Yes, exercise has all kinds of positive effects, but perhaps the most compelling reason to work out is to avoid the negative. To exercise because you just don't dare not to. The myriad illnesses that exercise helps stave off are just too frightening.
Case in point: Colon cancer. I know two people who died of it in middle age, deaths that included much physical pain and left behind young children. The National Cancer Institute has a colon-cancer risk assessment tool that lets you calculate your personal risk (That's mine to the left. Not nearly as low as I'd hoped.) But before you even get there, the introductory page reminds you:
Factors that can lower your risk of colorectal cancer include:
•colorectal cancer screening
•regular use of aspirin and NSAID’s (which stands for non-steroidal anti-inflammatory drug)
•maintaining a healthy weight
•regular, vigorous exercise (all activities that cause sweating and heavy breathing)
•a diet high in vegetables
•hormone replacement therapy use in women
It also includes "inactive lifestyle" among the factors that heighten your risk:
Factors that can make your risk of colorectal cancer higher include:
•close relatives (parents, brothers, sisters, or children) who have had colorectal cancer
history of colorectal polyps
This program aired on January 30, 2012. The audio for this program is not available.