What you may have heard
You may have heard that being inactive or doing very little exercise can increase cancer risk. Studies have shown that not moving enough, especially alongside other lifestyle factors, can raise the chance of developing certain cancers.
What science tells us
Cancer authorities note that physical inactivity is a preventable risk factor for various cancers. It disrupts hormone regulation, increases inflammation, and reduces immune function (all of which can promote cancer development). Conversely, regular physical activity is clearly protective (NCI) (PubMed).
Epidemiological Evidence
- A study published in 2023 showed that individuals with high total physical activity (≥ 8,000 MET-minutes/week) had reduced risks, 10.3% lower for breast cancer, 7.1% lower for colon cancer, 17.1% lower for liver cancer, and smaller reductions for lung and gastric cancers compared to those with low activity. (PubMed)
- A meta-analysis spanning 19 reviews and hundreds of studies found strong evidence that higher physical activity is associated with lower risk of colon cancer and highly suggestive evidence for breast cancer. Evidence was also suggestive for endometrial, lung, esophageal, pancreatic, and meningioma cancers. (PubMed)
- Another meta-analysis revealed that sedentary behavior at work was linked to a 15.5% higher risk of breast cancer. (PubMed)
Laboratory Evidence / Supporting Evidence
Review articles detail how inactivity leads to higher levels of sex hormones, insulin resistance, chronic inflammation, and reduced immunity, which are mechanisms that contribute to cancer risk (PubMed).
IARC Carcinogen Classification
IARC has not classified “physical inactivity” per se as a carcinogen. However, strong epidemiologic evidence places activity as protective against several cancer types, and many cancer agencies recognize physical inactivity as a modifiable risk factor.
How to reduce your risk
- Aim for at least 150 to 300 minutes of moderate-intensity activity per week (about 30–60 minutes most days), or 75 to 100 minutes of vigorous exercise weekly.
- Include strength training two days a week and reduce sedentary time by breaking up sitting with light activity.
Bottom line
Strong human evidence shows that being inactive raises the risk for several cancers, especially of the colon, breast, endometrium, and liver. Physical inactivity is widely recognized as a preventable yet significant risk factor for cancer. Increasing activity is an effective prevention strategy.
To learn about how exercise can lower cancer risk, watch this short video from the Dana-Farber Cancer Institute.
Do you have to go to a gym to exercise? How can you fit regular exercise into your daily life? Check out these short animations from Cancer Research UK andthe World Cancer Research Fund.