The positive effects of a regular exercise routine are undeniable. Increased physical fitness lowers risk for a host of medical issues, including heart disease and diabetes, according to the Mayo Clinic. And the benefits for people currently in treatment for cancer are just as worthwhile—when paired with proper nutrition, exercise can help cancer fighters improve their response to chemotherapy, reduce the risk of cancer recurrence, and increase their quality of life.
Cachexia, or muscle wasting, is a significant side effect of cancer treatment. According to Dr. Tina Skinner, a professor of clinical exercise physiology at Australia’s University of Queensland, cachexia is especially relevant to hormone-related cancers (like breast and prostate cancers). Cachexia reduces hormone production—which is a positive effect for these cancers, as the tumor has nothing to feed on and grow—but also contributes to a loss of muscle mass, an increase in body fat percentage, and reductions in bone mass. “Those who have more muscle mass to start with, [experience] less of those cachexia effects,” Skinner says. “There is a strong relationship between muscle loss and mortality from cancer.”
According to a June 2013 paper in the Journal of Cachexia, Sarcopenia and Muscle, the cause-and-effect relationship between cachexia and death is widely unknown. “Despite the strong and consistent association of cachexia with mortality, no unifying mechanism has yet been suggested as to why wasting conditions are associated with an exceptionally high mortality risk,” the paper states.
Even so, the most significant benefit of regular exercise on cancer patients is decreased body fat. “An increase in percent body fat increases your risk of not only cancer, but cancer recurrence,” says Dr. Harold Bays, the medical director of the Metabolic and Atherosclerosis Research Center in Louisville, Kentucky. According to Bays, an increase in fat cells leads to inflammation, hormone dysfunction, and an increase in insulin production, all of which contribute to cancer. Bays advises proper nutrition and exercise to maintain a healthy body weight, ward off cancer, or, for those in treatment, promote the effects of their treatment regimen and decrease the risk of recurrence.
The numbers don’t lie. A December 2018 study published in JAMA Oncology says “the proportion of cancers attributable to excess body weight ranges from 3.9% to 6.0% among men and from 7.1% to 11.4% among women.”
The risks are of special concern for people with prostates. While high-fat diets alone do not cause lethal prostate cancer diagnoses, a January 2018 study published in Nature Genetics linked high-fat diets with more aggressive prostate cancer diagnoses, which are typically lethal. Prostate cancer begins when a protective gene, PTEN, shuts down, but the cancer rarely spreads beyond the prostate. However, when consuming a high-fat diet, prognosis worsens. In the JAMA Oncology study, researchers used mice with prostate cancer—when their diet switched from low-fat vegetarian to a high-fat “Western” diet (a diet of high-fat pellets containing sugar, starch, and other ingredients not found in the low-fat pellets), their previously treatable prostate cancer significantly metastasized.
Regular exercise in cancer patients doesn’t just help them drop pounds or maintain a healthy body weight; it can actually decrease tumor size. “There’s new emerging evidence, really strong evidence, suggesting that [exercise] actually has a direct effect, not only on the tumor itself, but also on the tumor marker environment,” says Skinner, who was on a team of researchers who conducted a study examining the effects of moderate- and high-intensity exercise on men with colorectal cancer.
“What we’re trying to do in our lab is to [determine] what’s the dose, what’s the frequency, what’s the intensity, what’s the type, and what’s the time of exercise required to not only optimize either your ability to survive your cancer and reduce disease- and treatment-related side effects, [but also] reduce recurrence,” Skinner says.
The optimum dose, of course, is relative to every person, and this is the question Skinner and her team are attempting to answer. Interestingly enough, an October 2018 study published in JAMA Oncology found the optimum dose of exercise to improve longevity for people who survived cancer as children is around one hour of brisk walking most days of the week.
For current cancer fighters, exercise releases adrenaline, and higher-intensity exercises produce higher levels of adrenaline responses, according to Skinner. “That higher release of adrenaline results in kind of this myriad of other blood-related, anti-tumor effects,” says Skinner. This has a variety of positive health effects on inflammation, blood glucose levels, and insulin sensitivity—all components of cancer progression.
Of course, many forms of exercise are unattainable for some fighting especially aggressive cancers, but Skinner says it’s all relative to the patient. “If we’ve got men who are very unwell and unable to reach that optimum dose, [we’re trying to find] what’s the minimum amount of exercise that would be able to optimize their outcomes,” Skinner says.
And it’s best to start exercising now to continue reaping the benefits later. An April 2019 article from The New York Times considered a new study published in Frontiers in Physiology that researched participants in an exercise study conducted ten years ago who still feel the benefits of exercise today.
Over the course of eight months, groups participated in regular exercise regimes ranging in moderate to intense. Ten years later, the intense exercisers were markedly more fit than the control group (those who did not adopt a new exercise regime in the original study). The moderate exercisers lost more fitness overall, but had healthier blood pressure and insulin sensitivity than the control group. More research needs to be conducted, but according to Dr. William Kraus, the lead researcher on the study, exercise “probably leaves long-lasting imprints on our genes and cells that affect health.”
At the core of it, exercise in any form is imperative for quality-of-life factors for fighters who are well enough to move about the world unassisted. “It’s a vicious cycle,” Skinner says. “When you can’t get out of a chair, then you lose your independence.” For some, then, regular exercise could lead to lasting improvements in both their mental and physical health, during and after their cancer treatment.