Rethinking Cancer Through a Lifestyle Lens

Cancer has long been seen as a matter of genetics and fate—something that happens to us, out of our control. But emerging research over the past few decades tells a more empowering story. While genetics certainly play a role in cancer risk, scientists now estimate that at least 30–50% of all cancers could be prevented through modifiable lifestyle choices, with some estimates even higher when accounting for broader environmental exposures. Among the most influential lifestyle factors are diet and physical activity—two areas within reach for most people.

This shift in understanding reframes cancer not merely as a biological accident, but as a disease deeply influenced by the conditions in which our cells live. What we eat, how often we move, how we sleep, and how we manage stress all help shape the “terrain” in which cancer may either take root or fail to thrive. Importantly, this influence doesn’t stop once cancer is diagnosed. Evidence is mounting that healthy lifestyle changes—especially those related to nutrition and exercise—can improve treatment outcomes, reduce side effects, and even lower the risk of recurrence.

This paper explores the current research on how much of a difference diet and exercise really make in both preventing cancer and in supporting treatment and survivorship. While the science is complex, the core message is simple: your everyday choices matter more than you might think.

The Power of Lifestyle: How Exercise and Diet Influence Cancer Prevention and Treatment

The Overview

  • Lifestyle Choices Significantly Impact Cancer Prevention and Treatment: Emerging research indicates that 30-50% of all cancers could be prevented through modifiable lifestyle choices, primarily diet and physical activity. These factors influence the cellular environment, affecting whether cancer takes root or thrives. The positive influence of healthy lifestyle changes, particularly nutrition and exercise, extends to improving treatment outcomes, reducing side effects, and lowering the risk of recurrence.

  • Biological Mechanisms Link Lifestyle to Cancer Risk: Lifestyle factors like poor diet and inactivity contribute to chronic inflammation, insulin resistance, oxidative stress, and immune dysfunction, all of which promote cancer development. Diet and physical activity can also modify gene expression through epigenetic mechanisms, influencing pathways related to inflammation, metabolism, and immune function. These synergistic effects actively participate in regulating cancer development and progression.

  • Exercise is a Potent Cancer Prevention Tool: Strong epidemiological evidence links regular physical activity to a reduced risk of several major cancers, including colon, postmenopausal breast, and endometrial cancers. The protective effect is dose-dependent, with even moderate activity offering significant benefits. Biological mechanisms include lower hormone levels, improved insulin sensitivity, decreased systemic inflammation, and enhanced immune surveillance.

  • Exercise Benefits Patients During Cancer Treatment: Contrary to past beliefs, physical activity is now actively recommended during and after cancer treatment. It significantly improves physical function, reduces debilitating cancer-related fatigue, and preserves lean body mass. Exercise may also enhance treatment efficacy by improving chemotherapy completion rates, increasing tumor oxygenation, and mobilizing immune cells to fight cancer.

  • Dietary Patterns are Crucial for Cancer Prevention: Overall dietary patterns, rather than individual foods, are key to influencing cancer risk. The Mediterranean diet and plant-predominant diets, rich in fiber and phytochemicals, are associated with reduced cancer incidence. Conversely, ultra-processed foods, high consumption of red and processed meats, refined sugars, and alcohol are linked to increased cancer risk.

  • Nutrition is Vital During Cancer Treatment: Maintaining a nourishing and balanced diet during cancer treatment is critical for patient well-being and treatment response. Malnutrition is a common challenge that can lead to worse treatment tolerance and reduced survival. Nutrition helps preserve muscle mass, reduce inflammation, promote healing, and prevent treatment interruptions due to side effects.

  • Synergistic Benefits of Combining Diet and Exercise: The combined effect of healthy eating and regular physical activity is more powerful than focusing on just one behavior. Studies show significantly greater reductions in cancer risk and recurrence for individuals adopting both. This synergy is due to complementary biological effects that reshape the body's internal environment to discourage cancer.

  • Challenges and Controversies Exist in Lifestyle Research: Despite strong evidence, some areas in nutrition and exercise science remain complex and unresolved, such as the role of soy in breast cancer or the efficacy and safety of high-dose supplements. The ketogenic diet and fasting during chemotherapy are promising but require further research and caution. Lifestyle modifications are modulators of risk, not guarantees against cancer.

