If eating a larger variety in moderation with more plant based and getting more physical activity has been the same health message since Aristotle, what are the 3 biggest barriers to accomplishing health in the US today in your opinion?

If eating a larger variety in moderation with more plant based and getting more physical activity has been the same health message since Aristotle, what are the 3 biggest barriers to accomplishing health in the US today in your opinion? How has your opinion changed since taking this course? What are the biggest barriers to achieving health world wide? How are they different that in the US?