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In 2001, experts concluded that cancers of the colon, breast (postmenopausal), endometrium (the lining of the uterus), kidney, and esophagus are associated with obesity. Some studies have also reported links between obesity and cancers of the gallbladder, ovaries, and pancreas.
Obesity and physical inactivity may account for 25 to 30 percent of several major cancers—colon, breast (postmenopausal), endometrial, kidney, and cancer of the esophagus.
Preventing weight gain can reduce the risk of many cancers. Experts recommend that people establish habits of healthy eating and physical activity early in life to prevent overweight and obesity. Those who are already overweight or obese are advised to avoid additional weight gain, and to lose weight through a low-calorie diet and exercise. Even a weight loss of only 5 to 10 percent of total weight can provide health benefits.
In 2002, about 41,000 new cases of cancer in the United States were estimated to be due to obesity. This means that about 3.2 percent of all new cancers are linked to obesity. A recent report estimated that, in the United States, 14 percent of deaths from cancer in men and 20 percent of deaths in women were due to overweight and obesity.
Physical Activity
Researchers have established that regular physical activity can improve health by:
- Helping to control weight.
- Maintaining healthy bones, muscles, and joints.
- Reducing the risk of developing high blood pressure and diabetes.
- Promoting psychological well-being.
- Reducing the risk of death from heart disease.
- Reducing the risk of premature death
In addition to these health benefits, researchers are learning that physical activity can also affect the risk of cancer. There is convincing evidence that physical activity is associated with a reduced risk of cancers of the colon and breast. Several studies also have reported links between physical activity and a reduced risk of cancers of the prostate, lung, and lining of the uterus (endometrial cancer). Despite these health benefits, recent studies have shown that more than 50 percent of Americans do not engage in enough regular physical activity.
The Centers for Disease Control and Prevention (CDC) recommend that adults “engage in moderate-intensity physical activity for at least 30 minutes on five or more days of the week,” or “engage in vigorous-intensity physical activity for at least 20 minutes on three or more days of the week”.
How might physical activity affect cancer survivorship?
Research indicates that physical activity after a diagnosis of breast cancer may be beneficial in improving quality of life, reducing fatigue and assisting with energy balance. Both reduced physical activity and the side effects of treatment have been linked to weight gain after a breast cancer diagnosis. One study found that women who exercised moderately (the equivalent of walking 3 to 5 hours per week at an average pace) after a diagnosis of breast cancer had improved survival rates compared with more sedentary women. The benefit was particularly pronounced in women with hormone responsive tumors. Another study found that a home-based physical activity program had a beneficial effect on the fitness and psychological well-being of previously sedentary women who had completed treatment for early-stage through stage II breast cancer. Increasing physical activity may influence insulin and leptin levels and influence breast cancer prognosis. Although there are several promising studies, it is too early to draw any strong conclusions regarding physical activity and breast cancer survival.
Two additional studies have suggested a protective association of physical activity after colon cancer diagnosis and survival. Researchers examined the relationship between levels of physical activity both before and after a diagnosis of colon cancer in two different observational studies. Whereas levels of pre-diagnosis physical activity were not related to survival, participants with higher levels of physical activity post-diagnosis were less likely to have a cancer recurrence and had increased survival. Although these studies suggest protective effects of physical activity, more research is needed to understand what levels of physical activity provide these benefits.
Additional Resources:
Livestrong: Good nutrition, exercise and other healthy behaviors can help your body heal from the physical harm cancer and its treatment may have caused.
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