The answer is Regular and Moderate to High Physical Activity
While generally accepted as good for health, medical professionals have conducted extensive research and recommended that the best way to promote health is to regularly exercising, especially at a moderate and high level physical activity.
This means, simple walking is not going to be enough.
We need to exert our bodies to some extent regular to optimal fitness.
Regular exercise is said to reduce to risk of diabetes, heart problems, various types of cancers etc.