Compared with physically active people, inactive people develop more health problems, such as heart disease, high blood pressure, diabetes, and depression. People should aim to exercise at a moderate level (for example, walking) for at least 30 minutes on at least 5 days per week or at a vigorous level (for example, running) for at least 20 minutes on at least 3 days per week. Unfortunately, only about one quarter of Americans exercise this much. One way to encourage physical activity may be for doctors and nurses to advise exercise as part of the counseling they routinely provide to patients. To decide whether it is worthwhile to ask doctors and nurses to advise patients about exercise, the USPSTF considered the evidence showing that such advice increases the amount people exercise.