You would change the Body CS in the theme or document defaults. I will be back with more detailed instructions.

Note, Word is a style-based applicaiton and changing fonts through replace (direct formatting) is doomed to failure on major projects.
http://www.addbalance.com/usersguide/styles.htm

Thank you for the cross-posting note. Here is a link: https://answers.microsoft.com/en-us/...2-961ba3eda512