  • Addressing Health Equity is Crucial for Broader Impact: Lifestyle interventions' promise is limited by unequal access to healthy food, safe exercise spaces, and integrative care, especially in lower-income and minority communities. Effective cancer prevention requires addressing structural inequities through community programs, urban planning, and insurance coverage for nutrition and exercise counseling. Health equity is essential for making healthy choices accessible to all.

Rethinking Cancer Through a Lifestyle Lens

To understand how lifestyle affects cancer, we need to look at the biological terrain—the internal environment that influences whether a cancerous cell is eliminated, grows, or spreads. Cancer doesn’t arise overnight; it develops gradually through a series of genetic and epigenetic changes that allow cells to escape the usual controls on growth and death. This process is shaped not just by inherited mutations, but also by environmental inputs, including what we eat, how much we move, and the state of our metabolism and immune system.

Several major processes tied to lifestyle play a key role in cancer risk:

  • Chronic inflammation, often driven by poor diet and inactivity, promotes mutations and creates a tumor-friendly environment.

  • Insulin resistance and excess insulin-like growth factors (IGF-1) encourage cell proliferation and survival, especially in cancers like breast, prostate, and colon.

  • Oxidative stress, often exacerbated by nutrient-poor diets, damages DNA and cellular machinery.

  • Immune dysfunction, influenced by both exercise and diet, reduces the body’s ability to detect and eliminate rogue cells.

In addition, lifestyle factors can modify gene expression through epigenetic mechanisms—essentially turning genes on or off without changing the DNA itself. For example, certain compounds in plant foods (like sulforaphane or resveratrol) can influence tumor suppressor gene activity. Regular exercise has been shown to influence gene expression in pathways related to inflammation, metabolism, and immune function.

In this context, diet and physical activity are not simply preventative—they actively participate in the biological regulation of cancer development and progression. And when combined, their effects are synergistic.

Exercise and Cancer Prevention: What the Research Shows

The evidence linking physical activity to cancer prevention is among the strongest in lifestyle medicine. Dozens of large-scale epidemiological studies, including the Nurses’ Health Study and the European Prospective Investigation into Cancer and Nutrition (EPIC), have found a consistent association between higher levels of physical activity and lower risk of several major cancers.

For example:

  • Colon cancer risk is reduced by about 20–30% in people who engage in regular moderate to vigorous physical activity.

  • Postmenopausal breast cancer shows a 20–25% risk reduction among active women compared to sedentary ones.

  • Endometrial cancer risk decreases by up to 30% in active individuals.

  • There is growing evidence for protection against lung, liver, esophageal, and kidney cancers, although the evidence is not yet as strong.

Importantly, this protection appears to be dose-dependent: the more consistently a person moves, the greater the benefit. However, even moderate activity (such as brisk walking 30 minutes a day) shows significant effects. The World Health Organization recommends at least 150–300 minutes of moderate-intensity aerobic physical activity per week, or 75–150 minutes of vigorous activity—standards that are backed by cancer prevention data.

Biological mechanisms that may explain this protection include:

  • Lower circulating levels of estrogen and other sex hormones in women, reducing hormone-driven cancer risk.

  • Improved insulin sensitivity, which reduces cell proliferation signals.

  • Decreased systemic inflammation, as shown by reductions in C-reactive protein (CRP) and interleukin-6 (IL-6).

  • Enhanced immune surveillance, particularly the activity of natural killer (NK) cells and cytotoxic T lymphocytes, which help identify and eliminate early cancer cells.

What’s encouraging is that these benefits occur regardless of weight loss. Even people who do not lose weight still see a reduction in cancer risk through regular exercise, suggesting that the act of moving itself is biologically protective.

Exercise During Cancer Treatment: Strengthening the Body’s Defenses

Once a person is diagnosed with cancer, it might seem intuitive to rest, conserve energy, and avoid strenuous activity. But over the past two decades, a profound shift has occurred in how clinicians view exercise during cancer treatment. Far from being discouraged, physical activity is now actively recommended during and after treatment, with a growing body of evidence supporting its safety, effectiveness, and ability to improve outcomes.

A landmark report from the American College of Sports Medicine (ACSM) concluded that exercise is not only safe during chemotherapy, radiation, and surgery but that it can significantly improve physical function, reduce fatigue, preserve lean body mass, and enhance quality of life. More than 200 clinical trials have examined this question, and their findings are striking.

