Some weight-loss programs work because they pre-portion meals for you. Studies show that almost everyone—heavy people and thin ones, nutrition experts and normal folks—underestimates how much they're eating a lot of the time. Instead of buying expensive pre-portioned meals, get acquainted with proper portion sizes so you can help cap overeating. Get started by using a kitchen scale or measuring cups to measure proper servings of your favorite foods. Do this a few times until you can eyeball portions. And try making recipes that offer built-in portion control, like mini meatloaves in muffin tins or casseroles that are easy to divide evenly.