The Zone Diet is based on the premise that achieving "hormonal balance" through eating ideal ratios of carbohydrates, proteins, and fats at every meal and snack is the most effective way to help the body digest and properly utilize ingested foods. The diet was developed and popularized by a biochemist, Barry Sears Ph.D. who refers to this optimal functioning as being "in the zone." This is what led to his diet program being called the "Zone Diet."

Sears is of the opinion that being "in the zone" boosts overall energy levels while also increasing both mental and physical performance. Ultimately, Sears says the Zone Diet helps to fight aging-related problems, prevents chronic cardiovascular diseases, and promotes effective and long-term fat burning.

How the Zone Diet Works

The idea behind the Zone Diet and why it works according to Dr. Sears is because of the interplay of foods, the hormones insulin and glucagon, and certain hormone-like compounds known as eicosanoids.

Sears believes that when blood glucose levels increase due to excessive consumption of low-glycemic index carbohydrate-containing foods, that the cells in the pancreas release the hormone insulin. Insulin then signals cells in the body to absorb the excess glucose from the bloodstream and store it as either glycogen in liver and muscle cells or as fat in fat cells (adipose tissues).

However, when blood glucose levels go down, different cells in the pancreas release the hormone known as glucagon. Unlike insulin, glucagon instead gives a counteracting instruction to the liver and muscle cells to release glycogen and convert it back into glucose for use by the body. If glucose levels continue to remain significantly low, the body ultimately turns to burning it fat stores for energy.

According to Dr. Sears, biochemically, carbohydrates stimulate the production of insulin while proteins stimulate the production of glucagon. Thus the interplay between these two hormones and the type of food intake that triggers their secretion by the body plays a significant science behind Dr. Sears' Zone Diet.

The suggestion of Dr. Sears therefore is that dieters need to eat the right ratio of carbohydrates to proteins and fats in order to be able to effectively regulate their blood insulin levels and as a result reduce the body's propensity to store glucose as fat in the body.

By its recommended food intake, the Zone Diet is generally considered a high-protein, low-carbohydrate diet since it promotes the intake of 40% carbohydrate, 30% protein, and 30% fat and is why it is known as the 40-30-30 plan.

Determining the 40:30:30 Ratios

The Zone Diet is a highly structured diet given the fact that dieters are specifically instructed to maintain the 40%-carbohydrates, 30%-protein, and 30%-fats nutrient ratios at every meal and snack they have.

To determine this nutrient ratio, the diet bases the amount of food to be consumed to be relative to the dieter's protein needs. An individual's protein need is calculated based on the person's height, weight, hip and waist measurements and also activity level.

The results from the individual's protein requirements are then used to effectively determine the amount of carbohydrate and fats to be allowed on the diet in order to maintain the "equilibrium" in the body's hormonal secretion. Usually the result of this calculation is a daily diet that ranges from about 1,100 to 1,700 calories.

Foods in the Zone Diet

The Zone Diet categorizes food as either "good" or "bad" and the dieter is therefore required to make sure that each meal comes from the "good" foods to make up the 40-30-30 macro-nutrient ratio.

Essentially, the Zone Diet recommends that 40% of the calories in every meal or snack should come from natural and complex carbohydrates, 30% from lean protein sources, while the balance 30% from healthy unsaturated dietary fats.

Good sources of carbohydrate permitted in the Zone Diet include very small amounts of grains, non-starchy vegetables, oatmeal, barley, and some fruits. They are generally to be natural, complex, and unrefined.

Proteins sources that are considered as "good" by the diet include lean chicken, turkey, and other poultry as well as seafood and egg whites.

Fats that are allowed are small amounts of canola and olive oil, as well as low-fat/non-fat dairy products. Dr. Sears highly recommends the intake of proper amounts of the essential fatty acids - Omega-3 and Omega-6 and in fact the popularity of pharmaceutical-grade omega-3 fish oils is particularly accredited to him.

However, the following types of "bad" foods - according to the Zone Diet - are strictly forbidden: red meat or fatty meats; whole milk dairy products; bread, rice, cereals and most baked foods; egg yolks and potatoes; certain fruits and vegetables such as carrots, bananas, papaya, mangoes, corn, fruit juices in general, and many other fruits.

The aim of the Zone Diet unlike most other diet programs is more to help dieters reduce body fat rather than reaching a particular body weight. The diet therefore aims to help men have only about 15% body fat and women to have a 22% body fat.

The Zone Diet has equally seen its fair share of criticism from nutritionist and dietitians alike. Although most agree with the 30% fat consumption ratio, many however differ on the other two nutrients as some consider the 30% protein ratio as being too high and that the 40% carbohydrate ratio is too low. Other experts view Dr. Sears' theory on insulin as flawed as they argue that there is yet no substantial scientific proof to verify the role insulin plays in weight regulation.

Notwithstanding, most a-list celebrities can swear by the results they have achieved through making use of the Zone Diet and this is perhaps why the Zone Diet is often regarded as a "Celebrity Diet". Then again, some health experts and celebrities alike are of the opinion that the Zone Diet's recommendation do not stray too far from those in the Dietary Guidelines for Americans.

Of equal note is the fact that the popularity of the program has grown in part to the inclusion of Zone Diet meals in the menu of many restaurants. Moreover, the company has developed a program of home-delivered Zone meals for those who don't have the time to prepare their meals themselves or having difficulties preparing them.



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