Saturation

Saturation is the game mechanic that controls Characters' needs for Food, and is directly tied to Eating, the game mechanic which fills that need. A character with a higher saturation value has eaten recently, and is more full than another character with a low saturation level. You can view saturation of all humans and tamed animals by viewing the "Food" bar and the corresponding mouseover text in the Needs tab.
== General mechanics ==
Saturation is measured in units of nutrition. There are 2 distinct measures of saturation.
* Maximum nutrition, or how much nutrition a pawn can store at any one time. It is dependent on the body size of the species as well as the body size factor and food max factor according to the pawns life stage. The function is species_body_size × body_size_factor × food_max_factor. For adult specimens body size factor and food max factor are both 1. An adult human (with a body size of ) can therefore hold up to nutrition.
** For young humans the formula results in:
*** Baby (0-2 years): × 0.2 × 0.625 = maximum nutrition
*** Child (3-12 years): × 0.35 × 2.286 = maximum nutrition
*** Teenager (13-17 years): × 0.8 × 1.25 = maximum nutrition (therefore same as adults)
** For young insects:
*** Larva: species_body_size × 0.2 × 2 = species_body_size × 0.4
*** Immature: species_body_size × 0.5 × 1.5 = species_body_size × 0.75
** For other young animals:
*** Baby (birds): species_body_size × 0.1 × 6 = species_body_size × 0.6
*** Baby (other): species_body_size × 0.2 × 3 = species_body_size × 0.6
*** Juvenile: species_body_size × 0.5 × 1.5 = species_body_size × 0.75
* Hunger Rate, or how much nutrition a pawn loses per day. Adult baseline humans hunger at a rate of 1.6 nutrition per day. This is determined by species and the Hunger Rate Factor explained below.
In general, humans hunger more than similar animals. An alpaca has the same body size as a human, but only hungers at a rate of 0.44 nutrition per day. A megasloth is four times larger than a human, but hungers at the same rate. Generally, predators hunger slowly - a cougar eats less than half as much as a husky, for instance.
=== Levels of saturation ===
Characters' saturation level is grouped into four thresholds: Fed, Hungry, Ravenously Hungry, and Malnourished. Each threshold exhibits different effects on a character, especially their Thoughts. 
The saturation level boundaries are indicated by small notches on the "Food" bar in the tab of eating pawns.
Label 	Saturation 	Mood modifier(Humans)	Production Rate(Animals)
Fed 	Greater than 25%	(none) 	×100%
Hungry 	12.5% to 25% 	-6 	×50%
Ravenously Hungry	>0% to 12.5% 	-12 	×25%
Malnourished 	0% 	-20 	×0%
Speed of animals' production (wool, milk, eggs or chemfuel) is also dependent on the saturation level, as seen above. Note that production is completely stopped only when 0% saturation; the "malnutrition" ailment does not have a direct impact on animal products.
=== Malnutrition ===
Once a pawn reaches 0% saturation, they will start becoming malnourished. 
When malnourished, pawns gain severity in "malnutrition". Malnutrition is an ailment, with an entirely separate progression to hunger or saturation. When malnourished, malnutrition severity rises by 2% every hour, and once it reaches 100%, the pawn will die. When a pawn is fed, their malnutrition does not immediately go away, though a pawn will no longer gain malnutrition (as Saturation is no longer at 0%). 
For as long as the malnutrition ailment is active, pawns will gain increased hunger. This does not increase the rate of malnutrition severity, just the amount of food eaten after a pawn has been fed. The malnutrition severity decreases at the same rate it increases.
== Saturation changes ==
Saturation goes down every tick (1/2500 of a game hour, or 1/60 a second at level 1 game speed), depending on the character's current saturation and modifiers on their hunger rate.
The following table describes saturation changes of an adult baseline human (100% hunger rate, 1.6 nutrition/day, 1.0 max nutrition):
Saturation 	Threshold range	Change per hour 	Change per day	Game time in stateGame time spent in the state from the upper threshold before crossing the lower threshold, assuming nothing is eaten	Game time since 100% foodGame time spent before entering the state, assuming nothing is eaten and the starting saturation is 100%
Fed 	100% - 25% 	-6.67% 	-160% 	hours 	hours
Hungry 	25% - 12.5% 	-3.33% 	-80% 	hours 	hours
Ravenously Hungry	25% - >0% 	-1.67% 	-40% 	hours 	hours
Malnourished 	0% 	0% Malnourished state does not impact saturation directly. Rather, it increases the "Malnutrition" ailment by 2% per hour, and if this reaches 100%, a pawn dies. This ailment will increase hunger rate of a pawn, but only after they have eaten again.	0% 	50 hours 	hours
From 100% saturation, a human can survive up to 72.5 hours before dying from malnutrition.