One of the most debilitating symptoms during cancer treatment is cancer-related fatigue, a persistent, exhausting tiredness that does not improve with rest. Exercise—especially aerobic activity like walking, cycling, or swimming—has been shown to be one of the most effective interventions for managing this fatigue. In fact, patients who remain active during treatment often report less fatigue than those who are inactive.

Beyond symptom management, exercise may also improve treatment efficacy. For example, physical activity has been shown to:

  • Improve chemotherapy completion rates by maintaining strength and reducing toxicity.

  • Enhance blood flow to tumors, increasing oxygenation and making tumors more sensitive to radiation and certain drugs.

  • Reduce inflammation and immunosuppression, creating a less favorable environment for cancer growth.

  • Promote apoptosis (programmed cell death) in cancer cells, as shown in some early animal and human studies.

Emerging data also suggest that exercise may directly alter tumor biology. A 2020 study published in Cancer Cell found that exercise mobilizes immune cells—especially natural killer (NK) cells—into tumors, increasing their ability to fight cancer. Another small clinical trial in esophageal cancer patients showed that patients who exercised during chemotherapy had a significantly greater infiltration of immune cells into their tumors, potentially making treatment more effective.

Clinical programs known as “prehabilitation”—which involve physical training before surgery or intensive therapy—have also shown promise. Patients who engage in even brief exercise regimens before cancer surgery experience fewer complications, shorter hospital stays, and faster recovery.

In sum, exercise is no longer an optional “extra” for people with cancer—it is increasingly seen as a critical part of comprehensive cancer care. And as survivorship improves, physical activity plays a central role in reducing recurrence and improving long-term outcomes.

Diet and Cancer Prevention: Patterns and Nutrients that Matter

What we eat every day profoundly shapes our long-term cancer risk. While individual foods or nutrients can be studied in isolation, modern research increasingly focuses on overall dietary patterns—how combinations of foods interact to create either a protective or a high-risk internal environment.

Among the most well-researched dietary patterns linked to cancer prevention is the Mediterranean diet, which emphasizes fruits, vegetables, legumes, whole grains, nuts, olive oil, and moderate amounts of fish and wine. This way of eating is associated with reduced incidence of colorectal, breast, and gastric cancers, and improved survival among cancer patients.

Similarly, plant-predominant diets—those rich in fiber, phytochemicals, and antioxidants—appear protective against a wide range of cancers. Fiber, found abundantly in fruits, vegetables, legumes, and whole grains, is especially important. High-fiber diets are linked to lower colorectal cancer risk, in part because they feed beneficial gut bacteria, reduce inflammation, and bind carcinogens in the colon.

In contrast, ultra-processed foods and high consumption of red and processed meats are associated with increased cancer risk. The International Agency for Research on Cancer (IARC) classifies processed meats (like bacon, ham, and sausages) as Group 1 carcinogens—on par with tobacco and asbestos in terms of evidence strength, though not magnitude of risk. These foods are particularly implicated in colorectal cancer.

Other harmful dietary components include:

  • Refined sugars and sugary beverages, which can fuel insulin resistance and promote inflammation.

  • Alcohol, which increases the risk of at least seven types of cancer, including breast, liver, and oral cancers.

  • Trans fats and excess omega-6 fatty acids, which drive inflammatory pathways.

On the other hand, certain bioactive compounds in foods show anti-cancer potential:

  • Sulforaphane, found in broccoli sprouts, supports detoxification and may inhibit cancer stem cells.

  • Curcumin, the active compound in turmeric, has anti-inflammatory and anti-proliferative effects in lab models.

  • Flavonoids in berries, apples, tea, and cocoa exhibit antioxidant and anti-angiogenic properties.

Perhaps one of the most exciting areas of research involves the gut microbiome. Diet is the primary influence on gut flora, and studies show that microbial balance can affect not only cancer risk but also how patients respond to treatment. Diets rich in plant fiber and low in processed foods promote a diverse, stable microbiome, which in turn helps regulate immune responses and inflammation.

The takeaway is clear: diets emphasizing whole, unprocessed, plant-rich foods—and minimizing pro-inflammatory, ultra-processed options—are among the most powerful tools we have to reduce the risk of cancer.

