How to change font size in word document produced by R Markdown?

Question

Below is a simple example of a R markdown file, from which I want to produce a word document with font size of 10. I went through different solutions proposed in the forum but none worked. It only worked for html file but not word.

--- 
title: "Title"
output:
    word_document: 
      number_sections: yes
      df_print: paged
fontsize: 10pt
---
# Section
text