Some fat-free foods, like plain yogurt and skim milk, are healthier. But often, fat-free products contain added sugar or corn syrup. Many also have chemical additives to make up for the missing fat. You need fat in your diet, for energy and to help you absorb vitamins. Avoid saturated and trans fats. But don't fear the healthy kind from nuts, seeds, avocados, and fish like salmon and sardines.