This higher-protein, lower-carbohydrate diet is supposed to decrease hunger, then weight.

An exact meal plan based upon each person's gender, activity level and current percentage of body fat is designed to include 40 percent of its calories from carbohydrates, 30 from protein and 30 from fat. All meals and snacks follow this 40-30-30 distribution ratio, causing the body to work within its peak performance "zone" for maximum energy and weight loss.

• Rapid weight loss without severe calorie restriction.
  
  
• Enjoyable for meat eaters, with roast beef and steaks included.
  
  
• Some specific meal plans ease some of the complexity of the Zone and the different phases of the diet plan.

• The 40-30-30 ratio for every meal and snack can be difficult to attain.
  
  
• Very low carbohydrates means very low energy levels.
  
  
• Also low in some vitamins and minerals.
  
  
• Low-fiber diet may increase constipation .