yeah it's an appetite suppressant.
it works well. however it has severe psychological sides (depression, suicidal ideation, etc) for many
it is a cannabinoid receptor antagonist.
essentially it blocks the receptors that cannabis (marijuana) stimulates which are naturally stimulated by naturally produced cannabinoids (thc-like molecules found in the body) and so instead of giving you the munchies like pot it does the opposite and it severely curbs appetite.
which goes to show like the above poster said if you want to lose weight just eat less.