ACSM'S Health & Fitness Journal:
DEPARTMENTS: Fitness Focus Copy-and-Share
Thompson, Dixie L. Ph.D., FACSM
Dixie L. Thompson, Ph.D., FACSM, is the director of the Center for Physical Activity and Health and department head for the Department of Exercise, Sport, and Leisure Studies at the University of Tennessee, Knoxville.
Cancer affects millions of individuals each year. American women have a one in three lifetime risk of developing cancer, whereas the risk for men is nearly one in two. These dire statistics lead to the question: what can be done to lower risk of developing cancer?
CANCER RISK FACTORS
A number of factors influence the development of cancer. As we get older, cancer risk increases. According to the American Cancer Society, more than 75% of cancers occur in people older than 55 years. Other major contributors to cancer development are genetics, environment (e.g., exposure to cancer-causing agents such as asbestos), and lifestyle choices (e.g., smoking and physical inactivity). Although age and genetics make it more likely that certain individuals will develop cancer, these factors clearly do not explain all cancers. It is estimated that one third of the cancer deaths in the United States each year can be attributed to some combination of physical inactivity, poor diet, and obesity. Much current research focuses on the interaction between genetic predisposition and environmental and lifestyle factors. How environmental and lifestyle factors trigger cancer development is a crucial area for researchers.
EXERCISE IN PREVENTING CANCER
The link between cardiovascular disease and regular exercise has been observed for a number of years, but the link between exercise and cancer is more unclear. Part of the reason for this lack of clarity is that cancer entails a wide range of diseases, and factors that may be linked with one type of cancer (e.g., skin cancer) may not be the same as those for another (e.g., colon cancer). A large number of studies have explored the relationship between regular exercise and the development of cancer, and the results are mixed.
The strongest evidence for an exercise-cancer link is with breast cancer and colorectal cancer. Part of the protection provided by exercise may be through weight control, but other independent effects (altering hormones, improving immune system function, speeding movement of foods through the digestive tract, etc.) also are important. There also is evidence that exercise may improve survival rates for individuals battling cancer. The evidence is particularly strong for women fighting breast cancer. Two large studies of women with breast cancer found that those who exercised regularly had a better prognosis than those who were sedentary. It is important to remember, however, that cancer patients should always consult their physicians about all lifestyle choices, including exercise.
GENERAL GUIDELINES FOR NUTRITION AND PHYSICAL ACTIVITY
No set of lifestyle choices can provide complete protection from cancer. However, the American Cancer Society recommends the following nutrition and physical activity guidelines for reducing cancer risk:
* Maintain a healthy weight throughout life through balancing food intake and physical activity.
* Live an active life by engaging in at least 30 minutes of moderate or vigorous activity at least 5 days a week.
* Consume a diet centered on fruits, vegetables, and whole grains and limited in processed and red meats.
* Drink alcohol in moderation, if at all (one or fewer drinks per day for women and two or fewer for men).
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