An Oncologist Explains Why Exercise Is One of the Best Tools Against Cancer

As an oncologist, I spend my days helping patients navigate one of the most difficult diagnoses they will ever face. But increasingly, one of the most powerful recommendations I make has nothing to do with chemotherapy, surgery, or radiation. It involves lacing up a pair of sneakers and going for a walk.

Research consistently shows that regular physical activity can meaningfully reduce the risk of developing several types of cancer, including breast, colon, and endometrial cancers. The evidence is no longer preliminary or suggestive — it is compelling enough that major cancer organizations now include exercise as a core component of their prevention guidelines.

The mechanisms behind this connection are still being studied, but scientists believe exercise helps by reducing chronic inflammation, regulating hormone levels, improving immune function, and lowering insulin resistance. Each of these biological factors plays a role in creating the conditions that allow cancer cells to develop and grow. By keeping them in check, physical activity disrupts that process at a foundational level.

The good news is that you do not need to train for a marathon to see benefits. Studies suggest that even moderate activity — such as brisk walking for 30 minutes most days of the week — can have a measurable impact on cancer risk. Consistency matters far more than intensity, and any movement is better than none.

For patients who have already received a cancer diagnosis, exercise remains highly relevant. Evidence shows that physically active cancer patients often experience fewer treatment side effects, better mental health outcomes, and in some cases improved survival rates. I regularly encourage my patients to stay as active as their condition allows, tailoring recommendations to individual circumstances and treatment stages.

Of course, exercise is not a guarantee against cancer, and I want to be careful not to suggest that people who develop cancer simply did not move enough. Genetics, environment, and other factors play significant roles. But when we look at the tools available to us for lowering risk and improving outcomes, physical activity stands out as one of the most accessible, affordable, and effective options we have.

My message to patients and to anyone concerned about cancer risk is straightforward: start where you are, move more than you did yesterday, and build from there. The science supports it, and as a physician who sees the toll this disease takes every day, I believe it is advice worth taking seriously.