obese or overweight can tax the body in many destructive ways, from burdening our hearts, joints, and psyches to contributing to sleep problems, including snoring. And while some uncontrollable factors, such as genetics, age, and hormone levels, may contribute to being portly, researchers and health care professionals are increasingly concerned about obesity’s role in cancer recurrence—a fact substantiated by numerous studies—and are examining one approach to losing weight—a concept known as energy balance.

For Viator, balancing energy was fundamental to his weight loss. Quite simply, energy balance means consuming only as many calories as you expend via exercise and metabolism, explains Melinda Irwin, PhD, MPH, an associate professor in the division of chronic disease epidemiology at Yale School of Public Health. The dramatic increase in obesity in the United States over the past 20 years, she says, is at least partially the result of energy imbalance: we’re consuming too many calories and not burning enough.

In recent years, the onset of certain cancers, as well as poor prognosis and risk of recurrence, has become associated with weight or body composition. These cancers include postmenopausal breast, colon, ovarian, endometrial, liver, gallbladder, and esophageal cancers.

Obesity possibly affects the risk of cancer recurrence in several ways. One pathway is through sex hormones, such as estrogen and progesterone, both of which are known to increase risk of breast cancer. Premenopausal women produce most of their estrogen through their ovaries, Irwin explains. When they become postmenopausal, they stop producing estrogen via their ovaries, but continue to produce it in their fat tissue, where androgens, made primarily in the adrenal glands, are converted to estrogens. As a result, the more body fat a woman has, the higher her estrogen level.

Among many women with breast cancer, the standard of care is to use drugs that block or inhibit estrogen activity, such as tamoxifen or aromatase inhibitors. However, it is theorized that the effectiveness of these drugs may be influenced by the higher estrogen levels in women with higher body fat. Two recent studies, one published in the September 2009 Journal of Clinical Oncology and one presented at the 2010 American Society of Clinical Oncology annual meeting, showed that in patients with a high BMI who took the aromatase inhibitor Arimidex (anastrozole), a higher risk of recurrence was seen. A possible explanation is that higher levels of estrogen were overwhelming the protective effect of hormonal therapy.

A second pathway is insulin and insulin-like growth factors, which can stimulate cancer growth. Insulin sends signals to cells to grow, and can stimulate insulin-like growth factors to help in proliferation. Abnormally high cell growth rate can increase the likelihood of mutation, which could lead to cancer.

The third pathway is inflammation, a chronic disease state linked to all manner of illnesses. Obesity, too, is considered an inflammatory state, identified through markers such as C-reactive protein. These markers have been shown to decrease with weight loss, thus leading researchers to believe that the body’s inflammatory state diminishes with weight loss.

For many people, getting to a more healthy weight is achievable but may require a change in dietary habits. Many Americans are accustomed to diets based on red meat, fatty and processed foods, and refined grains. The National Cancer Institute and the American Cancer Society recommend a diet low in fat and red meat, and high in fruits, vegetables, whole grains, and fiber.

Exercise, of course, is equally important. Some cancer survivors may have issues, such as neuropathy and neutropenia, that affect their ability to work out, says Meyerhardt, but there are ways to find an effective substitute.

“When [researchers] have looked at the issue of physical activity on outcomes, it generally includes a variety of different activities that people report doing,” Meyerhardt explains. “That would include walking, running, racquet sports, and other aerobic activities. One is not better than the others. Anything that increases heart rate and leaves a positive energy expenditure is a good thing.”

It’s a misconception, Meyerhardt adds, that exercise alone will make the pounds melt away. While exercise burns calories, it also can stimulate hunger. So people who exercise more tend to make up the energy loss by increasing their caloric intake. In order to lose weight, you must change your diet and increase your level of physical activity.

Another misconception is that losing weight requires so much exercise that it’s impossible to achieve. “Though we don’t know exactly the minimum amount of exercise, it does seem like there is some gradation—that some exercise is better than none,” Meyerhardt reports. “And people who weren’t used to exercising before their cancer diagnosis need to be patient because it does take a while to build up to some level. But if you do it slowly and work with a trainer or exercise physiologist, you can slowly increase your level of activity to beneficial levels.”

Viator adds that acknowledging his own health issues and making a conscious decision to do something about them was a motivation for him.

“You have to change your whole mind-set about eating, and you have to incorporate exercise,” he says. “The old way of eating is passé. You can’t be lazy and just eat fast food—eventually, that will harm you. I have two sons and I’m trying to instill in them that they have to make good nutritional choices now and start exercising. Hopefully, my story will inspire others to change their lives.”

Other factors can also influence risk of adult obesity, such as being overweight as a child. According to Jeffrey A. Meyerhardt, MD, MPH, an assistant professor of medicine at Harvard Medical School and gastrointestinal oncologist at Dana-Farber Cancer Institute in Boston, studies strongly suggest that an obese child is much more likely to become an obese adult.

And even relatively healthy people can find themselves carrying unwanted extra pounds in their senior years as a result of age-related metabolic changes. As we age, we tend to lose bone and muscle mass. One reason is that we are not as active as we were when we were younger, Irwin explains. Certain cancer treatments can also lower bone density and muscularity, also slowing the metabolic rate. Consequently, when we expend fewer calories and do not adjust our caloric intake accordingly, the result can be an increase in body fat.

Genetics, too, can increase a person’s risk of obesity, sometimes through the development of certain endocrine diseases, like thyroid, metabolic, and hormonal problems, says Meyerhardt.

And then there are psychological factors. “I definitely think it’s a ‘chicken-or-the-egg’ thing,” observes Irwin. “Is it things like depression and anxiety and stress that lead to obesity, or is it that being obese makes you anxious, stressed, and depressed? Probably a little bit of both. But even if you are obese, exercise can improve these psychological factors over the short term.”

Several studies and reviews bear out the relationship between obesity and cancer risk, treatment outcome, and recurrence. In a 2007 study published in the Archives of Internal Medicine, researchers prospectively examined the relationship of obesity and adult weight change to breast cancer risk among 99,039 postmenopausal women in the National Institutes of Health—AARP Diet and Health Study. The result: weight gain throughout adulthood was found to be associated with increased postmenopausal breast cancer among women not using menopausal hormone therapy.

And in a 2008 study published in The Breast Journal, researchers performed a secondary analysis on 636 women with lymph node—positive breast cancer. They found that increased body mass index (BMI), a calculation based on height and weight, was generally predictive of a faster time to recurrence and decreased survival. Researchers also found that the relationship was stronger among younger women, those with progesterone receptor–negative disease, and those with a greater number of lymph nodes that were positive.

“Most studies have focused on breast or colon cancer, and for both of those cancers, low levels of activity have been strongly associated with poor prognosis,” Irwin says. “It’s the same with obesity—patients with a high BMI have a worse prognosis.”

Cancer researchers and health care professionals are increasingly concerned about obesity because of its role in cancer recurrence—a fact substantiated by numerous studies.

John Coughlin, 58, of Duxbury, Massachusetts, attributes a healthier diet and exercise to improving his prognosis. Diagnosed with stage 3 rectal cancer in September 2003, Coughlin—a cyclist already in pretty good shape—underwent a couple of big surgeries to treat his cancer. He started walking the moment he was able, first across his hospital room, then up and down the unit floor. His health improved enough that he was released from the hospital two days early.

“Being in good physical condition to begin with helped me endure treatment much better,” Coughlin says. “From the moment I came home, I made it a point to walk three to four miles every day, which made me much stronger.”