Functional medicine refers to the idea that if the various organ systems are performing and interacting with each other properly then you have a healthy, vigorously functioning mind and body

However, if any one system is overburdened and unable to maintain its regulatory action (homeostasis) within the body, then every other system becomes affected in an attempt to compensate. 

Physical symptoms and pathology are a result of eventual decompensation in the organ systems. This is the basis for statements like “treat the whole body” and “treat the cause”. This also explains the concept of “preventive” medicine. Through a process of rational and systematic treatment of the effected organ systems, not only do the current symptoms go away but further dis-ease is prevented.