For a low-cost dinner in a hurry, swap traditional meat-based meals for a simple tuna casserole. Tuna is low in calories and fat, packed with satisfying protein, and a single can feeds up to four people. Start with egg noodles, macaroni or virtually any other pasta, then blend in a can or two of tuna. Add a can of creamy soup for flavor, then mix in peas or some of your other favorite veggies to create a balanced meal. Keep your casserole kid-friendly with a crunchy topping made from breadcrumbs, french fried onions, dried noodles or even crushed potato chips. Slide your casserole in the oven until it's hot and bubbling, and serve with a simple side salad.