Health app

If you unpair the watch and then re-pair it again you will be asked if you want to setup as new or restore from backup choose restore from backup and you will be given a list of any backups you have in icloud,just choose the most recent one.

You can find backups by following the steps listed here: Locate backups of your iPhone, iPad, and iPod touch - Apple Support

Keeping in mind that restoring from a backup necessarily involves resetting your phone, if you wish to do so, you can follow these steps to do the restore: Restore your iPhone, iPad, or iPod touch from a backup - Apple Support

Only if you have a recent backup you can restore from.