The effect is gained when the Sole Survivor feeds upon a corpse to satiate their hunger. Food will no longer sate hunger; the player character can only commit cannibalism to fulfill hunger requirements and will go straight from being satisfied to ravenous instead of the intermediate statuses (peckish, etc.).
The Sole Survivor will stay satisfied for 12 game hours before needing to commit cannibalism again (one normally needs to eat every 6 game hours). One corpse will take the player character from ravenous to well-fed.
This perk seems to ignore the Parasites disease. The game treats this as an addiction, which can be cured by any doctor NPC for 75 caps. This will appear as a dialogue option. Addictol, refreshing beverage, and a radscorpion egg omelette will also cure the addiction.