Why Exercise Works: Scientists Kick the Tires

Readers of the Scientific American's longish piece on what, exactly, exercise does for our bodies will not be surprised to learn that the benefits of regular workouts include reducing the risk of diseases such as cancer and diabetes, but some more patient readers, at least, will be fascinated to discover how it fine tunes the autonomic nervous system, reduces the particle size of low-density lipoprotein (LDL) (the bad cholesterol), pumps up the immune system, shrinks the production of estrogen, increases bone density, and may even make us smarter by boosting the production of chemicals such as brain-derived neurotrophic factor (BDNF).
The bottom line: People who follow the advice of the Department of Health and Human Services Physical Activity Guidelines for Americans, (adults between the ages of 18 and 64 should exercise moderately–such as brisk walking or water aerobics– for at least two hours and 30
minutes or vigorously –running, swimming, or  cycling 10 mph or faster)
for at least an hour and 15 minutes weekly)
live an average of three to seven years longer than couch potatoes.
Read more in the Scientific American.