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Diets in Focus: The Zone Diet: by Emily Greenfield

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Intro
We all know that overweight and obesity are increasing in prevalence in Australia and throughout the world. The latest National Health Survey (2007-08) showed 7 out of 10 men and 6 out of 10 women in Australia were overweight or obese. Weight loss can be a difficult and slow process and solutions that offer rapid and easy weight loss, such as fad diets, are enticing despite often being nutritionally unbalanced and based upon questionable science and evidence.

The Zone Diet Hypothesis:

The Zone, written by Dr Barry Sears, declares food regulates hormones such as insulin and eicosanoids with drug like precision resulting in weight loss and good health. The Zone advocates a high protein, moderate fat and restricted carbohydrate (CHO) intake and includes lean meats and low glycaemic index (GI) carbohydrate, whilst avoiding saturated fats, grains, starchy vegetables and some fruit.

The Evidence: Research in peer reviewed scientific journals provides no evidence of a connection between diet, hormones, eicosanoids and health. The ‘ten red flags of junk science’: This list was developed by the American Dietetic Association to identify food and nutrition misinformation in the public domain. These red flags are commonly associated with popular fad diets. At least seven of the red flags can be detected in The Zone including recommendations that promise a quick fix, claims that sound too good to be true and dramatic statements. These strategies are used to great effect to market The Zone and are even present on the cover to entice vulnerable consumers. To convince readers the diet has credible scientific foundations, complex eicosanoid Nobel Prize winning research is used as a basis for the diet and great emphasis is placed on Barry Sears’ PhD and background in science despite being unrelated to nutrition. Finally, supporting data for the diet includes personal anecdotes and unpublished pilot studies - often without a control group - concerning amazing weight loss and chronic disease prevention/cure.

The Zone theory is generally not supported by scientific evidence and it is apparent that any weight loss achieved on the diet, like most fad diets, is purely through the restriction of kilojoules and the loss of fluid. However, certain recommendations made by Dr Sears such as a low GI diet and long chain omega 3 intake may reduce the risk of chronic disease. Nutritional evaluation: A one-week meal plan based on the dietary guidelines of The Zone was analysed for a female, aged 30 years with a body mass index (BMI) of 30 (89 kg/1.72 m2) who undertakes light exercise. I will just point out here that producing a diet from the book that met The Zone dietary guidelines was a pretty complicated process and I am a nutritionist! It turns out The Zone is a low kJ diet (6032 kJ a day), which provides less than 60% of the energy required per day for a female of this size. The diet provides inadequate amounts of thiamin, folate, vitamin A, calcium, iron and is particularly low in iodine. Iodine and folate are important nutrients for women of child bearing age due to their role in the normal development of a fetus. Sodium intake is considerably higher than the recommended upper limit of intake while fibre and all other micronutrients are provided in adequate amounts.

Diets in Focus: The Zone Diet: by Emily Greenfield
Emily Greenfield
Dietitian