Usually, there should be an alarm tone and a text alert when your fasting period starts or ends. 

If you don't receive any notifications, this might have to do with an old Android version. Make sure to upgrade your mobile to the latest Android version.

Furthermore your phone's power saving mode might block the notifications. Please make sure that it is deactivated.

Additionally it might also help to...

+ check if you have another third party security app installed which might block notifications.

+ switch the notifications in the app off and on.

+ go to your systems settings and check if BodyFast has the rights to send notifications (Settings --> Apps --> BodyFast --> notifications).