This project has moved to Planet Minecraft.
This data pack encourages players to consume a variety of food. Each type of food can be consumed a certain number of times before it becomes unpalatable (you'll get a warning of hunger, but if you persist in eating the same thing, you'll suffer poison). Each time you eat any food, the consumption count of all other food items goes down, allowing you to consume them more times. This means that you'll need to switch between food items each time one becomes unpalatable, but eventually be able to return to previous food items you've eaten. When you consume a food item that has counted all the way back down to 0 (the default state of something you haven't eaten), eating that food item will give you absorption.
Foods you've eaten recently, and whether a food has become poisonous, are displayed in the Advancements under a dedicated advancement tab.
The severity of the hunger, poison, and absorption you receive from this data pack is influenced by the difficulty you've set; peaceful and easy have less effect than normal and hard difficulties.
More information about data packs and how to use them can be found on the official Minecraft Wiki.