The Zone Diet was developed by Dr. Barry Sears and has since spawned an entire industry of supplements, books and food. Zone Diet practitioners aim to eat primarily low-fat protein, fruits, vegetables and monosatured fats, thought the diet does make allowances for splurges. Zone Diet meals should include one gram of monosaturated fat per two grams of fat and three grams of low glycemic-load carbohydrates. According to Zone Diet believers, eating meals within this ratio helps balance the body's vital hormones: insulin, eicosanoids and glucagon. Insulin, often a problem for diabetes, can cue the body to store fat, eicosanoids control inflammation, and glucagon regulates the storage and release of carbohydrates and influences blood sugar levels.

There are several guidelines to consider in preparing Zone Diet meals. One key point is to eat the right kinds of fats, proteins and carbohydrates in the right proportions. Recommended proteins include skinless chicken, turkey, fish, and egg whites. Vegetarians interested in the Zone Diet are encouraged to explore the meat-free protein options such as tofu, soy-based meat substitutes, and low-fat dairy products. Dr. Sears' recommends that each meal contain no more protein than can fit in the palm of a person's hand, or approximately 3 to 4 ounces.

Zone-approved carbohydrates to incorporate into meals include all vegetables except corn, which is considered too starchy; oatmeal; barley; and most fruits, excluding raisins and bananas. Cereal, bread, pasta and potatoes are all to be avoided, as these carbohydrates are absorbed more quickly by the body and result in a faster release of hormones into the bloodstream. In a typical Zone meal, approved carbohydrates should make up about two-thirds of the food consumed.

Fat sources eaten by those subscribing to the Zone Diet include almonds, fish oils, olive oils and avocados. Fish oils contain omega-3 fats; the rest of the fats are unsaturated fats. Saturated fats are to be avoided completely. These "bad" fats are found in full-fat dairy products and meats, as well as egg yolks. The fats recommended by the Zone Diet are considered heart-healthy.

Official Zone Diet meals can be delivered to those who want to ensure they are eating correctly. Many different companies specialize in this service. Plans available vary in different cities and regions. Having Zone meals delivered can cost anywhere from $40 to $60 US Dollars (USD) per day depending on what meals are selected. Many of these programs include snacks as well.

The Zone Diet remains a popular eating plan, endorsed by many athletes and celebrities, including actress Lorraine Bracco and actor Mekhi Phifer. Not only is the Zone Diet reported to tell people lose weight, Dr. Sears also claims that his eating plan can help reverse the signs of aging and alleviate high blood pressure, heart disease and diabetes. The diet is also lauded for being easy to follow and encouraging the eating of vegetables and fruits. However, among scientists and nutritionists, opinions about the diet are mixed. Some claim that such restriction of carbohydrates is unnecessary and that the diet includes too much fat. Other critics of the Zone Diet say that Dr. Sears' scientific claims regarding hormones are incorrect.