I've been following a 40/30/30 diet for a very long time now and was curious on Mark's take on Zone diet. I'm disappointed that he seemed to miss a number of key points and wondered if there's a more detailed "primal" take on these issues (I was looking at a Post from 2008).
The major missing piece is the idea of having most meals have a protein to carb ratio somewhere between 0.6 to 1.0, keeping your insulin and Glucagon in an ideal range, leading to further "downstream" hormonal benefits (with most carbs coming from low-glycemic sources). Instead, Mark treats the 40/30/30 ratio as a daily prescription, which is essentially irrelevant (it only really matters per meal.) And Dr. Sears has written a few times on the unsustainability of keeping your body in a ketogenic state--I didn't see any response to that idea.
Mark also thought 30% fat was too low (and likely to make you hungry)--but the 30% fat ratio is clearly stated as a starting point, and the hunger issue just isn't an issue because it's "taken care of" by the hormonal benefits--Sears is all for eating as much monounsaturated fat as you need to supply energy (once you get to desire % body weight).
In any case, my dubiousness was aroused by the Post on "seasonal eating" ("Nature makes apples bright red to encourage us to eat them at the right time of year"), and the Zone post didn't allay my concerns...