The most widely accepted definition of good health is that of the World Health Organization Constitution. It states that "health is a state of complete physical, mental and social well-being and not merely the absence of disease or infirmity" (World Health Organization, 1946). In more recent years, this statement has been amplified to include the ability to lead a "socially and economically productive life". The WHO definition is not without criticism, mainly that it is too broad. Some argue that health cannot be defined as a state at all, but must be seen as a process of continuous adjustment to the changing demands of living and of the changing meanings we give to life. It is a dynamic concept. The WHO definition is therefore considered by many as an idealistic goal rather than a realistic proposition. Using the WHO definition classifies 70-95% of people as unhealthy. In spite of the above limitations, the concept of health as defined by WHO is broad and positive in its implications. It sets out a high standard for positive health. It represents the overall goal that nations should strive to reach.
The most solid aspects of wellness that fit firmly in the realm of medicine are environmental health, nutrition, disease prevention, and public health. These are matters that can be investigated and can assist in measuring well-being.