To control the amount of fat you eat:
Many foods are now fat-free in response to the recommendation to reduce fat in our diets. You may find some of these foods useful, but it is possible to follow a low-fat diet without using them. Fat-free does not mean calorie-free. Fat-free cookies, candies, chips, and frozen treats can still be high in sugar and calories. Some fat-free foods actually have more calories than their regular-fat counterparts. Eat fat-free foods in moderation, as you would other foods.
WebMD Medical Reference from Healthwise