What if there was a prescription your doctor could give you that would lower your risk of heart disease, stroke and most cancers? What if that prescription could also prevent and treat high blood pressure, high cholesterol and diabetes? What if that same prescription could reduce your risk of developing Alzheimer's disease, decrease depression and improve cognitive function and memory better than any other available treatment? Would you be interested in that prescription?

What if that prescription could also help you maintain a healthy body weight, increase your strength and improve your fitness? What if you could get all of these benefits with no negative side effects? Are you interested now?

The prescription isn't a drug or other medical treatment. It is regular physical activity.

Research shows that if you have a low level of physical activity, you are at a greater risk of dying than if you smoke, are obese or have high blood pressure or cholesterol. In fact, physical inactivity is now thought to be the leading cause of preventable deaths in the United States.

If you didn't know this, you are forgiven. Much attention is given to health conditions such as diabetes, high blood pressure, high cholesterol and obesity - with good reason, of course - at the expense of focusing on physical inactivity. This is partly because of the "education" provided by pharmaceutical companies, who develop drugs to treat these conditions and advertise them widely.

But physical inactivity has a huge impact on health, largely because a lack of regular exercise can cause or exacerbate these other diseases. Unfortunately, modern medicine tends to focus medications and surgical procedures, so a low-tech approach, like taking a 30 minute walk every day, is often overlooked.

May is Exercise is Medicine Month, a time for everyone to recognize the valuable health benefits of regular physical activity. Exercise is Medicine is an initiative focused on encouraging physicians and other health care providers to include exercise in health assessment and in treatment plans for all patients. Unfortunately, the benefits of physical activity and exercise recommendations are not emphasized in medical education. The result is that only 34 percent of U.S. adults report having received exercise counseling at their last physician visit.

The amount of exercise needed for health benefits is lower than you might think. The 2008 Physical Guidelines for Americans makes the following recommendations for adults and children.

Adults - 150 minutes of moderate-intensity or 75 minutes of vigorous-intensity aerobic physical activity per week - Strengthening activities that involve all major muscle groups at least two days per week Children - 60 minutes or more of moderate or vigorous physical activity every day - Vigorous-intensity activity at least 3 days per week - Muscle-strengthening and bone-strengthening activity at least 3 days per week

Moderate-intensity physical activity means working hard enough to raise your heart rate and break a sweat, yet still being able to carry on a conversation. Examples include brisk walking, ballroom dancing and yard or house work. Vigorous-intensity physical activity causes rapid breathing and a substantial increase in heart rate. Jogging, aerobic dancing and swimming are examples of vigorous activities. The recommendation for adults can be met by going for a 30-minute brisk walk on five days each week. Additional health benefits come from doing more, either higher intensity exercise or longer duration activity.

The Exercise is Medicine initiative aims to increase physician awareness of the health benefits of exercise, but it will probably be some time before exercise counseling becomes the norm. In the meantime, you should ask your doctor about including exercise in your personal health care plan. Then, go for a walk!

Brian Parr, Ph.D., is an associate professor in the Department of Exercise and Sports Science at USC Aiken where he teaches courses in exercise physiology, nutrition and health behavior. He is a member of the American College of Sports Medicine and is an ACSM certified clinical exercise specialist; his research focuses on physical activity in weight management and the impact of the environment on activity and diet. Parr lives in Aiken with his wife, Laura, and sons Noah, Owen and Simon.