What happens when I disconnect a service?

Disconnecting a service does not remove your data. This way, you can reconnect the same service again later (handy if you’re trying different fitness trackers!) and we’ll still have your data saved. 

If you have another service that can provide data for the attributes that this service was providing data for, that service will take over. If not, those attributes will be turned off.

For example, imagine you have Fitbit and Garmin connected. You've set the "steps" attribute to come from Fitbit. Once you disconnect Fitbit, steps will now automatically come from Garmin. If you then disconnect Garmin, the steps attribute will be disabled, as it cannot get data from any service.