Starvation

Starvation is the state of not having enough to eat. It results from a deficit of Supplies for the local troops. A random selection of units is not fed each month, with a total Supply Size generally equivalent to the amount of unmet Supply Usage.

Those who have had to go without eating are Starving; they suffer -4 Morale and have a 5% chance to get Diseased each turn, until they get to a province with a Supply surplus. It's certainly possible for a unit to not get to eat while already suffering from malnutrition; Starving while already having the Starving trait "upgrades" their chance of Disease to 50%.

Units with a Terrain Survival trait in a matching province can attempt to forage for food, if they draw the short straw; they have a 50% chance to not Starve when they're not fed, and a separate 50% chance to avoid Disease if they'd otherwise get it.