To make your Google Fit display less brightly, you can turn on Dark theme in Google Fit. Dark theme can be easier on your eyes and uses less battery.
Change display to Dark theme
- On your Android device, open the Google Fit app
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- At the bottom, tap Profile
Settings
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- Under 'Display', tap Theme
Tip: You can also choose these modes on Google Fit:- Light: The default display.
- System Default: Google Fit uses the same display as the rest of your device. Learn how to change your display settings.
- Set by Battery Saver: The default display switches to Dark theme when Battery Saver is on. Learn more about Battery Saver on Android.
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Settings 
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