Physical Activity and Cancer Prevention

Defining physical activity

Physical activity is defined as any movement that uses skeletal muscles and requires more energy than resting. 

Physical activity can be divided into  types: 

1) Total physical activity, which is all types of physical activity including recreational, occupational and transport (walking or biking to work). 

2) Recreational, which encompasses planned exercise, sports and other forms of physical training. 

3) Occupational, which is any physical activity at work. This can vary from sedentary to light, moderate or vigorous physical activity. 

The important concept is that all movement counts as physical activity. Movement can be incorporated into everyday life: shopping for groceries, mowing the lawn, gardening, walking or biking to work, cooking, parking far away from the front door of a store, taking the stairs and not the elevator, the possibilities are endless. A recent study looked at the way older adults sit and how sitting too much might contribute to heart disease and diabetes. What they found is that the average older adult spends between 56% and 86% of their waking hours sedentary. They also found that adults with a prolonged sitting pattern (sitting for hours at a time without getting up) had larger waistlines, higher BMI and their blood work showed more bad fats and higher levels of blood sugar. When those prolonged patterns were interrupted every 20-30 minutes for 2-5 minutes by walking, stretching or simple resistance exercises blood sugars and fats improved. A study looking at over 6,000 women aged 65-99 found that the group with the most prolonged sitting pattern had the highest rate of diabetes.  The bottom-line, get up and move every 30 minutes if you have to sit at a desk.

The benefits of regular exercise

The benefits of regular exercise and over all increased movement include substantial protection against heart attack, stroke, high blood pressure, diabetes, obesity, osteoporosis, depression, dementia (exercise is one of the best ways to protect against dementia), aging and cancer. 

Let's focus on cancer

Physical activity has an effect on many body systems including endocrinologic, immunologic and metabolic processes, which in turn can affect the risk for the development of several cancers. Being physically active also helps to maintain a healthy weight, which can protect against cancer. Physical activity and cancer protection have multiple mechanisms including enhancement of the immune system, improving insulin sensitivity, lowering IGF- 1, and generally improving metabolic profile which has a strong influence on cancer development. In the third Expert Report on Diet, Nutrition, Physical Activity and Cancer the World Cancer Research Fund reports that physical activity convincingly decreases the risk of colorectal cancer. They also report that physical activity probably decreases the risk of postmenopausal breast cancer and endometrial cancer. Limited evidence suggests that physical activity can decrease the risk of developing esophageal, lung, liver and premenopausal breast cancer.

In addition to having a role in the primary prevention of cancer, there is increasing evidence for the potential for physical activity to influence cancer related outcomes and survival. Multiple studies in breast cancer survivors have shown that regular physical activity is associated with decreased risk of breast cancer specific death and all cause death. Similar, promising evidence is also seen with colorectal and prostate cancer.

What is the bottom line?

Be as physically active as possible incorporating as much movement as possible into daily life and limit sedentary time. This can be done as daily exercise (30-60 minutes of moderate activity a minimum of 5 days per week), work, chores, walking or biking to work, playing outside with the kids, taking the stairs. Again the possibilities for incorporating movement into daily life are endless. For all the romantics reading, don't forget about dance. Dance is one of the best activities for physical activity because it incorporates aerobic exercise, complex movement and memorization into one activity. 

REFERENCES

1) Diet, Nutrition, Physical Activity and Cancer: A Global Perspective. World Cancer Research Fund and American Institute for Cancer Research. 2018.