Decades of epidemiologic studies and more recent national health surveys have demonstrated the enormous public health impact of physical inactivity. The escalating sedentary lifestyle in the United States, throughout the Western world, and even in developing countries reflects a global epidemic that warrants greater attention from policy makers, health care professionals, and health care systems. Physical activity is associated with many beneficial physiological adaptations and helps prevent the development of many chronic diseases. It also is a useful adjunct to medication and other treatments for many chronic conditions, including cancer, diabetes, and cardiovascular disease (CVD) (1). While the health benefits of activity are accepted widely, the fact remains that a small percentage of people in the Western world perform even the minimal recommended exercise (2). The following article will comment upon four principles related to physical activity and health: 1) both Western societies and developing countries are too sedentary and obese; 2) both higher fitness and physical activity patterns reduce mortality; 3) physical inactivity carries a heavy economic burden; and 4) health care professionals need to take a more active role in promoting physical activity.
BOTH WESTERN SOCIETIES AND DEVELOPING COUNTRIES ARE TOO SEDENTARY AND OBESE
Obesity and a sedentary lifestyle represent escalating national and global epidemics that warrant increased attention by all health care professionals and those responsible for health care policy. Currently, approximately two thirds of people in the United States are either overweight or obese (3). While the United States commonly is thought to lead the world in the rate of increase in obesity, it actually falls into the mid-range of overweight/obesity of countries in the European Community (4). The prevalence of obesity has roughly doubled over the last two decades, and this increase has been paralleled by an increase in the prevalence of diabetes (5). Whether the increase in obesity is attributable to higher caloric intake or to lower physical activity has been the topic of a great deal of discussion, but societal changes make a compelling argument for both causes.
An underappreciated fact is that the largest projected increase in mortality due to chronic diseases (mainly CVD) will occur in developing countries over the next two decades (6). In the largest of the developing countries (China, Brazil, and India), the prevalence of physical inactivity is 60% to 80%, similar to that in the United States (6-9). The World Health Organization (WHO) estimates that the prevalence of physical inactivity accounts for 22% of CVD prevalence globally (2). The increasing numbers of people who smoke, consume unhealthy diets, and are physically inactive are of particular concern in developingcountries. Changing economics and "Westernization" of these countries has brought major shifts in the burden ofdisease from infectious to those of "modern civilization." These include chronic diseases such as CVD, which remains the largest cause of death globally (10). While evidence exists that intervention strategies are effective in reducing chronic disease risk in developing countries (11), undoubtedly fewer resources are available than are needed in these countries to make an impact upon what WHO has termed one of the most serious public health challenges of the 21st century.
BOTH HIGHER FITNESS AND PHYSICAL ACTIVITY PATTERN REDUCE MORTALITY
There is impressive and convincing epidemiologic evidence, accumulated over the past five decades, that the previously mentioned diseases of modern civilization are reduced among individuals who are more physically active. The association between exercise and health has met and surpassed the scientific test of replication; in just the last 5 yr, data from at least 25 ongoing follow-up studies from 12 countries (including developing countries) have been published that further establish the relationship between greater physical activity patterns, higher fitness, and lower morbidity and mortality from cardiovascular and all causes. A concept that remains largely unappreciated by the medical community is that relatively small investments in fitness or activity result in large health outcome benefits. For example, after adjustment for age and other risk factors, each 1-MET increment in fitness yields a 10% to 30% reduction in mortality risk, and meeting the minimal recommendation for activity (30 min of moderate exercise most days of the week) is associated with 20% to 40% reductions in risk (12). Physical fitness is a stronger predictor of health outcomes than physical activity pattern (13,14), likely because fitness is a more objective measure and because fitness includes an important genetic component (13). However, increasing physical activity is the common denominator for the clinical treatment of low fitness, excess weight, reduction in risk for numerous chronic diseases, and premature mortality (1).
