That is not entirely true. It depends on how you have set your font properties in the first place.
When setting the font for any object that supports it you can choose a specific font such as "Calibri", but sometimes you will see "Calibri (Detail)"
The (Detail) indicates that this is the detail font of the THEME, and changing the theme font should affect all objects using the theme font. The theme supports 2 fonts, Header and Detail.
Note that neither of these supports globally setting the font SIZE.
Jim Dettman (EE MVE)
I guess I should have asked more questions. Not sure why, but I took the question to mean on an existing database. Even so, Ander's point about theme's is correct, however most databases are not set this way if they are already existing.