Story at-a-glance

• Evidence shows exercise not only is a key component of effective cancer prevention, but also cancer treatment and prevention of recurrence
• Strong evidence exists showing that exercise lowers your risk of developing colon, breast, endometrial, kidney, bladder, esophageal and stomach cancer. The link between exercise and a lower risk for lung cancer is moderately strong
• An international team hopes to shift the paradigm of cancer treatment by 2029, to include prescribed exercise as part of standard care
• To help with the implementation of the new guidelines into clinical practice, the American College of Sports Medicine’s Exercise Is Medicine initiative has launched a new program called Moving Through Cancer
• Based on the scientific evidence, the recommended amount of exercise for cancer patients is up to 30 minutes of moderate‐intensity aerobic activity three times a week, and up to 20 or 30 minutes of resistance exercise twice a week

Cancer is at epidemic proportions around the world. An estimated 1,762,450 Americans are expected to be diagnosed with cancer in 2019,1 and approximately 1,663 die from it every day.2 Based on what we now know about the origins of cancer, it's clear that this avalanche is largely the result of inappropriate diets and unhealthy living. Lack of exercise is part of this.

Evidence shows exercise not only is a key component of effective cancer prevention, but also cancer treatment and prevention of recurrence, so it's really a triple-win. I first heard of this about 30 years ago and was delighted but surprised and did not understand how this could occur, but now the physiology is well understood as I discuss further below.

Not surprisingly, few oncologists ever tell their patients to engage in exercise beyond their simple daily, normal activities, and many cancer patients are reluctant to exercise, or even discuss it with their oncologist. This may soon change.

As reported in an October 16, 2019, press release,3 an international team, led by Kathryn Schmitz, Ph.D., professor of public health sciences at Penn State College of Medicine, is now hoping to shift the paradigm of cancer treatment by 2029, to include prescribed exercise as part of standard care. As reported by the American College of Sports Medicine:4

"New guidance from exercise oncology experts recommend systematic use of an 'exercise prescription' by health care workers and fitness professionals in designing and delivering exercise programs that aim to lower the risk of developing certain cancers and best meet the needs, preferences and abilities of people with cancer."

Exercise To Be Prescribed Like Medicine

A comprehensive scientific review of the evidence and new exercise guidelines for cancer patients is detailed in three separate papers published in two scientific journals:

1. "Exercise Guidelines for Cancer Survivors: Consensus Statement from International Multidisciplinary Roundtable" published in Medicine & Science in Sports & Exercise5
2. "American College of Sports Medicine Roundtable Report on Physical Activity, Sedentary Behavior, and Cancer Prevention and Control" published in Medicine & Science in Sports & Exercise6
3. "Exercise Is Medicine in Oncology: Engaging Clinicians to Help Patients Move through Cancer" published in CA: A Cancer Journal for Clinicians7

In their CA: A Cancer Journal for Clinicians paper,8 Schmitz and her team urge cancer patients and oncologists to take exercise prescriptions to heart:

"Multiple organizations around the world have issued evidence‐based exercise guidance for patients with cancer and cancer survivors. Recently, the American College of Sports Medicine has updated its exercise guidance for cancer prevention as well as for the prevention and treatment of a variety of cancer health‐related outcomes (eg, fatigue, anxiety, depression, function, and quality of life).

Despite these guidelines, the majority of people living with and beyond cancer are not regularly physically active. Among the reasons for this is a lack of clarity on the part of those who work in oncology clinical settings of their role in assessing, advising, and referring patients to exercise.

The authors propose using the American College of Sports Medicine's Exercise Is Medicine initiative9 to address this practice gap. The simple proposal is for clinicians to assess, advise, and refer patients to either home‐based or community‐based exercise or for further evaluation and intervention in outpatient rehabilitation."

