With all the low-fat and fat-free commercial products available, it's tempting to reduce or make substitutions for the sugar and fat in your own recipes to make cookies more healthful. This is risky, because any change in ingredient proportions also changes the texture and flavor of the cookies, and the results may not be what you expect.
Besides adding flavor, sugar and fat make cookies crisp and tender. Reducing sugar and fat makes cookies less crisp and more cakelike. Substituting an artificial sweetener or a lower-fat product will not yield an acceptable cookie.