THE ECONOMIC BURDEN OF PHYSICAL INACTIVITY
Physical inactivity and obesity are responsible for an enormous portion of chronic disease. Estimates vary, but their combination is responsible for at least 500,000 premature deaths and in excess of $100 billion in health care costs annually in the United States (15-17). Developing countries are following the lead of the United States in terms of the burden of physical inactivity on health. Recent analyses byWHO and the U.S. Centers for Disease Control and Prevention have underscored a growing recognition that the economic impact of physical inactivity is worldwide. Moreover, a joint report by the World Heart Federation and WHO suggests that 60% to 85% of the world's population, including developing countries, is not physically active enough to gain health benefits (18). Oldridge (6), from an analysis of the WHO Online Global database, reported that developing countries report considerably more leisure-time physical inactivity (median 56%) than do developed countries (median 36%). Given the proportionately greater populations in developing countries, the increase in the prevalence of obesity worldwide, and the decline in physical activity, the future economic burden in countries such as India and China will pale that of the United States(6,19).
HEALTH CARE PROFESSIONALS NEED TO TAKE A MORE ACTIVE ROLE IN PROMOTING PHYSICAL ACTIVITY
Despite the impact of physical inactivity on health outcomes and health costs, this issue has not received the same attention from health care professionals and health policy makers as other interventions or risk factors. Recent studies suggest that fitness level achieved on an exercise test and patterns of physical activity have a greater impact on mortality, cardiac events, or both than traditional risk markers for cardiovascular disease such as smoking, hypertension, or hyperlipidemia (14,20,21). Despite the well-documented health benefits of modest increments in fitness or physical activity, clinicians have been slow to integrate physical activity into the health care paradigm. Few clinicians recommend or discuss exercise with their patients. In reviewing exercise test results with patients, for example, the importance of exercise capacity generally gets lost in the concern with markers of ischemia (22). In terms of activity counseling, the percentage of patients who report having discussed exercise with their physician ranges from less than 10% to 34% (23,24); this percentage tends to be lower among those who are sedentary or of low socioeconomic status. Although all physicians are no doubt interested in providing the best care for their patients, evidence suggests that physicians who have been trained in counseling or who maintain healthful lifestyles themselves counsel their patients more effectively (25). In addition to time constraints and limited resources, encouraging patients to exercise lacks the financial and other incentives that tend to be associated with other interventions (25). Given the increasing prevalence of sedentary behavior in Western societies, the increase in chronic conditions that parallel sedentary behavior, and the health benefits of modest amounts of activity, the message must be promoted within the medical community that physical activity should be a more integral part of routine patient care.
WHAT SHOULD BE DONE?
Health care professionals must take a greater responsibility to influence patients and the public to become more physically active. Physicians are the most influential source of advice for patients in matters of healthful behaviors (26,27), but all routine health care encounters (with nurses, clinical exercise physiologists, and other health care providers) should include the recommendation for 30 min of moderate physical activity on most days of the week. Employer-based incentives have included reduced health care costs or more vacation time for employees who are more active, and more research should be undertaken to assess their effectiveness. Efforts to return to environments that promote physical activity should be given priority, including physical education in the schools (the California Endowment reported in 2007 that fewer than 20% of schools meet the minimal 20-min-a-day requirement, and only 4-min-a-day involved vigorous activity) (28). Twelve recent studies observed that increasing access to sites for physical activity increases activity participation, with a median effect size of a 26% increase in people exercising at least 3 d every week. In Nebraska, investments in cycling and pedestrian paths were shown to be offset by reductions in health care costs, with a cost-benefit ratio of 3 (29), and there are numerous other examples of the cost-effectiveness of similar community-based efforts. The Task Force on Community Preventive Services (30) promoted six strategies that were proven effective for increasing physical activity: 1) large-scale, intense, highly visible, community-wide campaigns; 2) point-of-decision prompts that encourage people to use the stairs instead of elevators or escalators; 3) physical education programs in schools; 4) social support programs (such as buddy systems and walking groups); 5) individually adapted behavior change programs; and 6) enhanced access to places for physical activity. Most importantly, recognition of the critical role that physical activity plays in the prevention of chronic disease will need to come from policy makers who have the political will necessary to implement these strategies. Each of us-physicians, allied health professionals, and others - can make efforts to persuade policy makers that investments in both proven strategies and further research are critical to better integrate the value of physical activity into the health care paradigm. In the meantime, each of us can invest the extra moment it takes to discuss physical activity with our patients.
1. Pedersen, B.K., and B. Saltin. Evidence for prescribing exercise as therapy in chronic disease. Scand. J. Med. Sci. Sports.
