Low carbohydrate diets show beneficial effects on weight loss, fat loss, inflammation and cardiovascular risk, when compared to traditional low fat diets. The low carbohydrate diets have been discussed for many decades, but were more recently, popularised by Atkins and Sears with books describing the Atkins and Zone diets, respectively. Both of these diet are based on limiting carbohydrate content of the diet, but they achieve this in different ways. The Atkins diet is a ketogenic diet formulated by Robert Atkins whereby the individual must eliminate all carbohydrates from the diet to enter a state of ketosis (although a later maintenance stage does allow some carbohydrates). In contrast the Zone diet, formulated by Barry Sears, is an isocaloric diet whereby carbohydrates are limited to no more than around 30 to 40 % of energy intake, while at the same time emphasising low glycaemic index carbohydrates. Both diets aims to limit postprandial glycaemia, and both have shown to be beneficial to fat loss and disease risk.
However, the Zone diet is arguably easier to follow because it allows the consumption of some carbohydrates. Although effective, the Atkins diet may be more difficult to adhere to due to a more limited and less palatable variety of foods being available to the individual. The question therefore is is the extra effort required to maintain adherence to the Atkins diet rewarded by greater fat loss and better health? Studies have compared ketogenic Atkins style diets with isocaloric Zone diets. For example, in one study1, researchers fed obese individuals either a ~ 5 % carbohydrate diet to induce ketosis or ~ 40 % carbohydrate diet, each diet being based on recommendations by Atkins and Sears, respectively. After 6 weeks weight loss in the ketogenic diet group was 6.3 kg whereas the weight loss in the isocaloric diet group was 7.2 kg. However, fat loss in the ketogenic group was 3.4 kg, and the fat loss in the isocaloric group was 5.5 kg.
These results suggest that the isocaloric diet that limits carbohydrates to 40 % of intake produces superior weight loss and superior fat loss to a ketogenic diet. The percentage of the weight that was lost was fat was 54 % for the ketogenic diet and 76 % for the Zone diet. The zone diet therefore causes less loss of lean tissue compared to the ketogenic diet. However, it is difficult to recommend one diet over the other based on this study as both diets were effective and safe. Individual preference for the style of the diet should therefore dictate which diet is chosen as a fat loss strategy. Interestingly the arachidonic acid to eicosapentaenoic acid ratio, a measure of the possible inflammatory milieu of the body was more adversely affected by the ketogenic diet, when compared to the Zone diet. This may reflect the higher intakes of animal fats in the ketogenic diet, something which increases the cell membrane concentrations of arachidonic acid significantly. However, substituting fish for red meat would easily correct this detrimental effect.
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