A fictitious ingredient used in all fast food which causes an intense craving. Each restaurant has its own type. One type usually cannot be substituted for another. This usually leads to eating at different establishments until the specific time frame has passed (Which varies for each individual and flavenoid). Failure to satisfy craving may lead to irrational behavior.
"You're eating fast food again?"
"I can't help it, its the flavenoids"
"You had McDonald's 5 hours ago."
"That's why I am going to Taco Bell"