What is physical activity?
Physical activity is defined as any movement that uses skeletal muscles and requires more energy than does resting. Physical activity can include working, exercising, performing household chores, and leisure-time activities such as walking, tennis, hiking, bicycling, and swimming.
Physical activity is essential for people to maintain a balance between the number of calories consumed and the number of calories used. Consistently expending fewer calories than are consumed leads to obesity, which scientists have convincingly linked to increased risks of 13 different cancers (1). Additionally, evidence indicates that physical activity may reduce the risks of several cancers through other mechanisms, independent of its effect on obesity.
What is known about the relationship between physical activity and cancer risk?
There is substantial evidence that higher levels of physical activity are linked to lower risks of several cancers (2).
- Colon cancer: Colon cancer is one of the most extensively studied cancers in relation to physical activity (3). A 2009 meta-analysis of 52 epidemiologic studies that examined the association between physical activity and colon cancer risk found that the most physically active individuals had a 24% lower risk of colon cancer than those who were the least physically active (4). A pooled analysis of data on leisure-time physical activity (activities done at an individual’s discretion generally to improve or maintain fitness or health) from 12 prospective U.S. and European cohort studies reported a risk reduction of 16%, when comparing individuals who were most active to those where least active (5). Incidence of both distal colon and proximal colon cancers is lower in people who are more physically active than in those who are less physically active (6, 7). Physical activity is also associated with a decreased risk of colon adenomas (polyps), a type of colon polyp that may develop into colon cancer (8). However, it is less clear whether physical activity is associated with lower risks that polyps that have been removed will come back (9–11).
How might physical activity be linked to reduced risks of cancer?
Exercise has a number of biological effects on the body, some of which have been proposed to explain associations with specific cancers, including:
- Lowering the levels of hormones, such as insulin and estrogen, and of certain growth factors that have been associated with cancer development and progression (23) [breast, colon]
- Helping to prevent obesity and decreasing the harmful effects of obesity, particularly the development of insulin resistance (failure of the body’s cells to respond to insulin)
- Reducing inflammation
- Improving immune system function
- Altering the metabolism of bile acids, resulting in decreased exposure of the gastrointestinal tract to these suspected carcinogens (24, 25) [colon]
- Reducing the amount of time it takes for food to travel through the digestive system, which decreases gastrointestinal tract exposure to possible carcinogens[colon]
Besides physical activity, it is very important to get screened for colon cancer. Contact Brooklyn Borough President Eric Adams’ office, and they will work with you to schedule an appointment for a screening with one of their partner medical centers in Brooklyn. Contact the Borough President’s office at (718) 802-3847.
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