It’s often difficult to discern what a serving size really looks like. A recent study found that when cereal flakes were crushed up, people poured more into their bowls (by weight), because it didn’t seem to take up very much room. As a result, they ate 25 percent more—72 more calories—than when they were given whole flakes. To easily limit your intake, try buying a breakfast cereal with big flakes and eating out of a modestly sized bowl. And remember that the size-matters principle doesn’t just apply to cereal. Picture, for example, how many more grains of rice will fit in a bowl than cauliflower florets, or leaves of lettuce.