Exercise Prescriptions — A New Part of Standard Cancer Care

The team goes on to propose a plan for clinical implementation, which would include:10

• Care coordination with appropriate fitness professionals
• Behavioral changes among clinicians, patients and fitness experts/rehabilitators alike
• Improving referrals
• Implementing an exercise program registry
• Addressing costs and compensation for exercise programs, as well as developing the needed workforce

"In conclusion, there is a call to action for key stakeholders to create the infrastructure and cultural adaptations needed so that all people living with and beyond cancer can be as active as is possible for them," the authors write.11

To help with the implementation of the new guidelines into clinical practice, the American College of Sports Medicine's (ACSM) Exercise Is Medicine initiative has launched a new program called Moving Through Cancer.12

This "clinician-focused program aims to ensure that all people living with and beyond cancer are assessed, advised, referred to and engaged in appropriate exercise and rehabilitation programming as a standard of care," ACSM explains.13

Cancer Patients Benefit From Exercise in Many Ways

The CA: A Cancer Journal for Clinicians paper cites a number of studies demonstrating the benefits of exercise for patients with cancer. For example, strong evidence exists showing that exercise lowers your risk of developing colon, breast, endometrial, kidney, bladder, esophageal and stomach cancer.14

The link between exercise and a lower risk for lung cancer is moderately strong, while the evidence for it lowering your risk of certain other cancers is limited. They also cite evidence showing that exercise improves cancer survival after diagnosis, especially for those with breast, colon and prostate cancer.15

There's also strong evidence that exercise reduces anxiety, depressive symptoms, fatigue and physical function in cancer patients, and moderate evidence showing it improves sleep.16

"In summary, the scientific evidence base supports exercise, and patients and clinicians generally agree that patients should be moving throughout their cancer therapy and survivorship," the authors state.17

"The primary goal of this article is to address the above-noted barriers to oncology clinicians making exercise referrals standard practice, including the provision of straightforward tools intended to make it easier for clinicians to recommend and refer patients to safe, effective, and appropriate exercise programming. Other professionals can then take over for further assessment, triage, referral, or intervention, as appropriate."

Exercise Recommendations for Cancer Patients

Based on the scientific evidence, the recommended amount of exercise for cancer patients is up to 30 minutes of moderate‐intensity aerobic activity three times a week, and up to 20 or 30 minutes of resistance exercise twice a week.

This level of exercise has been shown to be a "safe and effective dose to address anxiety, depressive symptoms, fatigue, quality of life and physical function deficits," the authors state.18

The first chart below offers summary guidance for oncologists to help them tailor their exercise prescriptions to the patient's ability. The second is a sample "exercise prescription pad" that clinicians can download19 and use.

Additional resources for oncologists and patients, including a searchable registry of various exercise programs can be found on the ACSM's Moving Through Cancer website.20

Evidence Linking Exercise to Lower Cancer Risk

As reported by The New York Times,21 while exercise recommendations for cancer patients were published nearly a decade ago, in 2010,22 they fell short. All the researchers were really able to conclude was that exercise appeared to be safe for most cancer patients, and "The advice to 'avoid inactivity,' even in cancer patients with existing disease or undergoing difficult treatments, is likely helpful." The New York Times writes:23

"Since then, however, there has been 'exponential growth' in research related to exercise and cancer, says Kathryn Schmitz … the immediate past president of the American College of Sports Medicine.

So, last year, she and almost 40 other researchers from 17 international health groups gathered to determine whether there was sufficient evidence now to refine the recommendations about cancer and exercise.

The group wound up gathering hundreds of studies involving animals and people that examined the impacts of exercise on dozens of aspects of cancer risk and cancer recovery.

And they concluded that there was more than enough evidence to start suggesting that exercise should be a part of standard treatment for most people with cancer. They also found that exercise should be considered a means to substantially drop the risk of developing cancer in the first place.

The recommendations also point out that, in multiple recent studies, exercise changed the trajectory of cancer once it began.

In animal experiments cited in the new reviews, exercise altered the molecular environment around some tumors, stalling or even halting their growth. And in people, exercising during and after cancer treatment was associated with longer subsequent life spans …"

Below, I've included short summaries of just a few of the studies that have emerged over the years, showing that exercise is an important prevention method and effective treatment adjunct for cancer. 

