The great positive impact of public health programs is widely acknowledged. Due in part to the policies and actions developed through public health, the 20th century registered a decrease in the mortality rates for infants and children and a continual increase in life expectancy in most parts of the world. For example, it is estimated that life expectancy has increased for Americans by thirty years since 1900,[54] and worldwide by six years since 1990.[55]
The environment is often cited as an important factor influencing the health status of individuals. This includes characteristics of the natural environment, the built environment and the social environment. Factors such as clean water and air, adequate housing, and safe communities and roads all have been found to contribute to good health, especially to the health of infants and children.[19][30] Some studies have shown that a lack of neighborhood recreational spaces including natural environment leads to lower levels of personal satisfaction and higher levels of obesity, linked to lower overall health and well being.[31] This suggests that the positive health benefits of natural space in urban neighborhoods should be taken into account in public policy and land use.
The Commonwealth Fund, in its annual survey, "Mirror, Mirror on the Wall", compares the performance of the health care systems in Australia, New Zealand, the United Kingdom, Germany, Canada and the U.S. Its 2007 study found that, although the U.S. system is the most expensive, it consistently under-performs compared to the other countries.[6] One difference between the U.S. and the other countries in the study is that the U.S. is the only country without universal health insurance coverage.
The remaining 45% of health care funding comes from insurance premiums paid by the public, for which companies compete on price, though the variation between the various competing insurers is only about 5%.[citation needed] However, insurance companies are free to sell additional policies to provide coverage beyond the national minimum. These policies do not receive funding from the equalization pool, but cover additional treatments, such as dental procedures and physiotherapy, which are not paid for by the mandatory policy.[citation needed]
In a study in JAMA Internal Medicine, researchers reported that people who ate the most sugar had a higher risk of death from heart disease, even if they weren’t overweight. Another study found that spending just three months on a sugar-heavy diet changed fat metabolism in healthy men, causing them to develop non-alcoholic fatty-liver disease, which boosts the risk of cardiovascular disease.

Just as there was a shift from viewing disease as a state to thinking of it as a process, the same shift happened in definitions of health. Again, the WHO played a leading role when it fostered the development of the health promotion movement in the 1980s. This brought in a new conception of health, not as a state, but in dynamic terms of resiliency, in other words, as "a resource for living". 1984 WHO revised the definition of health defined it as "the extent to which an individual or group is able to realize aspirations and satisfy needs and to change or cope with the environment. Health is a resource for everyday life, not the objective of living; it is a positive concept, emphasizing social and personal resources, as well as physical capacities".[10] Thus, health referred to the ability to maintain homeostasis and recover from insults. Mental, intellectual, emotional and social health referred to a person's ability to handle stress, to acquire skills, to maintain relationships, all of which form resources for resiliency and independent living.[9] This opens up many possibilities for health to be taught, strengthened and learned.