Diet During Treatment: Supporting Recovery and Reducing Side Effects

Nutrition becomes even more critical once cancer treatment begins. Chemotherapy, radiation, surgery, and immunotherapy can all tax the body’s nutritional reserves, impair digestion, and disrupt metabolic balance. Maintaining a nourishing, balanced diet during this time can make a significant difference—not only in how patients feel, but in how well they respond to treatment.

One of the most immediate challenges is malnutrition, which affects up to 80% of cancer patients depending on the type and stage of disease. Muscle wasting (cachexia), loss of appetite, nausea, and taste changes can all interfere with adequate intake. Poor nutritional status is linked to worse treatment tolerance, lower quality of life, increased infections, and reduced survival.

In this context, nutrition serves multiple purposes:

  • Preserving muscle mass and immune competence

  • Reducing inflammation and oxidative stress

  • Promoting healing after surgery or tissue damage

  • Preventing treatment interruptions due to side effects or weakness

Some patients benefit from anti-inflammatory diets rich in omega-3 fatty acids, leafy greens, colorful fruits, and low-glycemic carbohydrates. These foods may reduce fatigue, brain fog, and inflammation-related symptoms.

A more experimental frontier involves targeted dietary strategies during chemotherapy. Preliminary studies on intermittent fasting or fasting-mimicking diets suggest that short-term calorie restriction before and during treatment may protect normal cells and increase the sensitivity of cancer cells to chemotherapy. While not yet standard of care, these approaches are undergoing clinical trials.

Another area of interest is the ketogenic diet, which restricts carbohydrate intake to reduce glucose availability. Some cancers thrive on glucose metabolism (the Warburg effect), and early studies suggest that a ketogenic diet might slow growth in some tumor types. However, results are mixed, and this diet is not appropriate for everyone.

Micronutrients like vitamin D, zinc, magnesium, and selenium also play roles in immune health, DNA repair, and inflammation regulation. Many cancer patients are deficient, though high-dose supplementation without medical supervision is not recommended. A registered dietitian trained in oncology nutrition can provide individualized support.

Ultimately, the goal is to nourish the whole person, not just restrict or supplement. Good nutrition during treatment builds resilience, improves mood and energy, and may even help enhance long-term survival.

Combining Diet and Exercise: Synergistic Benefits

While diet and exercise each contribute powerfully to cancer prevention and recovery on their own, their combined effect is even more compelling. Numerous studies show that people who adopt both healthy eating and regular physical activity have significantly greater reductions in cancer risk and recurrence than those who focus on just one behavior.

A 2018 study published in JAMA Oncology found that breast cancer survivors who met both dietary and physical activity guidelines had a 42% lower risk of death from all causes compared to those who met neither. Similar findings have emerged in colon cancer survivors, where lifestyle adherence predicts both disease-free survival and overall survival.

This synergy is partly due to complementary biological effects. Exercise improves insulin sensitivity, reduces inflammation, enhances circulation, and mobilizes immune cells. Diet provides the nutrients, phytochemicals, and microbiome support that further reduce oxidative stress and regulate hormones. Together, they reshape the body’s internal terrain—what some researchers call the metabolic and immunological ecosystem—in ways that discourage cancer from gaining a foothold.

Beyond the biology, combined lifestyle interventions also help patients reclaim agency. When cancer disrupts life, diet and exercise can be areas where people feel empowered to act—supporting not just physical healing, but psychological resilience. Programs such as the “Lifestyle Medicine” initiative at MD Anderson, or survivorship clinics at institutions like UCSF and Dana-Farber, provide integrated support that combines nutrition, movement, stress reduction, and social connection for lasting change.

Challenges and Controversies: Where the Evidence Is Still Evolving

Despite strong evidence supporting lifestyle interventions, some areas remain controversial or unresolved. Nutrition and exercise science are inherently complex—human biology is diverse, and long-term trials are difficult and expensive to conduct. As such, not all questions have definitive answers.

For example, the role of soy in breast cancer has sparked debate for years. While soy contains phytoestrogens that mimic estrogen, studies now show that moderate soy intake—especially from whole foods like tofu, tempeh, and edamame—is safe and even protective, particularly in Asian populations with lifelong exposure. However, confusion persists due to earlier lab studies and exaggerated media headlines.

