Hunger



Hunger is an aspect of Minecraft added in the Adventure Update that governs several aspects of gameplay. Instead of directly restoring the player's Health as it did before the Adventure Update, eating food now fills up the Food Bar, which is constantly drained by the player's actions. The Food Bar is located next to the player's Health Bar on the bottom of the screen and is represented by ten shanks.

While the player is sprinting, the Food Bar depletes much faster. One is not able to sprint if his or her food level is or less.

The Food Bar does not drain when playing on Peaceful mode. However, its effects on the player's health level remain, and switching difficulties has no effect on the Food Bar's current level. Thus, if the player changes the difficulty level to Peaceful while his or her Food Bar is empty, it will not restore his or her hunger level and the player will continue to starve while healing.

Certain foods and potions have a chance of poisoning ("Hunger" potion effect) the player upon consumption, which causes his or her Food Bar to deplete faster. Rotten Flesh causes poisoning 80% of the time, and Raw Chicken causes poisoning only 30% of the time. Eating a Spider Eye actually deals the player damage ("Poison" potion effect).

Effects

 * When the Food Bar is at points or above, the player's health will slowly regenerate at a rate of 1 health point every 4 seconds.
 * If the Food Bar is at points or below, then the player will not be able to sprint.
 * When the Food Bar is at, the player's health will deplete at a rate of 1 health point every 4 seconds. On Easy difficulty, the player's health stops dropping at 10 health points, on Normal it stops at 1 health point, and on Hard it keeps draining until the player dies or eats food.

Food poisoning
Food poisoning is an effect induced by eating raw chicken or rotten flesh, which turns the Food Bar a sickly yellow-green and slowly drains food. Rotten flesh has a high chance (80%) to cause food poisoning, and raw chicken has a limited chance to cause it (30%). Raw porkchop and raw beef do not have any chance of giving the player food poisoning.

Behavior
Food poisoning lasts 30 seconds and adds 15.0 to the player's Exhaustion Level over the duration. This is slightly less than (two "shanks"). In peaceful mode, the Food Bar changes color, but does not get drained.

The duration of food poisoning does not stack. So, if the player eats many poisonous foods at once, he or she will only feel the negative effects of the most recent poisonous food, plus the consumption time of each other food. Also, since poisoning is recognized by the game as a potion effect, drinking milk will negate the effect as will a potion, allowing the player to eat potentially poisonous food and drinking milk to fill the bar when no other food is available.

Also, passing through a nether portal in SMP will negate the effect (this does not happen in SSP).

As of 1.9 pre4, green swirls rise around the player to indicate the sickness when he or she is poisoned.

Mechanics
There are four fields in level.dat which are related to hunger:
 * foodLevel ranges from 0 to 20 and is represented by the player's Food Bar. One point equals (half a "shank").
 * foodSaturationLevel is an invisible additional hunger variable that is depleted before main foodLevel value. Eating any food will also add some to this variable. Note that this cannot exceed foodLevel. The Food Bar jitters when this equals 0.
 * foodTickTimer increases with every tick when foodLevel is either greater than 17 or equals zero. When foodTickTimer reaches 80, it resets to zero and then heals or deals one point of damage to the Health Bar, respectively.
 * foodExhaustionLevel ranges from 0.0 to 4.0 and increases with every action the player takes. When the exhaustion level reaches above 4.0, it will be subtracted by 4.0 and subtracts 1 point either from foodSaturationLevel or, if foodSaturationLevel equals zero, from foodLevel.

Exhaustion level increase
''Any action not listed here will not increase exhaustion level. For example, the player can travel several days by boat and the food bar will not decrease.''