Zone Diet

Devised by Barry Sears and first introduced in 1995, the Zone Diet was made popular by celebrity dieters like Jennifer Aniston. "Although the diet does seem to work for many who have the willpower to stick with the program, research from Stanford and Tufts Universities have shown that study participants on the Zone fared no better than those on other popular diets including Weight Watchers, Ornish and LEARN, losing between 3.2 and 3.5 pounds in a year. Furthermore, many nutritionists believe that the weight loss experienced on the plan has nothing to do with hormone levels and is, rather, a result of eating fewer calories, carbohydrates and unhealthy fats. But one of the Zone's biggest flaws is that it claims that following the 40-30-30 plan may do a variety of things besides help you lose weight, from decreasing your risk of developing cancer, heart disease and other major ailments to improving athletic performance. Unfortunately, according to experts, there isn't much scientific research beyond the testimonials Sears himself has rounded up over the past decade to back up these claims. That means dieters looking to the Zone as a one-stop solution to all of their health concerns may be sadly disappointed.