This section gives an abbreviated picture of the science behind the Zone. Just as you do not need to know how your car works to drive it, to get into the Zone you do not need to understand how the Zone works. However if you want to know the hows and whys read on.

In the beginning

Dr Barry Sears came from a family where the men all died in their early fifties from heart attacks. He realised that he wouldn’t make it much past 50 if he didn’t do something so he started to research the effects of food on the body. By the 1990s he had created a method of eating that balanced the body to give optimal health. As a side effect overweight people rapidly shed fat to attain their ideal weight. Dr Sears’ work was based on the fact that the hormones that are the drivers of the body’s key functions are directly related to what we eat and how we eat it. Today many other programmes use the knowledge that Dr Sears unlocked including the best choice of carbohydrates in the low GI and GL diets and the best choices of fats as in the Mediterranean diet.

Insulin – the key to the Zone

In the Zone the secret to weight loss and good health is controlling insulin levels. Insulin is released from the pancreas in response to a rise in blood sugar levels. Insulin is a storage hormone and when present in large amounts it causes sugar from excess carbohydrates to be converted into fat – instead of being available for energy. High insulin levels also prevent us accessing stored body fat for energy. This action is a legacy of our hunter gatherer ancestors. It enabled them to store food as fat and protect body fat stores in times of plenty so that they would be prepared for times of need during famines. But with today’s refined carbohydrate products and plentiful food availability the constant over production of insulin can cause weight and health problems.

In the Zone we quite simply select and balance food to control our blood sugar levels. Eating to control blood sugar levels enables you to control responding insulin levels in a tight ‘zone’ in the bloodstream. Eat to control your blood sugar levels and you can control your insulin levels. Control your insulin levels and you will control your weight, your health and your performance. Because lowered levels of insulin enable us to access body fat for energy this allows us to switch from fat storing to fat burning. Excess insulin also disturbs the balance of many of the hormones that are vital to our health. This is why many overweight people often have a number of other health problems. Click here for more information about food.


The January 2005 edition of the highly respected international scientific journal Diabetologia concluded that in the context of a year-long comparative diet study from Otago University that “the HP (sic) Zone Diet appears to be the most appropriate overall approach to reducing the risk of cardiovascular disease and type 2 diabetes” It is also the best dietary strategy for those who already suffer from these conditions. Read more on this study.

Type 2 (adult onset) diabetes is due to the impaired ability of insulin to get glucose (blood sugar) out of the bloodstream and into the body’s cells for fuel. As this problem becomes worse blood sugar levels get increasingly higher. High blood sugar levels are very damaging to the body affecting the kidneys, nerves, eyesight and blood supply to tissues etc. Diabetics are much more likely to suffer from heart attacks and strokes. They are at risk of kidney failure, blindness, impotence and losing toes, feet and limbs.

Zone Nutrition has proved very effective in improving diabetes and reducing the necessity for medication. The reason for this is twofold and simple:

  1. We show people how to eat appropriate foods to put less sugar into their bloodstream. This means less demand on their body and less medication required to lower their blood sugar levels.
  2. Improved ability of insulin to provide the body’s cells with access to blood sugar. Impaired ability to take sugar from the bloodstream is caused by inflammation – Zone Nutrition is anti- inflammatory.

Eicosanoid Hormones

Dr Barry Sears realised that the key to reducing risk factors for heart disease and other degenerative diseases lay in balancing eicosanoid hormones in the body. Every time we eat we trigger off incredibly complex hormonal reactions that regulate our body. Eicosanoid hormones perform hundreds of tasks in the body all the time. They exist in pairs, each affecting opposite tasks of the same function such as stimulation and depression of the immune system, inflammatory and anti-inflammatory activity and release and shut off of serotonin, balancing of histamine and antihistamine etc. When these hormones are in harmony we are in good health but when out of balance they can cause ill health. Imagine one hormone turning on a tap and its opposite number turning the tap off. The ideal flow is a medium stream but if the hormones get out of balance the tap can be turned on too much or shut down.

Some effects of disturbed eicosanoid hormone balances are arthritis, asthma, allergies, depression, high blood pressure and cholesterol and other factors related to heart disease, depressed immune system, poor sleep patterns, sleep apnoea, heart burn, dry wrinkled skin and brittle nails and hair.

Insulin again plays a key part in the balance of these hormones – if insulin levels are too high the balance of eicosanoid hormones is disturbed. Eicosanoid hormones are made from Omega-6 essential fatty acids. Too much of the wrong fats and not enough Omega-3 fats (found in fish oil) can also disturb the balance of these hormones.

The basic Omega-6 fatty acid is linoleic acid (LA), which is found in most things we eat. It is converted by a number of steps to dihomo gamma linolenic acid (DGLA). This is the building block of eicosanoid hormones, both good and bad. ‘Bad’ is somewhat of a misnomer as all eicosanoid hormones trigger functions essential to life but in excess some can cause health problems. The critical factors that determine whether we convert DGLA into too few good hormones and too many bad hormones are insulin and Omega-3 fatty acids. Excess insulin will trigger over production of the enzyme delta 5 desaturase, this converts DGLA into arachidonic acid (the building block of “bad” hormones). Omega-3 fatty acids found in fish oil suppress Delta 5 desaturase allowing more DGLA to be diverted into making good hormones and less into conversion to arachidonic acid and bad hormones.

Thus the basis of Zone Nutrition is eating to control insulin levels and supplementing with Omega-3, the missing fat in our diet.

Relevant scientific studies

And if you are keen to learn more we recommend:
— Dr Barry Sears’ books, such as ‘Enter the Zone’. For a more technical perspective try his
‘Anti-aging Zone’ book.