6. Oldridge, N.B. Economic burden of physical inactivity: healthcare costs associated with cardiovascular disease. Euro. J. Cardiovas. Prev. Rehabil.
7. Rastogi, T., M. Vaz, D. Spiegelman, et al. A physical activity and risk of coronary heart disease in India. Int. J. Epidemiol.
8. Monteiro, C.A., W.L. Conde, S.M. Matsudo, V.R. Matsudo, I.M. Bonsenor, and P.A. Lotufo. A descriptive epidemiology of leisure-time physical activity in Brazil, 1996-1997. Rev. Panam. Salud. Publica.
9. Hallal, P.C., M.R. Azevedo, F.F. Reichert, F.V. Siqueira, C.L. Araujo, and C.G. Victora. Who, when and how much? Epidemiology of walking in a middle-income country. Am. J. Prev. Med.
10. Lopez, A., C. Mathers, M. Ezzati, D. Jamison, and C.J. Murray. Global Burden of Disease and Risk Factors.
New York: Oxford University Press and World Bank; 2006, pp. 17-43.
11. McMichael, C., E. Waters, and J. Volmink. Evidence-based public health: what does it offer developing countries? J. Public Health (Oxford)
12. Myers, J. Exercise and fitness. In: Cardiovascular Prevention and Rehabilitation
, J. Perk, P. Mathes, H. Gohlke, et al.
(Eds.). London, 2007, pp.88-98.
13. Blair, S.N., Y. Cheng, and J.S. Holder. Is physical activity or physical fitness more important in defining health benefits? Med. Sci. Sports Exerc.
14. Myers, J., A. Kaykha, S. George, et al. Fitness versus physical activity patterns in predicting mortality in men. Am. J. Med.
15. Finkelstein, E.A., I.C. Fiebelkorn, and G. Wang. State-level estimates of annual medical expenditures attributable to obesity. Obes. Res.
16. Wang, G., M. Pratt, C.A. Macera, Z.J. Zheng, and G. Heath. Physical activity, cardiovascular disease, and medical expenditures in the US. Ann. Behav. Med.
17. Mokdad, A.H., J.S. Marks, D.F. Stroup, and J.L. Gerberding. Actual causes of death in the United States, 2000. JAMA
18. Mackay, J., and G. Mensah. Atlas of Heart Disease and Stroke.
Geneva: World Health Organization, 2004, pp. 34-35.
19. Zhao, W., Y. Zhai, J. Hu, et al. Economic burden of obesity-related chronic diseases in Mainland China. Obes. Re.
Suppl 1:62-67, 2008.
20. Mark, D.B., and M.S. Lauer. The prognostic variable that doesn't get enough respect. Circulation
21. Myers, J., M. Prakash, V. Froelicher, D. Do, S. Partington, and J.E. Atwood. Exercise capacity and mortality among men referred for exercise testing. New Engl. J. Med.
22. Myers, J. Beyond ST-segment displacement: newer diagnostic and prognostic markers from the exercise test. Am. J. Med. Sports
23. Wee, C.C., E.P. McCarthy, R.B. Davis, and R.S. Phillips. Physician counseling about exercise. JAMA
24. Garry, J.P., J.J. Diamond, and T.W. Whitley. Physical activity curricula in medical schools. Acad. Med.
25. McKenna, J., P.J. Naylor, and N. McDowell. Barriers to physical activity promotion by general practitioners and practice nurses. Br. J. Sports Med.
26. Greenlund, K.J., W.H. Giles, N.L. Keenan, J.B. Croft, and G.A. Mensah. Physical advice, patient actions, and health-related quality of life in secondary prevention of stroke through diet and exercise. Stroke
27. Kreuter, M.W., S.G. Chheda, and F.C. Bull. How does physician advice influence patient behavior? Evidence for a priming effect. Arch. Fam. Med.
29. Wang, G., C.A. Macera, B. Scudder-Soucie, T. Schmid, M. Pratt, and D. Buchner. A cost-benefit analysis of physical activity using bike/pedestrian trails. Health Promot. Pract.
30. Increasing physical activity: a report on recommendations of the Task Force on Community Preventive Services. MMWR Recomm. Rep.