Physical activity and sedentary behaviour

It is estimated that 5% of cancers in the United States are linked to lack of regular exercise³ or sedentary lifestyle.² Globally, it has been estimated that 135,000 deaths from cancer each year are attributable to physical inactivity.⁵²

Physical activity and sedentary behaviour in Australia

Data from the 2011-12 Australian Health Survey indicate that 60% of Australian adults do less than 30 minutes of exercise per day.⁵³ Around 30% of the adult population reported more than 5 hours of sedentary leisure activity each day.⁵³

Physical activity

The 2007 WCRF and AICR report and tumour-specific updates identified that physical activity protects against certain cancers and also limits weight gain, itself a cause of some cancers.^8-15 There was convincing evidence for the protective effect of physical activity against colon cancer and probable evidence for postmenopausal breast cancer and endometrial cancer.^8-15 Limited suggestive evidence supports a protective effect against premenopausal breast, lung and liver cancers.^8-15 To reduce risk of cancer, the report recommends being physically active as part of everyday life, including at least 30–60 minutes daily, and limiting sedentary habits, such as watching television.⁸

Australia’s Physical Activity and Sedentary Behaviour Guidelines recommend that adults should accumulate 150 to 300 minutes of moderate intensity physical activity or 75 to 150 minutes of vigorous intensity physical activity, or an equivalent combination of both moderate and vigorous activities, each week.⁵⁴ Activity at the upper end of the scale (i.e. 300 minutes of moderate / 150 minutes of vigorous) is required for the prevention of unhealthy weight gain and some cancers.⁵⁴ The guidelines also recommend minimising the amount of time spent in prolonged sitting and to break up long periods of sitting as often as possible.⁵⁴

Sedentary behaviour and cancer

The WCRF and AICR report indicated that there is convincing evidence that sedentary behaviour increases risk of weight gain, overweight and obesity.⁸ Two 2014 meta-analyses reported an association between sedentary behaviour and increased risk of some cancers, including colorectal, endometrial and lung cancers.⁵⁵,⁵⁶ There was inconsistency with results for breast cancer.⁵⁵,⁵⁶

The 2002 IARC Handbook of Cancer Prevention linked decreasing levels of physical activity to increases in overweight and obesity.⁴⁹ The Handbook reported that adiposity (obesity) and inactivity appeared to be the most important, avoidable causes of postmenopausal breast cancer, endometrial cancer, renal-cell cancer, and oesophageal adenocarcinoma, and among the most important avoidable causes of colon cancer.⁴⁹

Cancer Australia recommendations for individuals

Cancer Australia recommends aiming for at least 30 minutes of moderate-intensity physical activity every day and limiting sedentary habits, such as watching television, to reduce cancer risk.

Table 3: Summary of evidence for physical activity and cancer sites

Protective factor	Source	Evidence	Cancer site
Physical activity	WCRF/AICR 2007–20158-15	Convincing	Colon
		Probable	Postmenopausal breast, endometrium
		Limited	Premenopausal breast, lung, liver

See Appendix 1 for explanation of evidence.