More expensive refrigerators hold more food. They also add a bonus amount of hunger satisfaction. The more cooking skill you have, the higher the hunger satisfaction. Additionally, hunger is the one need that if left unmet can kill your Sim. To quickly fulfill your Sim's hunger even with low cooking skills, make a meal using Beef, Pork, Lamb, and Potatoes.
If you are low on money and do not have enough to eat, sell your refrigerator, stove, etc. and buy a Fruit Punch Barrel. It will satisfy your hunger about 98%. You can just go to "Drink From Tap" and it will do the rest.