Similarly, supplement use raises questions. While certain nutrients like vitamin D, selenium, and omega-3s show promise in observational studies, high-dose supplementation can sometimes be harmful. The SELECT trial, for example, found that vitamin E supplementation actually increased prostate cancer risk in some men. Whole food sources remain the preferred method of nutrient delivery unless clinically indicated.

Another area under investigation is the ketogenic diet, which may slow growth in certain cancers by restricting glucose, but may be contraindicated in others or in patients with cachexia. Likewise, fasting during chemotherapy is promising in animal models but must be used cautiously in vulnerable patients.

Exercise guidelines, too, are still being refined. How much is enough? What kind is best—resistance training, aerobic, or yoga? Personalized exercise prescriptions are the future, but most oncologists do not yet receive training in this area.

Finally, it is important to acknowledge that lifestyle is not a guarantee. Healthy, active individuals still get cancer. Lifestyle is a modulator, not a magic shield. The key is to avoid both overhype and fatalism, focusing instead on realistic, empowering action.

Special Populations and Health Equity Considerations

While lifestyle interventions hold enormous promise, not everyone has equal access to healthy food, safe spaces to exercise, or integrative care. Cancer risk and outcomes are shaped not just by individual behavior but by the social determinants of health—the conditions in which people are born, live, work, and age.

For example, lower-income neighborhoods often have limited access to fresh produce, clean parks, or walkable streets. People working multiple jobs may lack time or energy to cook or exercise. Racial and ethnic minorities face systemic barriers in healthcare access, insurance coverage, and culturally relevant health education. Studies show that Black and Hispanic populations in the U.S. experience higher rates of cancer-related morbidity and mortality, often linked to disparities in early detection, treatment, and preventive resources.

Cancer prevention efforts must therefore go beyond individual advice and address structural inequities. Promising strategies include:

  • Community gardens and mobile produce trucks in food deserts

  • School-based fitness and nutrition programs

  • Safe streets and green spaces in urban planning

  • Faith-based and culturally tailored interventions

  • Insurance coverage for dietitian services and exercise counseling in cancer care

Health equity is not just a social justice issue—it’s a public health imperative. Empowering everyone to benefit from lifestyle medicine requires policies, environments, and systems that make healthy choices the default.

Practical Guidance: What People Can Do Now

For those who want to take action, the key is not to wait for perfection, but to start where you are. Small, sustainable changes can lead to meaningful benefits over time.

For physical activity:

  • Aim for at least 150 minutes of moderate activity per week, such as brisk walking, dancing, swimming, or cycling.

  • Add strength training 2–3 times per week to preserve muscle and bone health.

  • Break up long periods of sitting with light movement, especially if you work at a desk.

For diet:

  • Fill at least half your plate with colorful fruits and vegetables.

  • Choose whole grains over refined ones.

  • Include legumes, nuts, and seeds regularly.

  • Limit red and processed meats, sugary beverages, and ultra-processed foods.

  • Drink water or herbal teas instead of sugary drinks or excess alcohol.

For cancer patients:

  • Work with an oncology-trained professional

  • Stay active during treatment to the extent that energy and safety allow.

  • Address side effects like nausea or taste changes early to avoid malnutrition.

  • Focus on nutrient density rather than weight loss during active treatment.

Above all, be compassionate with yourself. Lifestyle change is a journey, not a checklist. And even modest improvements can yield measurable benefits in energy, mood, and long-term resilience.

A New Paradigm of Empowerment

Cancer is one of the most complex diseases we face. It involves genes, environment, chance, and time. But amid this complexity, one truth is becoming increasingly clear: lifestyle matters. What we eat, how we move, and how we live our daily lives powerfully influence our risk of developing cancer—and our ability to recover from it.

Exercise and diet are not cures, nor guarantees. But they are among the most effective, least invasive, and most empowering tools available. They work not by targeting the tumor alone, but by cultivating the internal terrain that allows the body to heal, defend, and thrive.

This is a new paradigm—one where patients are not passive recipients of care, but active participants in their healing. And where the choices we make every day are not just routine, but profoundly therapeutic.

The future of cancer care is integrative, personalized, and rooted in science. But it is also human, hopeful, and grounded in something beautifully ordinary: the food we eat, the steps we take, the lives we live.