How Intense Exercise May Reduce Your Risk of Cancer

The better your body can generate and sustain high levels of energy during exercise, the lower your risk of developing cancer, researchers are suggesting.

The theory, proposed in an opinion article published in Trends in Cancer, is that some active individuals are predisposed to a higher "energetic capacity," meaning they have a greater ability to produce energy on a sustained basis. A greater capacity for energy means that more energy can be directed toward the immune system’s tasks, resulting in a greater ability to ward off diseases like cancer.

“What we’re saying is that some of us don’t need to train as much as others to gain the benefits (of exercise)," Peter Biro, lead author of the article and associate professor at Deakin University in Australia, tells Verywell. “Our ‘trainability’ can depend on this fixed notion of innate capacity.”

In other words, some people are just lucky. But the authors suggest that energetic capacity can both cause and be caused by high activity levels. What this means is that if you have a naturally high energy capacity, you’re more likely to exercise frequently. Conversely, if you have a naturally low energetic capacity, you can “train” your body to develop a high energetic capacity by increasing your level of physical activity.

Energetic Capacity and Cancer Prevention

The concept of energetic capacity brings a new dynamic to our understanding of exercise and cancer prevention. The main argument presented by the authors of this new article is that energetic capacity determines how well an immune system functions when it needs to fight invaders.

When cancerous cells develop in the body, the immune system is alerted and attempts to contain the threat. But the immune system requires substantial reserves of energy to accomplish this task—similar to a car requiring a full battery for optimum performance. For individuals who have the capacity to generate high levels of energy continuously, the immune system functions better and is able to slow the progression of cancer.

Still, regular exercise cannot completely eliminate your cancer risk.

“In some cases, cancer is linked to genes and heredity,” Ann Harper, cancer exercise specialist and personal trainer, tells Verywell. "If your mother had breast cancer, you are more likely to have breast cancer."

Exercise and Cancer Prevention: What We Know Already

While their emphasis on individual capacity is unique, the Deakin University researchers aren't the first to highlight a link between exercise and cancer prevention. Experts have suggested body weight, hormone levels, and digestion can all be influenced by exercise and play a role in cancer risk.

Obesity

According to the Centers for Disease Control and Prevention (CDC), obesity can increase a person’s chances of developing 13 different cancers, including breast and colon cancers. But with regular exercise, obese individuals can lose weight and reduce their risk of these cancers.

Hormones

Exercise has also been shown to promote proper hormonal balance, something that’s critically important in preventing certain cancers. For instance, breast cancer is linked to unusually high levels estrogen.

Digestion

The cancer-preventing benefits of exercise are also associated with its ability to speed up digestion. When food passes through the gut quickly, the colon has less exposure to carcinogenic substances.

Can Exercise Provide Long-term Protection Against Cancer?

Powering through tough workouts probably only offers a protective effect against cancer as long as you can keep it up.

“Vigorous exercise in one's 20s and 30s may not yield cancer prevention benefits in the elderly years,” Kevin B. Knopf, MD, MPH, an oncologist at Highland Hospital in Oakland, California, tells Verywell. “It helps more to have a lifelong approach to exercise to maintain this favorable response."

Biro agrees that short-term training effects are mostly lost with time. The good news? Any increase in energetic capacity associated with more exercise can keep you moving for the long haul if you're willing to stay motivated. The younger you start, the better.

“An exciting possibility is that we might be able to ‘program’ a higher metabolism in our youth,” Biro says.