Metabolism, Vol. 51, No. 7, 2002:

The few studies that have examined body composition after a carbohydrate-restricted diet have reported enhanced fat loss and preservation of lean mass in obese individuals. The role of hormones in mediating this response is unclear. We examined the effects of a 6-week carbohydrate-restricted diet on total and regional body composition and the relationships with fasting hormone concentrations (...)
Compared to body mass at week 0 there was a small but significant decrease in body mass at weeks 3 and 6. There was no change in body mass in the control group. (...)
Fat mass was significantly decreased at week 3 and continued to decrease at week 6. Soft tissue lean body mass significantly increased at week 6. (...)
Adaption to this carbohydrate-restricted diet resulted in a significant decrease in percent body fat and increase in lean body mass. (...)
The small but nonsignificant reduction in voluntary dietary energy intake may have been due to fewer food choices, the higher satiety of fat and protein, or the anorectic effect of ketosis. (...)
We hypothesize that elevated beta-hydroxybutyrate concentrations may have played a minor role in preventing catabolism of lean tissue on the carbohydrate-restricted diet but other anabolic hormones were likely involved (eg. growth hormone)...

Cleveland Clinical Journal of Medicine, Vol. 69, No. 11, 2002:

...results suggest that a very-low-carbohydrate diet favors loss of fat. Water may account for some of the initial rapid weight loss, but it appears that fat loss accelerates and lean tissue is preserved over longer periods. There is no evidence that prolonged very-lowcarbohydrate
diets cause chronic dehydration. (...)
During prolonged fasting or adherence to a very-low-carbohydrate diet, whole-body metabolism gradually shifts toward obtaining a greater percentage of energy from lipid sources, which can result in the production of ketone bodies in the liver. Clinically, ketone body production indicates that lipid metabolism has been accelerated and that all the enzymes involved in metabolic pathways of lipid metabolism (eg, lipolysis, fatty acid transport, beta-oxidation, and ketogenesis) are operational.
During starvation or periods when carbohydrate intake is very low, ketone bodies serve as an alternative oxidative fuel for peripheral tissues to spare carbohydrate and protein. In this sense, ketone bodies could be considered the perfect fuel for dieters.
Catabolism of protein is reduced by ketones, which probably explains the preservation of lean tissue observed during verylow-carbohydrate diets. The small amount of glucose required by the brain and red blood cells can easily be met via gluconeogenesis from protein and fat.
(...)
Collectively, these studies indicate that very-low-carbohydrate diets alter the effects of insulin on oxidative and nonoxidative glucose disposal, favoring storage of glucose as glycogen in muscle. They also appear to prevent insulin-stimulated inhibition of lipid oxidation.
Data from these studies do not support the notion that very-low-carbohydrate diets exacerbate the risk of type 2 diabetes and insulin
resistance; rather, they actually show a potential favorable effect as evidenced by decreased basal endogenous glucose production and
improved insulin-stimulated nonoxidative glucose disposal.
@Eisenbär: Vielleicht solltest Du mal darüber nachdenken:

Volek (who did his doctoral dissertation work at Pennsylvania State University on low-carb eating):
It was thought to be a fad diet and anyone who studied it was questioned as to why you would even study this diet. However, that has really changed. (...)
We're just at the tip of the iceberg in starting to study this diet.