• The degree to which exercise cuts your cancer risk varies depending on the type of cancer and other factors, but the data show physically active individuals have a 20% to 55% lower risk of cancer than their sedentary peers. For example, compared to inactive people, active men and/or women have a:

◦ 20% 30% lower risk of breast cancer24

◦ 38% reduced risk of invasive breast cancers25

◦ 30% to 40% lower risk of colon cancer26

◦ 32% lower risk of all cancer-related deaths27

◦ 55% lower risk of lung cancer28

• Research29 published in 2015 found that mice that exercised on a motorized treadmill for an hour each day, five days a week for 32 weeks, experienced fewer incidents of liver cancer than sedentary mice.

Hepatocellular carcinoma (HCC) is a cancer that originates in your liver cells, and is one of the most common types of cancers, causing an estimated 31,780 deaths in the U.S. annually.30

According to this study,31 which was the first of its kind for this type of tumor, regular exercise may be the key to significantly reducing your chances for developing liver cancer. Regular exercise has also been shown to reduce your risk of nonalcoholic fatty liver disease, brought on by an unhealthy diet, thereby cutting your risk of HCC.32

• A 2015 study33 found aerobic exercise slowed the growth of breast cancer tumors in mice. By increasing tissue oxygenation, it also improved the effectiveness of chemotherapy. As reported by The New York Times,34 "The results raise the possibility that exercise may change the biology of some malignant tumors, potentially making them easier to treat."

• A 2016 analysis35,36 of data from 1.4 million people of a wide range of ethnic backgrounds from both the U.S. and Europe over the course of 11 years found those who exercised more had, on average, a 7% lower risk of developing any kind of cancer.

• A 2019 study37 from the Henry Ford Health System in Detroit, Michigan, and Johns Hopkins School of Medicine found the fittest adults have the lowest risk of lung and colorectal cancers.

At a median follow-up of 7.7 years, those in the highest fitness category had a 77% reduced risk of lung cancer and a 61% decrease risk of colorectal cancer. Additionally, those in the highest fitness range had a 44% reduced risk of death when diagnosed with lung cancer and an 89% reduced risk of death when diagnosed with colorectal cancer.38

Exercise Lowers Risk of Cancer Recurrence

Exercise not only helps cancer patients recuperate faster, but it also diminishes the risk of cancer recurrence. For example, research shows patients who engage in high amounts of exercise after being diagnosed with colorectal cancer have a 42% lower total mortality risk and a 39% lower risk of colorectal cancer–specific mortality than those who get little exercise after their diagnosis.39

Similarly, breast cancer patients with higher exercise levels have a 29% to 41% lower risk of dying from breast cancer.40 A 2019 study41 published in The Journal of Physiology found high-intensity interval exercise (HIIE) specifically reduced the risk of death among colorectal cancer patients.

Patients participated in 12 HIIE sessions over a four-week period, and blood samples drawn immediately after the exercise were found to reduce the number of colon cancer cells in a petri dish. A significant increase in cytokines signaling proteins responsible for modulating the immune and inflammatory response was also observed. According to the authors:42

"The acute effects of HIIE and the cytokine flux may be important mediators of reducing colon cancer cell progression. Repetitive exposure to these acute effects may contribute to the relationship between exercise and improved colorectal cancer survival."

How Exercise Combats Cancer

So just how does exercise prevent cancer? Research shows there are many pathways and mechanisms at play; a synergistic orchestra of chemical reactions if you will, triggered by physical exertion. For example, exercise decreases your risk of cancer by:

Improving insulin sensitivity — One of the key mechanisms responsible for driving down your cancer risk is the fact that exercise decreases your insulin resistance. By creating a low sugar environment in your body, the growth and spread of cancer cells are significantly discouraged.

Improving blood circulation — Exercise also improves circulation, driving more oxygen into your tissues and circulating immune cells in your blood. By improving blood flow to your liver, it also helps your body detoxify potentially harmful substances, including excess estrogen that may spur estrogen-sensitive cancers such as breast cancer.

Improving mitochondrial function — Mitochondrial damage can trigger genetic mutations that can contribute to cancer, so optimizing the health of your mitochondria is a key component of cancer prevention. In fact, mitochondrial dysfunction is at the core of virtually all diseases.

