When you enable the Fitbit application, you enable the processing, collection and storage of data for Fitbit’s health and wellness features. Data can come from manual data entry in the Fitbit app, a device you paired with the Fitbit app, and/or services you connected to your Fitbit experience, like third party apps.
The list below illustrates the types of features and data collected for you when you use a Google account with Fitbit. See this list instead if you are a legacy Fitbit account user.
Other Health and Wellness: Heart Rate, Resting Heart Rate, Heart Rate Variability, Breathing Rate, Spo2 (Blood Oxygen) Tracking, Skin Temperature Variation