If you're wishing to disable your Android phone or connected app on your Google Fit account as an activity tracker you need to "un-allow" the Calorie Cloud app to read your "Step" and "Active Energy" data from Google Fit.
How to disable (this is assuming you have the most updated version of the app):
- Locate & open the "Fit" app on your Android device
- From the main activity screen, select the navigation menu (top left)
- Select "Settings" from the navigation list
- Select "Connected apps" from the list of settings
- Locate and select "Calorie Cloud" on the list of connected apps
- Tap "disconnect" to un-allow the app to receive your data
The next step is to add another tracker. See here how to do that.