Why Fitness (Not Just How Much You Exercise) Matters in Cancer Risk

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CHICAGO — A person's overall cardiorespiratory fitness is linked to his or her risk of developing precancerous polyps in the colon, which can grow into colon cancer, a new study from Singapore found.

In the study, the researchers found that people with lower levels of cardiorespiratory fitness had a higher risk of developing these polyps, which are also called adenomas.

Doctors have long known that failing to get enough physical activity is linked to an increased risk of colorectal cancer, said lead study author Dr. Vikneswaran Namasivayam, a gastroenterologist at Singapore General Hospital. Namasivayam presented his findings here Monday (May 8) at Digestive Disease Week, a scientific meeting focused on digestive diseases. [7 Cancers You Can Ward Off with Exercise]

In the new study, the researchers focused on precancerous polyps instead of cancer. They wanted to look for a link between fitness and these polyps, because discovering such a link would "lend further credence to the idea" that fitness plays a role in the development of colorectal cancer, Namasivayam said.

The researchers also took things a step further, measuring people's cardiorespiratory fitness and not just asking them how much they exercised, he said.

Cardiorespiratory fitness is a very different concept from physical activity, Namasivayam told Live Science. When people talk about physical activity, the term refers more to a behavior than a biological measurement, Namasivayam said. But cardiorespiratory fitness can be objectively measured, he said.

Another way of looking at the difference between physical activity and cardiorespiratory fitness is that while physical activity influences cardiorespiratory fitness, other factors influence it too, Namasivayam said. A person's age, sex and genetics also affect his or her cardiorespiratory fitness level, he said.

In the study, the researchers measured the cardiorespiratory fitness of 36 adults between ages 45 and 70. Of these participants, 20 people had precancerous polyps and 16 people, the controls, had no polyps.

To determine each person's level of cardiorespiratory fitness, the researchers focused on VO2 max, which is a measure of aerobic fitness that looks at how much oxygen the body is able to use in a given time period to power its cells. The higher an individual's VO2 max is, the more fit that person is. To measure VO2 max, the people in the study were asked to ride stationary bikes to the point of exhaustion, Namasivayam said. [Everything you Need to Know About Aerobic Exercise]

The researchers found that the higher a person's VO2 max was, the less likely it was that a person had a precancerous polyp. In other words, people in the study with precancerous polyps "were more likely to have a lower level of [cardiorespiratory fitness] compared with those who" did not have polyps, Namasivayam said.

The study was small, and more research is needed to help scientists fully understand the link between cardiorespiratory fitness and the risk of precancerous polyps, Namasivayam noted. In addition to replicating the findings of this study, researchers also need to look into the biological mechanisms that could explain the link, he said.

The findings have not yet been published in a peer-reviewed journal.

Originally published on Live Science.

Sara G. Miller
Staff Writer
Sara is a staff writer for Live Science, covering health. She grew up outside of Philadelphia and studied biology at Hamilton College in upstate New York. When she's not writing, she can be found at the library, checking out a big stack of books.