text: special k diet...? what is the speciel k diet..and does it work? how fast do you lose weight...and like how much, really.. you replace two of your meals with one seriving of their cereal. you wont end up losing very much if any. their serving size is so small that you will most likely go hungry soon afterwards which will cause you to eat more. and besides, some of their cereals are loaded with sugar and there are much more alternative foods that you can eat that will be more filling and good for your body.