According to a large longitudinal study, being fit early in life was associated with a 42% lower risk of developing nine types of cancer later in life.
Although exercise has previously been linked to a reduced risk of some cancers, long-term and large cohort studies at many cancer sites are lacking.
The new study, published in the British Journal of Sports Medicine, drew on data from more than 1 million Swedish conscripted men aged 16 to 25 who were followed for an average of 33 years from 1968 to 2005. The results showed that good cardiovascular fitness – a person’s ability to engage in sustained aerobic exercise such as running, cycling and swimming – was associated with a 42% reduced risk of lung cancer, a 40% reduced risk of liver cancer and a 39% reduced risk of esophageal cancer.
It is associated with a lower risk of head and neck, stomach, pancreatic, intestinal, and kidney cancer.
Greater cardiorespiratory fitness appeared to be associated with a 7% increased risk of prostate cancer and a 31% increased risk of skin cancer – although frequent prostate cancer screening and sun exposure may have contributed to these findings.
Lead researcher Dr. Aron Onerup at the University of Gothenburg in Sweden said he was surprised by these broad associations across multiple organ systems and the “consistent association between cardiorespiratory exercise and cancers of the gastrointestinal tract.”
Addressing the unexpected rise in prostate and skin cancers, Onerup said subsequent studies have indicated that men who are more physically fit are more likely to be diagnosed with dangerous prostate cancers.
However, the study “does not fully take into account the effect of diet, alcohol and smoking, which greatly affect the risk of developing cancer”, said Dr Claire Knight, Cancer Research UK’s senior health information manager.
Overall, the results strengthen the motivation to promote interventions aimed at increasing cardiovascular fitness among young people during their school and university years, said Dr Mark Hamer, professor of sports and exercise medicine at University College London.
While other researchers caution against drawing cause-and-effect conclusions from this type of observational study, Hammer added: “This long follow-up period eliminates the problems of reverse causation (pre-existing disease leading to poor fitness and early death) that many previous studies struggle to deal with.”
“Although cardiorespiratory fitness is associated with half of the cancer sites, this is less true for muscle strength. So, although our study did not look at activity, this may indicate that aerobic activities such as running, biking, sports, swimming are more associated with cancer risk than resistance training,” Onerup said.
Reducing cancer risk isn’t the only reason for exercise. There are joint benefits in emotional health and cardiovascular disease prevention. Onerup said, “Some physical activity is better than none, and more physical activity is better for better health outcomes,” and emphasized that it’s never too late to qualify for health care benefits.
Knight recommends 150 minutes of exercise a week. You don’t need to run a marathon or join a gym—just warm up, get a little out of breath, and get your heart pumping.
“Whether you go for a brisk walk, ride a bicycle with a friend, or do chores around the house, these can all be considered ways to be active.”