I think that our particular culture - always on the run, eating fast empty calories such as cold raw foods (salads, fruits, yogurts, sugar, etc.) trying to stay skinny to fit into the Hollywood image (starving ourselves) along with nutritionless, pesticide covered foods are causing us as a culture to be malnourished. This combined with the many chemicals (fluoride), pollutants and lack of exercise along with getting overchilled by indoor air-conditioning for long periods of time, not to mention wearing too tight and constricting clothing (bras, pantyhose, etc.) that we have been killing off our vitality for years. Perhaps this American lifestyle, polluted environment and conditioned habits mixed with more genetic hypothyroid parents producing more offspring is all adding up.

What I think is at the root of the problem is the paradigm we live in (all yang) and we as a part of nature are just manifesting the results of this type of lifestyle either created or passed down. If we were to change our whole way of being (more yin - equal rest, play and work, let our bodies be their normal healthy size, eating nutritious food and living closer to nature) maybe we would preserve our essence which would increase our immunity. This is easy to say, but like swimming upstream in a fast current to do. I think the real cause of this paradigm we live in is a lack of view of what life is for. The American Indians have the medicine wheel paradigm which was said to believe that the ultimate duty of a life was to have a good lifestyle all to support the spirit so it could do the work it was meant to do here on earth. The Chinese and Ayurvedic medicine have a similar philosophy, with health being an important component of the entire philosophy of life, with the ultimate goal to be the cultivation of the spirit - peace.
I think we as a culture have not developed a paradigm such as this, as we are a young country, but it appears to be taking shape more and more as doctors and natural doctors begin to work together and yoga, tai chi, qigong (chi kung) and healthy foods are all being advocated. I think ultimately, because the people want them.
Excerpt from: Source.