Men who increase their level of physical activity in middle age may be able to lengthen their life spans. In fact, beginning a regular exercise program in your 50s may be as effective as quitting smoking when it comes to reducing your risk for early death.
 
For recent ex-smokers, regular exercise may also double your chances of remaining smoke-free after 12 months.
 
Source: British medical Journal, 338: March 5, 2009