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 .
Association of Energy Intake and Energy Balance with Postmenopausal Breast Cancer in the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial
Energy restriction remains one of the most effective ways known to prevent breast cancer in animal models . However , energy intake has not been consistently associated with risk of breast cancer in humans . In a prospect i ve study , we assessed whether energy intake , body size , and physical activity each independently influence  breast cancer risk in postmenopausal women and estimated the joint effect of combinations of these individual factors . As part of the Prostate , Lung , Colorectal , and Ovarian Cancer Screening Trial , 38,660 women , ages 55 to 74 years and recruited from 10 centers in the United States during 1993 to 2001 , were r and omized to the screening arm of the trial . At baseline , the women completed a self-administered question naire , including a food frequency question naire . During follow-up from 1993 to 2003 , 764 incident breast cancer cases were ascertained . Women in the highest quartile of energy intake ( ≥2,084 kcal/d ) compared with those in the lowest quartile ( < 1,316 kcal/d ) had a significantly increased risk for breast cancer [ multivariate relative risk ( RR ) , 1.25 ; 95 % confidence interval ( 95 % CI ) , 1.02 - 1.53 ; Ptrend continuous = 0.03 ] . Current body mass index ( BMI ) was also positively and significantly associated with risk ( multivariate RR comparing > 30 kg/m2 with < 22.5 kg/m2 , 1.35 ; 95 % CI , 1.06 - 1.70 ; Ptrend = 0.01 ) . Women with ≥4 hours/wk of vigorous recreational physical activity had a significantly reduced risk of breast cancer compared with those who reported no recreational physical activity ( multivariate RR , 0.78 ; 95 % CI , 0.60 - 0.99 ; Ptrend = 0.15 ) . None of these associations with individual energy balance measures was substantially confounded by the other two measures . When we estimated the joint effect of all three variables , women with the most unfavorable energy balance ( the highest energy intake , highest BMI , and least physical activity ) had twice the risk ( RR , 2.10 ; 95 % CI , 1.27 - 3.45 ) of women with the most favorable energy balance ( the lowest energy intake , lowest BMI , and most physical activity ) . Although our estimates of absolute energy intake , based on a food frequency question naire , are imperfect , these results suggest that energy intake , in addition to BMI and physical activity may be independently associated with breast cancer risk . In addition , these three aspects of energy balance may act jointly in determining  breast cancer risk . ( Cancer Epidemiol Prev 2006;15(2):334–41
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 .