I find the Zone a much easier diet to follow than a ketogenic one, however I tend to lose more muscle. Par Deus has suggested that an isocaloric diet, which is not substantially different than the Zone(Isocaloric = 33% carbs, 33% fat, 33% protein, Zone = 40% carbs, 30% fat, 30% protein) along with periodic refeed days, which are very similar to the carb-up on a CKD, would actually be better than a CKD for maintaining muscle and losing fat.