What is the single best thing that I could do to improve my health (and which also helps pain)?

This animated video is one of the videos by Dr. Mike Evans which we have incorporated from www.myfavouritemedicine.com
In a similar vein, here is a link to a podcast by Prof. Steven Blair

http://www.abc.net.au/radionational/programs/healthreport/how-exercise-can-change-your-life/4205740