Cannibal

Cannibal is a perk in Fallout 3, Fallout: New Vegas and Fallout 4 that allows the player character to engage in cannibalism.

Effects
In Fallout: New Vegas, the perk functions the same as it did in Fallout 3, except that it can be acquired much earlier (at level 4 instead of level 12). After consuming 25 corpses, the Courier will acquire the Dine and Dash challenge perk, allowing them to harvest human remains, rather than eat the corpse directly.

The Lone Wanderer and Courier can only eat the corpses of humans and non-feral ghouls. In Old World Blues, the Courier can also eat the corpses trapped inside the Y-17 trauma override harnesses.

Each corpse restores 25 HP, adds 3 rads, and reduces Karma by one point. Each corpse can only be fed from once. If the Lone Wanderer or Courier are caught devouring a corpse, friendly non-player characters (excluding companions) will turn hostile.

Fallout 4
As cannibalism is still such a deplorable act, all companions, with the exception of Strong, Dogmeat, Codsworth, and Gage will dislike the action if they witness it. Hancock, X6-88, Curie, MacCready react negatively, though their affinities are not affected.

The time to consume a corpse is much shorter compared to Fallout 3 and Fallout: New Vegas. The process is also more graphic, with blood spurting out of the corpse.

As of the Survival mode update (1.5.x), Cannibalism has an additional penalty tacked on when in the survival difficulty level. Using it to satisfy the hunger need inflicts the player character with the Dark Craving status effect. Food will no longer sate hunger; the player can only commit cannibalism to fulfill hunger requirements and will go straight from being satisfied to being very hungry instead of the intermediate statuses (peckish, etc). The game treats this as an addiction, which can be cured by any doctor NPC for 75 caps. This will appear as a dialog option. Addictol or refreshing beverage will not cure the addiction.

Dialogue
Nearly all companions will react to The Sole survivor eating human, ghoul or super mutant flesh.