The Drug strattera is said to be a norepinephrine reuptake inhibitor and used in the treatment of ADD. i can tell you from first hand experience: that drug totally kills appitite.
fennel seed is supposed to too, many natural remedies are very weak and i dont know how effective it can be
you can get 100,000 MGs (100 Grams) of pure caffeine powder for four dollars at bulknutrition. i just threw that in because i think its funny.