you HAVE to have all three of them as they require all your daily nutrients your body needs to purely function, once your in the joys of blissful ketosis (oh how i love you ketosis) you're body isn't really hungry, its just the cravings most people have to deal with, but you must take all your shakes as this is a VLCD. i treat it are purely medicine, even if it means making it before bed and gulping it down, or making up two shakes at once if you're not hungry. ive done that alot, i went through weeks at a time of no hunger n drinking the shakes was just an action i did, no pleasure gained!! just drink them all!