Here's a well researched article from the NRDC's Staff Blog. It's about the difficulties of being carfree/carlight and the impact this has on the health of Americans.
The lead paragraph:
"Perhaps the single most alarming public health trend in the United States today is the dramatic rise in overweight and obesity, bringing serious risks of heart disease, diabetes and other consequences leading to life impairment and premature death. This is bad enough as it is, but I contend that it is particularly unfortunate that we do not sufficiently recognize the extent to which these trends are caused by environmental factors, particularly the shape of our built environment."