Overall , the current literature supports clearly the dose-response relationship between physical activity and the seven chronic conditions identified .
Moreover , higher levels of physical activity reduce the risk for premature all-cause mortality .
The current Canadian guidelines appear to be appropriate to reduce the risk for the seven chronic conditions identified above and all-cause mortality
This systematic review examines critically the scientific basis for Canada 's Physical Activity Guide for Healthy Active Living for adults .
Particular reference is given to the dose-response relationship between physical activity and premature all-cause mortality and seven chronic diseases ( cardiovascular disease , stroke , hypertension , colon cancer , breast cancer , type 2 diabetes ( diabetes mellitus ) and osteoporosis ) .
The strength of the relationship between physical activity and specific health outcomes is evaluated critically .
Leisure-time physical activity, body size, and colon cancer in women. Nurses' Health Study Research Group.
BACKGROUND Physical inactivity and high body mass index ( weight in kilograms divided by height in square meters ) have been linked to increased risk of  colon cancer .  However , none of the few prospect i ve studies in women has shown a statistically significant reduction in colon cancer incidence or mortality associated with increased leisure-time physical activity . PURPOSE In this prospect i ve study , we asked whether leisure-time physical activity , body mass index , or body fat distribution could significantly influence the risk of colon cancer in women . METHODS The participants in this study were enrolled in the Nurses ' Health Study , which began in 1976 . Every 2 years , the women provided additional personal information and information on medical risk factors and major medical events . The time spent per week at a variety of leisure-time physical activities was determined , and the time spent at each activity was multiplied by its typical energy expenditure , expressed in terms of metabolic equivalents or METs . The result ing values for each woman were added to yield an MET-hours-per-week score . Reported diagnoses of colon cancer were confirmed by review of hospital records and pathology reports . Relative risks and associated 95 % confidence intervals were calculated . RESULTS In multivariate analyses that included body mass index , women who expended more than 21 MET-hours per week on leisure-time physical activity had a relative risk of colon cancer of 0.54 ( 95 % confidence interval [ CI ] = 0.33 - 0.90 ) in comparison with women who expended less than 2 MET-hours per week . Women who had a body mass index greater than 29 kg/m2 had a relative risk of colon cancer of 1.45 ( 95 % CI = 1.02 - 2.07 ) in comparison with women who had a body mass index less than 21 kg/m2 . A tendency toward higher colon cancer risk was observed for increasing waist-to-hip ratio ( relative risk = 1.48 [ 95 % CI = 0.88 - 2.49 ] for comparison of the highest quintile ratio [ > 0.833 ] to the lowest [ < 0.728 ] ) . CONCLUSIONS AND IMPLICATION S The significant inverse association between  leisure-time physical activity  and incidence of colon cancer in women in this study is consistent with what has been found in men . Recommendations to increase physical activity and maintain lean body weight should receive greater emphasis as part of a feasible approach to the prevention of colon cancer
Overall , the current literature supports clearly the dose-response relationship between physical activity and the seven chronic conditions identified .
Moreover , higher levels of physical activity reduce the risk for premature all-cause mortality .
The current Canadian guidelines appear to be appropriate to reduce the risk for the seven chronic conditions identified above and all-cause mortality
This systematic review examines critically the scientific basis for Canada 's Physical Activity Guide for Healthy Active Living for adults .
Particular reference is given to the dose-response relationship between physical activity and premature all-cause mortality and seven chronic diseases ( cardiovascular disease , stroke , hypertension , colon cancer , breast cancer , type 2 diabetes ( diabetes mellitus ) and osteoporosis ) .
The strength of the relationship between physical activity and specific health outcomes is evaluated critically .