That weight loss requires calorie restriction is a fallacy. However, despite evidence clearly showing that non-calorie restrictive diets are effective, many people continue to believe that they must forcibly restrict energy intake in order to cause weight loss. The main problems with energy restrictive diets are numerous, but primarily revolve around the loss of muscle that they cause as well as the difficulty in maintaining them over the long term. Evidence suggests that attrition rates on studies involving energy restrictive diets may be 15 to 50 % within a year. This supports the data showing that after an initial weight loss period, many people then regain the lost weight and in many cases gain further body fat, such that their body composition deteriorated following an energy restricted diet. The trick with weight loss, or more correctly fat loss, is to improve the quality of the diet and reduce intakes of lower quality foods, particularly those which are known to cause insulin resistance, such as refined carbohydrates and sugar.
As refined carbohydrates such as sucrose, fructose and high fructose corn syrup are the main dietary drivers of insulin resistance, it makes logical sense that lowering these dietary components will improve insulin sensitivity and thereby cause fat loss. It might be expected then that high quality traditional diets , devoid of refined carbohydrates, and low carbohydrate diets, that by definition exclude refined sugars, are able to cause significant weight loss. In fact this is what we see in many studies. Diets low in sugar, even if no energy restriction is imposed, tend to cause greater fat loss when compared to energy restrictive diets. This explains the popularity of low carbohydrates such as the Atkins diet. For example, in one study1, researchers compared a typical Mediterranean diet, a low carbohydrate Atkins style diet and a low fat diet. The Mediterranean diet and the low fat diet were both energy restricted, but the low carbohydrate diet was ad libitum, which meant no energy restriction was imposed on the subjects.
The results of the study showed that the mean weight loss was 2.9 kg in the low fat group, 4.4 kg in the Mediterranean group and 4.7 kg in the low-carbohydrate group. Therefore the regimen that requested no calorie restriction and gave free choice of food within the context of being low in carbohydrate, caused the most weight loss all all the diets. This highlights the absurdity of claiming that energy restrictive diets are necessary for weight loss. The likely reason that the low carbohydrate diet was so effective was because eliminating carbohydrate is an effective method to improve insulin sensitivity. Low carbohydrate diets, by their very nature, eliminate or greatly reduce intakes of all refined carbohydrates including fructose and fructose containing sugars, which are primary drivers of the insulin resistant state. The low carbohydrate diet group also experienced the largest reductions in blood cholesterol levels, despite following a high animal fat type diet, which highlights the absurdity of the lipid theory of cardiovascular disease.
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