Cancer remains the second leading cause of death in France. If genetic factors play a role, research confirms that up to 40% of cancers could be avoided through lifestyle changes, of which regular physical activity is one of the best documented levers.
In 2018, the International Agency for Research on Cancer (IARC/IARC) published its findings on the link between physical activity and cancer: the level of evidence is sufficient to state that physical activity reduces the risk of 13 different types of cancer. These conclusions come from the analysis of hundreds of epidemiological studies representing millions of participants.
1. Cancers whose risk is reduced by physical activity
2. Biological mechanisms of protection
The anti-cancer protection of physical activity is not linked to a single mechanism, it is the result of a simultaneous action on several biological processes involved in tumor development:
- ●Reduction of insulin resistance and IGF-1: insulin and insulin-like growth factor 1 (IGF-1) are growth factors that promote cell proliferation, including that of cancer cells. Exercise reduces their circulating levels.
- ●Regulation of sex hormones: for hormone-dependent cancers (breast, endometrial), exercise reduces circulating levels of estrogen, largely by reducing fat mass, the main source of estrogen after menopause.
- ●Reduction of chronic inflammation: chronic low-grade inflammation creates a favorable environment for tumor development. Regular exercise significantly reduces inflammatory markers (CRP, IL-6, TNF-alpha).
- ●Strengthening immune surveillance: NK (Natural Killer) cells and cytotoxic T lymphocytes, responsible for the detection and destruction of abnormal cells, see their activity increase with physical exercise.
- ●Regulation of the microbiota: a diversified microbiota (favored by exercise) is associated with better detection of cancer cells and an improved response to immunotherapies.
- ●Reduction of chronic oxidative stress: regular exercise strengthens endogenous antioxidant defenses, reducing DNA damage that can initiate cancerous transformation.
3. The dose-effect link: how much exercise?
A reference meta-analysis (Moore et al., JAMA Internal Medicine 2016) involving 1.44 million people evaluated the relationship between the amount of physical activity and the risk of 26 types of cancer. His conclusions:
- ●A significant effect at modest levels: even physical activity below WHO recommendations is associated with a measurable reduction in risk for several cancers. The benefit is linear in low to moderate levels.
- ●A plateau effect beyond the recommendations: for most cancers, the benefit stabilizes after 150 to 300 minutes of moderate activity per week. Larger volumes do not provide significant additional reduction.
- ●Moderate intensity is sufficient: Contrary to what one might expect, moderate exercise (brisk walking, cycling, gentle swimming) is almost as effective as vigorous exercise for most cancers.
The practical conclusion: standard WHO recommendations (150 min of moderate activity per week) are sufficient to produce most of the documented anti-cancer protection. No need for extreme practice.
4. Physical activity during and after cancer treatment
Exercise research in patients undergoing treatment or remission is one of the most dynamic areas in oncology. The conclusions are increasingly convincing:- During chemotherapy and radiotherapy: adapted exercise (even modest) reduces treatment-related fatigue, the most debilitating symptom. Randomized studies show a reduction in fatigue of 20 to 30% in physically active patients.
- ●Survival and recurrence: for breast, colon and prostate cancer in particular, prospective studies show a reduction in the risk of recurrence and an improvement in overall survival in active patients after treatment.
- ●Quality of life: exercise significantly improves the quality of life, psychological well-being and functional capacities of oncology patients.
Exercise during and after cancer must be adapted and if possible supervised by a trained professional (sport health on prescription). A regular health check-up, including markers of overall health, is the best primary, secondary and tertiary prevention tool in this area.
5. A message of prevention, no guilt
It is essential to read this data with the appropriate perspective: physical activity reduces the risk of certain cancers, it does not cancel it. Very active people develop cancers, and sedentary people do not develop them. Prevention is a probability, not a guarantee.
This prevention message is not intended to make people with cancer feel guilty, but to provide information on a modifiable risk factor on which everyone has a capacity to act. Moving regularly reduces a risk which, on a population scale, represents tens of thousands of avoidable cases each year in France. 14px;font-weight:700;color:#006064;font-size:1.1rem">💡 Tips to remember
- Regular physical activity reduces the risk by 13 different types of cancer, according to the conclusions of the IARC (2018). This is no longer a hypothesis, it is a solid conclusion from preventive oncology.
- Standard WHO recommendations (150 min of moderate activity per week) are sufficient to produce most of the anti-cancer protection. No need for extreme exercise to benefit from this protection.
- Exercise reduces cancer proliferation by acting on insulin resistance, sex hormones, chronic inflammation and immune surveillance, several complementary mechanisms.
- During chemotherapy, adaptive exercise reduces treatment-related fatigue by 20 to 30%. After treatment, it reduces the risk of recurrence for several cancers.
- A regular health check-up, including inflammatory, metabolic and glycemic markers, is the best primary prevention tool for early identification of modifiable risk factors.
