Hunger

Hunger in The Sims
For obvious reasons, a Sim cannot survive for very long without food. As long as you have a refrigerator, a Sim can enjoy a Snack, Quick Meal, Full Meal or Group Meal (which is the same as a Full Meal except one Sim prepares several servings). If your Sim is lacking a refrigerator for whatever reasons, or because they are unable to cook, he or she can also phone for a pizza. However, eating a pizza is not nearly as fulfilling as cooking a meal, and it can take quite a while for it to arrive. The higher a Sim's Cooking skill is, the better; this enables them to not only prepare food faster and more efficiently, the food they make also fills up the Hunger meter more. Also, they have less chance of causing a fire.

Of course, if a Sim's Hunger meter reaches zero, the Sim dies of starvation. Therefore, it is essential that it does not reach zero. Sims will inform you if they are hungry, usually by refusing to do tasks, or becoming extremely grumpy. A Sim who goes to work or school hungry will unlikely to do well.

There are different factors that go towards how satisfying a meal is, and therefore how much it fills up the Hunger meter. For example, a better fridge will yield a more satisfying meal, as will the type of cooking implement and the type of preparation surface - a food processor is best, followed by a bare counter, and finally, by the surface of the dishwasher.

Hunger in Pets
Cats and dogs will look for their food bowls when they're hungry. Make sure their bowl is clean and full of fresh food. If it isn't, they'll be forced to go rooting around in the trash.