If you eat enough, you will receive the Well Fed bonus. As you become hungrier, your total available stamina will decrease, represented by a dark region inside the stamina bar. Over time, you will become hungry, which will impact your total stamina, as well as your ability to wield most weapons. Here's an excerpt from the official preview of the Survival Mode: Hunger And if you opt into this beta test, you'll be able to try one of the standout offerings of Skyrim's Creation Club - the Survival Mode, a new way to play Skyrim that adds a number of new survival mechanics to the game, like for example hunger, fatigue, and cold, and transforms Skyrim into a much less hospitable place in general. Bethesda's Creation Club has been live in Fallout 4 for a while now, and its Skyrim counterpart is now available on Steam for beta testing.
