The Zone Diet’s guru is Dr. Barry Sears, a researcher at M.I.T. The premise of this diet is that you consume calories in a proportion; 40% Crabs, 30% Protein, and 30% Fat at each setting. Ideally it promotes homeostasis and balance. Although sometimes hard to accomplish, getting balance at each meal, with a little planning it is achievable.
Many diet plans are based off this program, including the PR program and Body for Life program made popular by EAS and Bill Phillips. Many bodybuilders follow a similar model, and for the person losing weight it has shown promise, mainly because it is the easiest of the specific diets to follow.
Personally I have had great results with this diet for both myself and my clients. I like the “free” day in the Body for Life book because it gives a day to indulge. Eventually, those indulge days make you sicker and sicker, and you learn to stay with a healthy diet.