https://ringofbrodgar.com/wiki/Find_food!
Food has two separate and often competing or contradictory functions.
1. Give you Energy to perform various actions without starving.
2. Give you FEPs that cause one your Attributes to increase when your FEP bar is filled.
Following foods should help you not starve and also allow some FEP gain.
https://ringofbrodgar.com/wiki/Grilled_Frog_Legs frogs can be found primarily in swamps, but also in forest terrain during dawn and dusk (verify)
https://ringofbrodgar.com/wiki/Mushroom_Spit mushrooms can be found on all forest terrains once you have sufficient perception*exploration
Every time you eat something, your hunger bar fills up. This is misleading, and the entire system would be better if simply renamed "appetite."
You start at empty 300% efficiency bar, meaning all FEPs are tripled when eating. (You will slowly decay back there over time passively without need to be logged in.) Once you fill up the bar, you move on to 200% bar for double the base FEPs. This bar decays faster than the first. Following bars are 100% and 50% efficiency, and decay even faster.
Most advanced players agree that it's best to stay in the 300% bar, but this might require large amounts of Salt that is often contested Localized Resource.
If you have traded or scavenged high quality tools it might be easy to reach a situation where it's feasible to make foods that one-shot your 200% bar, at least until your attributes rise enough.
(I've probably strayed bit too far from the purpose of the page, which is to help new player to not starve.)