Adults of average intelligence and beyond are well aware of how to live a healthy physical life - don't smoke, don't drink or do drugs or if you do, do so moderately, eat unprocessed, nutritious foods, exercise -- and yet, much of the population makes several of these unhealthy choices every day.
Seems to me that if human beings made the environment that is their body their top priority, the environment that surrounds their body would not be an issue.