Saturation is increased by eating food. For reference, 1 unit of raw food (rice, meat, etc.) gives 0.05 nutrition, or 5% of a human's saturation meter. A simple meal, fine meal, or nutrient paste meal gives 0.9 nutrition, or 90% of a human's meter.
== Hunger Rate Factor ==
The following things will modify hunger rate:
=== Offsets ===
All hunger rate factor offset modifiers stack additively. Once added up, they stack multiplicatively with other modifiers to hunger.
* Stoned on smokeleaf: 
* Go-juice withdrawal: 
* Gut worms: 
* Stomach implants:
** Reprocessor stomach: 
** Nuclear stomach: 
*** Note that the effect of these implants is displayed on the item and hediff info cards as a multiplier (x75% and x25% respectively), but they work like an offset on the actual Hunger rate stat.
* Hypothermic slowdown:
** Moderate: 
** Serious: 
** Extreme: 
* Malnutrition:
** Trivial: 
** Minor, Moderate, Severe and Extreme: 
* Hunger pangs persona trait: 
* Neural supercharger: 
* Bio-starvation (outside of vat): 
=== Multipliers ===
All of these modifiers stack multiplicatively with each other and with the hunger rate factor offsets listed above.
* Gourmand trait: 
* Life stages:
** Human baby: 
** Human child: 
** Human teenager: 
** Insect larva: 
** Insect immature: 
** Other animal baby (including birds): 
** Other animal juvenile: 
* Sleep accelerator: 
* Genetic metabolic efficiency : 
** Positive sum of metabolic efficiency: per point below 0. Min. 
** Negative sum of metabolic efficiency: per point above 0. Max. 
Despite its name and description, the Digestion stat has no impact on hunger rate.
== Overeating ==
Pawns will attempt to eat as their next action once their saturation level reaches 30% to avoid being hungry. Pawns make no effort to avoid "overeating", so any excess nutrition in the food is lost. A default pawn that eats a simple meal (0.9 nutrition) as soon as it is hungry (0.30 saturation) will go to 1.0 saturation and waste up to 0.20 nutrition of food (22% of the meal). In practice, the process of eating takes some time, so not all the food is wasted.
This effect is stronger in animals with lower body sizes - a Labrador retriever with 0.75 body size will get hungry at .1875 saturation and waste .3375 nutrition from the same simple meal. Smaller, more fungible food sources like berries or haygrass (0.05 nutrition) have less of this waste, as the waste will never exceed a single item's worth of nutrition. 
This makes kibble and pemmican particularly useful as feed for smaller sized animals. These foods provide more nutrition than raw food, but will waste far less nutrition than a regular meal would.
== Analysis ==
An adult baseline human will eat roughly 2 simple meals, 32 units of pemmican, or 32 units of raw food per day.
Cooking food effectively "creates" nutrition. A simple meal is worth 0.9 nutrition, but only costs 0.5 nutrition of food to make. This gives simple meals a 180% nutrition efficiency, before the overeating described above.
Due to the low food consumption of animals, as well as the efficiency of meals, it is possible to violate the law of conservation of energy. For example, a female cow produces per day, or nutrition in milk per day. A cow consumes nutrition per day. While cows cannot consume milk, almost all animals can consume meals, no matter what the meal is made out of. So when a cow's milk is turned into nutrient paste meals or even simple meals, it can feed itself with plenty of food to spare. This gets even sillier with chickens, which produce more nutrition in eggs than they consume per day, even before the eggs are cooked. (Note that chickens cannot eat their own eggs, and that they are very prone to overeating.)
=== Conserving food via malnutrition ===
In extreme situations, it may be advisable to stay in a hungry state to benefit from the reduced hunger and in malnourished state to benefit from zero hunger rate at 0% saturation. Note that this requires significant micromanagement to pull off. Forbid the food and unforbid it when pawns are about to fall unconscious.
Consider, for example, a human at 0% saturation and 0% malnutrition. This pawn has 0.9 nutrition (one simple meal) to eat.
If the food is eaten immediately, such human survives:
Hours survived	State
9.75 	Fed
3.75 	Hungry
7.50 	Ravenously hungry
50 	Starving until death from malnutrition
Giving a total of 71 hours alive.
If we instead let the human remain malnourished for 13.75 hours, before eating, the pawn survives:
Hours survived	State
13.75 	Starving up to 27.5% malnutrition (minor)
3.75 	Fed state with 27.5–20% malnutrition (minor)
2.50 	Fed state with 20–15% malnutrition (trivial)
2.50 	Hungry state with 15–10% malnutrition (trivial)
5.00 	Ravenously hungry state with 10–0% malnutrition (trivial)
50 	Starving until death from malnutrition
Giving a total of 77.5 hours alive.
Category:Status Level