Fitbit only gives developers access to Daily Totals, thus we have to save one value per day to Apple Health and we choose to save it at the start of the day.
Due to the way Fitbit lets developers access Sleep data, a separate app is necessary to sync every nap, snooze, siesta, etc quickly and accurately.
Fitness Sync for Fitbit to Apple Health is designed for use with the Fitbit platform.
Check out Full Sleep Sync for Fitbit to Health.
Check out Body Sync for Fitbit to Health.
Fitbit creates a mess of garbage data in between your actual Body Weight Logs in order to fill in the gaps.
To avoid this unwanted data, we have created an app just to Sync Fitbit Body Data.
* All information that is read from Fitbit is immediately put into Apple Health and then discarded.
Fitbit only gives developers access to your Daily Resting Heart Rate.
Apple Health has a priority system for Data Sources.
If you have synced and there is no data showing in Apple Health, please reboot your phone.
* Fitbit only allows 3 years of data to be transferred.
Due to this limitation, only one Heart Rate value Per Day will show in Apple Health.
Fitness Sync is a Data Source, and so is your iPhone, and possibly other apps and devices.