Does the factory reset for apple watch erase all activity history?

Everytime I get a new Iphone and try to pair my watch with the new phone it's just awful. It is not intuitive. Apparently, I have to do a full factory reset on the watch now since I didn't unpair the old phone and watch before I activated the new phone. Now my question is will I lose all the historical data related to my activity? I have backed up my phone so it would seem the data would sync but I want to confirm. I need all the activity data to stay.