p 198 ff in World Cancer Research Fund / American Institute for Cancer Research. Food Nutrition Physical Activity and the Prevention of Cancer: a Global Perspective. Washington DC: AICR 2007; www.dietandcancerreport.org/cancerresourcecenter/downloads/SecondExpertReportfull.pdf “Physical activity is any form of movement using skeletal muscles. Until very recently in history people necessarily engaged in regular moderate and at least occasional vigorous physical activity. However with urbanisation and industrialisation general levels of physical activity have declined. Machines now do most of the work previously done by hand; driving and using public transport have largely replaced walking and cycling. While people in higher income countries and in urban settings in most countries may engage in some active forms of recreation they remain largely inactive and many spend much time in sedentary recreations such as watching television and using home computers. In general the Panel judges that the evidence on physical activity and the risk of cancer which has continued to accumulate since the early 1990s shows or suggests that regular sustained physical activity protects against cancers of some sites. These include colon cancer and female hormone-related cancers independently of other factors such as body fatness. The Panel judges as follows. The evidence that physical activity protects against colon cancer is convincing. Physical activity probably protects against postmenopausal breast cancer; the evidence suggesting that it protects against premenopausal breast cancer is limited. Physical activity probably protects against cancer of the endometrium. The evidence suggesting that physical activity protects against cancers of the lung and pancreas is limited. The Panel is impressed by the overall consistency of the evidence and concludes that relatively high levels of physical activity protect or may protect against cancers of the colon breast (postmenopause) and endometrium. To prevent these cancers the overall evidence supports the message that the more physically active people are the better; however this excludes extreme levels of activity. The Panel also agrees that since physical activity protects against overweight weight gain and obesity it also protects against cancers for which the risk is increased by these factors (see Chapter 8). The evidence assembled for this Report gives an account of the beneficial effects of higher compared to lower levels of physical activity. However the Panel further agrees that the evidence can equally be interpreted as showing that sedentary ways of life increase or may increase the risk of these cancers. Most people in urbanised industrialised CHAPTER 5 and mechanised settings throughout the world now lead these sedentary ways of life. Finally the Panel agrees that the evidence assembled and judged in this chapter supports the general hypothesis that people have evolved and adapted to be physically active throughout life. The Panel also agrees therefore that sedentary ways of life are unhealthy. It is aware of current trends and also projections (summarised in Chapter 1) showing that average physical activity levels are continuing to decrease throughout the world. Within the remit of this Report the strongest evidence corresponding to judgements of ‘convincing” and ‘probable” shows that physical activity of all types protects against cancers of the colon and also of the breast (postmenopause) and endometrium. This chapter does not address the social or environmental (or underlying and basic) determinants of physical activity and its general decline; this is the subject of an associated report to be published in late 2008. ” ; ;
