The zone diet, developed by Dr Barry Sears PhD, promises to reduce weight, alleviate disorders and improve health and sports performance. But can one diet do all this?
Dr Sears presents his argument using the Hunter-Gatherer ethos of eating a diet consisting of proteins and predominantly fruits and vegetables. His argument is that many centuries ago, carbohydrates in their refined dense forms, such as rice, pasta and bread, did not exist and that a diet high in these causes a hormonal imbalance. He also claims that certain types of hormones, when elevated, have an adverse affect on health and physiology. Dr Sears accuses insulin of having this highly immoral stance.
Insulin, as you know, is a hormone released by the pancreas and is responsible for maintaining blood sugar at its required levels between approximately 3.5mmol and 10mmols per litre of blood by transferring blood glucose to the cells as glycogen. Its opposing hormone, glucagon, is responsible for the reverse action if blood sugar levels should drop.
The zone diet assumes eicosanoids (various types of hormones) are bad for health and that eating refined carbohydrates promotes insulin release, in turn promoting these eicosanoids.
High protein or carb?
The zone diet recommends a daily intake of protein between 1.8g and 2.0g/kg/d which equates to a 40/30/30 percentage ratio of carbs/protein/fat. The evidence is controversial as to the benefits and the effects of high protein/high carbohydrate diets and their effects on the hormone physiology. Cheuvront (1999) reports no favourable shift of hormone response in relation to the 40/30/30 diet and many authors support high carbohydrate diets to be effective for weight management and sports performance.
The bottom line is that any diet that is restrictive will have a reducing effect on total calorie consumption over time. This restriction will ultimately therefore result in weight loss, whether it is high carb or high protein. The zone clearly reduces total calorie intake as it is much harder to eat the amount of dense calories from protein sources than it is from sources such as pasta, rice, bread and potatoes.
The zone, as with many other diets, is prescriptive in its eating pattern. However, it has two extremes of recommended eating patterns, one of which is ultimately a message of healthy eating. The balanced approach is to divide your plate into three equal sections, one with a lean protein of about the size of the palm of your hand and the remaining two parts filled with whole grains, vegetables and fruit with a small sprinkling of monounsaturated fats (my recommendation would be polyunsaturated fats such as fish oils and seed oils). To a point the above recommendations are not too far away from a healthy eating pattern although if you need more calories for training that would become a primary importance.
The extreme of the zone is to work in equal blocks of eating; ie, four blocks of protein, four of fat and four of carbohydrate. This could lead to obsessive psychological control mechanisms that may result in deprivation and failure.
It is important that when looking to follow any fat loss diet that you are able to evaluate the message from the plan and make sure that it is the right eating pattern for you.
A good weight loss plan should:
- Reduce calories, remaining balanced across all food groups (the first zone message, if taken from a health perspective).
- Report a slow and steady weight loss.
- Fit with your own eating pattern and choice of foods (The zone’s choices of foods are extremely limited on the supermarket shelf).
- Satisfy you and not cause fatigue.
- Give out a health message – not just about weight loss.
- Not promote disordered eating habits (eg, the zone blocking)
- Not reduce calories below 1,200 per day.
- Be devised by a suitably qualified person.