Hunger

According to Jeb on Twitter, Hunger will be added as a new aspect of gameplay to Minecraft. This game mechanic would allow food to be stacked, increasing the amount of food one can carry in their inventory at a time. It has been hinted that this will be added when Hardcore mode is added. Despite that fact, some community modders have already created Single Player mods and Multiplayer mods, both of which incorporate the hunger mechanic.

It will also be added in a "realistic mode", a style of minecraft where you have to drink every 3 days and eat every 7. For more information on "realistic mode", see the link in the links below.

As of 19.07.11 Notch posted pic of the hunger bar on his twitter. The Reallistic mode is may be upcoming in 1.8's update.