Exercise is one of the most potent stimulators of PGC-1alpha which stimulates mitochondrial biogenesis or production of new mitochondria. It does this by lowering mTOR, insulin and leptin levels which also improves mitochondrial autophagy (mitophagy) which is a key element of controlling malignant growth.

I review some of these details in my interview with Travis Christofferson's about his book, "Tripping Over the Truth: The Return of the Metabolic Theory of Cancer Illuminates a New and Hopeful Path to a Cure." This book is a must-read for anyone interested in preventing or recovering from cancer.

Stimulating AMPK, SIRT1 and inhibiting mTOR — Exercise stimulates AMPK and SIRT1, which secondarily inhibits mTOR, which then stimulates mitochondrial biogenesis and mitophagy, both of which are deadly to cancer.

In essence, cancer can be viewed as a metabolic disorder, and the key to prevention and recovery lies in restoring mitochondrial function and increasing mitochondrial numbers. Exercise helps you do both.

Improving energy balance, immune function and more — Exercise affects several biological functions that may directly influence your cancer risk, including changes in energy balance, immune function, antioxidant defense, DNA repair, bowel motility and hormone levels.43

Reducing body fat — Excess weight is a significant risk factor, and obesity is responsible for nearly 500,000 cancer cases worldwide each year.44 The link between obesity and cancer is primarily hormone-driven, as fat cells produce excess estrogen.

This also helps explain why exercise during childhood reduces your lifetime cancer risk, and why obese children are at a significantly heightened risk of cancer in their adult years.

Boosting adrenaline-dependent killer cells — Physical activity triggers the release of adrenaline, which in turn helps circulate natural killer (NK) immune cells into tumors in your lung, liver and skin, where they go to work to kill off and eliminate the cancerous cells.

The key that allows adrenaline-dependent NK cells to infiltrate cancer tumors is the immune signaling molecule, IL-6, which is released by muscle tissue during exercise. Without IL-6, the adrenaline cannot produce this anti-cancer effect, because the IL-6 molecules are what guide the immune cells to the tumors.45,46,47,48

Boosting effectiveness of T-cells — Exercise alters T cells to a more effective disease-fighting form, called "naïve" T cells, which boosts the ability of your immune system to fight emerging and existing cancer cells. This helps explain why exercise is beneficial both for cancer prevention and treatment.49

Exercise Is an Important Component of Cancer Treatment

There's no denying that exercise can have a profound impact on your health, and a major part of its benefit lies in its ability to prevent and treat disease. Cancer is just one in an inordinately long list of health problems that can arise as a result of chronic inactivity.

Ideally, you'll want to establish a comprehensive exercise program that includes high-intensity exercises and strength training — both of which have been shown to be of particular benefit for cancer prevention. My favorite exercise is blood flow restriction training.

I also urge you to consider walking more, in addition to your regular workout regimen. Ideally, aim for 10,000 to 15,000 steps per day. Also avoid sitting as much as possible. Ideally, limit your sitting to three hours a day or less.

Naturally, if you have cancer or any other chronic disease, you will need to tailor your exercise routine to your individual circumstances, taking into account your fitness level and current health.

Often, you will be able to take part in a regular exercise program with very little changes necessary. However, at times you may find you need to exercise at a lower intensity, or for shorter durations. Always listen to your body and if you feel you need a break, take time to rest.

But even exercising for just a few minutes a day is better than not exercising at all, and you'll likely find that your stamina increases and you're able to complete more challenging workouts. 

If your immune system is severely compromised, you may want to exercise at home instead of visiting a public gym. But remember that exercise will ultimately help to boost your immune system, so it's very important to continue with your program even if you suffer from chronic illness or cancer.

The fact that this international team of researchers is now pushing to make exercise prescriptions a part of standard care for cancer patients is really great news, and may go a long way toward lowering current mortality statistics.

The key is implementation, and as a patient, you can help your doctor get used to the idea of prescribing exercise by making sure you discuss these new guidelines with him or her during one or more of your appointments.