Can a guy wear this and would anyone know?

ya i guess you could use it, but i dont think guys should be obsessing about their looks like girls do cuz thats kinda weird and also if u want to look slimmer for a girl or something then u shouldnt do it cuz she is going to be thinking that u are all slim and y and then when u have with her or if she finds out that u wear that some other way then that is going to be embarring ...you shopuld just lose weight naturally or be urself