According to the 2008 Physical Activity Guidelines for Americans, (1) being physically active on a regular basis

• Improves your chances of living longer and living healthier
• Helps protect you from developing heart disease and stroke or its precursors, high blood pressure and undesirable blood lipid patterns
• Helps protect you from developing certain cancers, including colon and breast cancer, and possibly lung and endometrial (uterine lining) cancer
• Helps prevent type 2 diabetes (what was once called adult-onset diabetes) and metabolic syndrome (a constellation of risk factors that increases the chances of developing heart disease and diabetes; read more about simple steps to prevent diabetes)
• Helps prevent the insidious loss of bone known as osteoporosis
• Reduces the risk of falling and improves cognitive function among older adults
• Relieves symptoms of depression and anxiety and improves mood
• Prevents weight gain, promotes weight loss (when combined with a lower-calorie diet), and helps keep weight off after weight loss
• Improves heart-lung and muscle fitness
• Improves sleep