Fitness may lower breast cancer risk

Aerobic fitness seems to alter the interior workings of cells in ways that may substantially lower the risk of breast cancer.

A new study with female rats found those that were the most fit were much less likely than other animals to develop cancer after exposure to a known carcinogen, even if they did not exercise.

The findings offer tantalizing new clues into the relationship between fitness, exercise and malignancies.

Most of us probably think cardiovascular fitness, which in broad, scientific terms is the ability to get oxygen and energy to muscles, is built with diligent exercise, and the more we work out, the fitter we become. But we would be only about half right. A large percentage of our aerobic fitness, perhaps as much as half, according to some studies, is innate. This genetically determined fitness level varies widely from family to family and person to person. Exercise can augment it, while avoiding movement and gaining weight may reduce it, but a person’s baseline, genetic fitness is his or hers from birth.

In recent years, scientists have become interested in how our innate fitness might affect our overall health, and also why. Many studies have established people with high fitness are at lower risk for a wide range of diseases, including many types of cancer. But whether their disease protection results from regular exercise or from a fortunate genetic heritage — or both — has been unclear.

For the new study, which was published in July in Carcinogenesis, researchers at Colorado State University, Memorial Sloan Kettering Cancer Center in New York City and the University of Michigan opted to focus on breast cancer. Epidemiological studies have shown that being physically fit is associated with lower risk for the disease, but not why.