Zone Diet: The Zone diet is a weight loss plan based upon the idea that the right ratio of carbohydrates to proteins and fats can control levels of insulin in the bloodstream. Too much of the hormone, according to the diet's developer Barry Sears, PhD, can increase fat storage and inflammation in the body.
In his book The Zone, Sears writes that metabolism can be best regulated with a diet of 40% carbohydrates, 30% protein, and 30% fat. This idea is now widely known as the 40-30-30 plan. The diet does not prohibit any foods, but severely restricts those high in fat and carbohydrates. Fruits and vegetables are the preferred source of carbohydrates in the Zone diet. Protein is limited to low-fat portions that are no bigger and no thicker than the palm of the hand. Monounsaturated fats such as olive oil, canola oil, almonds, macadamia nuts, and avocados are recommended.
The American Heart Association (AHA) classifies the Zone as a high-protein diet and has issued an official recommendation warning against such programs. The AHA statement says high-protein diets have not been proven effective for long-term weight loss and could actually be hazardous to health because they restrict intake of essential vitamins and minerals . On the other hand, the American Dietetic Association (ADA) rates The Zone more moderately and suggests that it is closer to dieticians' recommendations than some other high-protein diets.