­The Zone diet burst onto the scene in 1995 when Dr. Barry Sears, published his best-selling book "Enter the Zone" with the help of Bill Lawren. Sears was a researcher of biotechnology at the Massachusetts Institute of Technology before becoming a dieting guru [source: Web MD]. His new approach was revolutionary and easy to understand. His book sold by the millions.

The diet is aptly named. It is based on the idea that eating the right foods in the right ratio will help your body operate within a certain optimal zone. This is achieved by controlling the levels of a certain hormone in your body. The result is better health and better concentration. Another reason for the diet's popularity is the fact that it barely affects the amount of time and money you have to spend preparing meals.

­As far as the Zone diet is concerned, the right ratio of foods is more important than the number of calories you consume. No matter the size of your meal, the ratio of protein, fat and carbs never changes. Once you've mastered the ratio, you'll also know what kind of foods to eat. Luckily, there isn't much that's off limits.

Like any weight loss program, the Zone diet has its fair share of critics. There are those who feel the diet raises some health concerns but the majority of experts out there don't believe it to be harmful. Read on to find out how the Zone diet plan works.