Mark Sisson dissects "The Zone," and precisely so. I respect Barry Sears, and certainly, his prescriptions are far better than, say, those of the attention grabbing low-fat fat-face Ornish (I emphasize: huge understatement).
I tried that diet (Zone) for a couple of months back in the mid-90's when the original book came out. I soon knew it would never work for me. Mark's section on "hunger" is really the essential point.
In the end, it suffers from the same deficit as I think the paleo diet does. Fat is king. It's more than twice as efficient by volume than either protein or carbohydrate, and it's what really makes the difference in dietary success, and I'm thoroughly convinced of that. Fat (animal, coconut –avoid vegetable oils) is what makes the difference between giving in and dialing Pizza Hut, setting off a cascade of diminished-self-image failure, and going in and fixing a cheese omelet cooked in butter.
At least it was for me.
I said "was." Funny thing is, and you may have noticed: I don't blog nearly as much about the wonders of fats. That's because I don't eat nearly as much, anymore. And it was completely natural. Once I reset my genes, over months and months, I've come to now eat far more "normally." I'd call it something, like: "The Intermittent Diet." The key is intermittency in obsession or excess, and moderation. In a sense, scarfing down loads of fat seems, to me, just about as compulsive and unnatural, in the end, as eating an extremely
stupid low-fat diet. But sometimes I eat extremely low fat — over a period of some hours. Just the other night around the campfire, for instance: there were some carrots. So, I munched on carrots to the exclusion of all else. Sometimes I gorge on fruit. Sometimes I gorge on fat. But I don't do any one thing chronically. It can be meal-to-meal, or even day-to-day, but never longer than a few days in a row. And the shift is natural. Once you discover the wonder of Real Food and get out of the processed food crack-house, everything changes (but it takes months). The point is that you can be a true "foodie," as am I, and yet become highly indifferent to any particular dish or any particular meal. You simply look at the whole thing differently, which, I understand mystifies lots of skinny people and gets knowing nods from lots of fat people.
This is key to the whole approach: Primitive man had zero control over the environment. He generally had primary control only over locomotion, which is why they moved around a lot. That's fundamental; and so we have, by modern convenience, removed the most fundamental aspect of primal existence from our quotidian motivation: most of us can easily live in one spot our entire lives. I really wouldn't want it any other way, but the point is that our genes don't know or understand the difference. They are either active (expressed), or dormant. The good news is that we can simulate the stressors and expressers through intermittency. I think that eating in the whole range, from extreme low fat to extreme high fat, within the confines of Real Food, is really the way to go. The constraint implies that the diet is usually going to be of a rather low carb nature (in calories or relatively), and certainly free of most grains, wheat in particular. But the real point is that by switching it up, you fool your genes into "thinking" that you're migrating, experiencing varying bounty along the way. And then they do their job, like they were evolved to do.
In the end, Dr. Sears misnamed his diet. It's far too restrictive, prescriptive as to have the concept of a "zone" applied. "The Range Diet" would have been more apropos, implying a linear range. A diet proscribed by a fully spacial geometry (zone) would of necessity be one of intermittency in multi-variable macro-nutrients, probably with a big edge for animal fats, given their high-value energy efficiency.