Answer:
Its referring to everyone's wellbeing around you.
Explanation:
Fitness and health have to do with a great part in everyone's physical wellbeing without people wouldn't be healthy and fit. So, this is implying to watch out for those around you's health and physical fitness and to help them if they are struggling with there own, the are everyones business part refers to how everyone should know how to be healthy and physically fit as well as you should be watching out for others well being as well!
