High protein low carbohydrate diets have weight loss benefits. In particular, high protein low carbohydrate diets tend to increase satiety, increase lean mass, increase fat loss and improve body composition, when compared to low protein high carbohydrate diets. High protein diets are relatively easy to follow for those who can consume meat and other animal products as these foods tend to be high in protein. Lacto-ovarian vegetarians too can benefit from certain products of animal origin such as eggs and milk, and can fortify their diet with whey protein. However stricter vegetarian such as vegans may find it more difficult to increase the protein content of their diet as excluding these animal products limits the bioavailability and range of proteins available. However, one solution may be the consumption of soy protein, which of the vegetable proteins has one of the highest biological activities, making it close to, but not as complete as animal protein for human needs.
Comparisons of high protein low carbohydrate diets based on animal or soy proteins have been performed. For example, in one study1, researchers investigated the physiological responses to soy or meat during a weight loss diet in obese men. Subjects consumed a maintenance diet and then adopted either a high protein soy based or high protein meat based diet (chicken and beef) for 2 weeks, in a crossover design. The macronutrient composition of the high protein diets was 30 % protein, 30 % fat, 40 % carbohydrate. Over the two weeks of the high protein diets the soy group lost 2.41 and the meat group lost 2.27 kg of body weight. This difference in weight loss was not different between the two protein sources. Analysis of other parameters showed that changes to hunger ratings, lean mass and percentage fat mass did not differ between the two groups. Soy as a protein source may therefore be a suitable substitute for meat in those who are unable or prefer not to consume the latter. Powdered soy protein is also available.
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