Fitness Helper is multiuser application, so use user profiles to store user data. Every user can have own profile. Every user profile store personal data like:
New user creating is possible when program is running (if user profile count = 0) or when application is started after click "File > Create user" menu. User selecting is possible when program is running (if user profile count > 1) or when application is started after click "File > Change user" menu. User removing is possible when application is started after click "File > Change user" menu and click "-" (minus) button.