Starvation is a physical penalty that will lower both your character's mobility and also, temporarily, his/her mastery of any physical skills. For example, if the starvation penalty is -14% and his/her sword skill level is 42%, the effective skill level is 28%.
If the character's hunger bar is full (green all the way) for a whole day the character will start to starve, taking a 7% physical penalty. Each subsequent day without food will add another 7% to this penalty. When the character starts eating again this penalty will be reduced over time.
Starvation isn't uncommon during the first couple of months of a game, depending on starting season, skills, luck - and any arbitrary, self-imposed rules the player follows. Time-consuming tasks like building your own house may also contribute to the character running out of food.