When your survivor has eaten their 'Fullness' status will increase making their gathering and movement speed faster. It will also help them use less energy while they sprint. It is very important that you keep an eye on this hunger meter and don't let it get too low. To help stop this from happening you should also keep an eye on your survivors stamina which will deplete over time when you use melee weapons and sprint. Allowing the hunger meter to get dangerously low will make your survivor weak and they will not be able to defent themselves against zombies if attacked.
Whenever you are out and about exploring it should be a priority that you are always collecting and eating scraps of food. Always keep an eye out for Petrol Barrels when you are out exploring as they can be used along with the wood you collect for your outdoors cooking activities. Mastering different types of simple recipes from your time spent at a grill or a bonfire will allow you to cook them at any Petrol Barrels you find. It is advised that you first focus on cooking any dishes that give you the stat boost your survivor needs the most at that moment. Good meals to cook before continuing your travels are those that give you the 'Allay Hunger' boost.
Check out our What are the Food Recipes to find out how to cook meals that give your survivor the 'Allay Hunger' boost.