Actually, Doiron...I'm not trying to argue that it's the lack of carbs that prevent loss of lean body mass, it's the presence of adequate dietary protein that most low fat/low calorie diets are lacking. If fat is low and carbs are high and you still want to keep your calorie levels down, protein gets sacrificed on the calorie alter.
There was another study that I ran across where the carb intakes for both groups were not what could be considered "low" carb for either group, although one group was lower than the other. The difference was that one group only got 68 grams of protein per day while the other got 125 grams. The group with the higher protein intake lost the least amount of lean body mass. The study Follows:


Reference:
Layman, D.K., Boileau, R.A., Erickson, D.J., et al., "A Reduced Ratio of Dietary Carbohydrate to Protein Improves Body Composition and Blood Lipid Profiles During Weight Loss in Adult Women," The Journal of Nutrition, 133(2), 2003, pages 411-417.

Summary:

Claims about the merits or risks of carbohydrate (CHO) vs. protein for weight loss diets are extensive, yet the ideal ratio of dietary carbohydrate to protein for adult health and weight management remains unknown. This study examined the efficacy of two weight loss diets with modified CHO/protein ratios to change body composition and blood lipids in adult women. Women (n = 24; 45 to 56 y old) with body mass indices >26 kg/m(2) were assigned to either a CHO Group consuming a diet with a CHO/protein ratio of 3.5 (68 g protein/d) or a Protein Group with a ratio of 1.4 (125 g protein/d). Diets were isoenergetic, providing 7100 kJ/d, and similar amounts of fat ( approximately 50 g/d). After consuming the diets for 10 wk, the CHO Group lost 6.96 +/- 1.36 kg body weight and the Protein Group lost 7.53 +/- 1.44 kg. Weight loss in the Protein Group was partitioned to a significantly higher loss of fat/lean (6.3 +/- 1.2 g/g) compared with the CHO Group (3.8 +/- 0.9). Both groups had significant reductions in serum cholesterol ( approximately 10%), whereas the Protein Group also had significant reductions in triacylglycerols (TAG) (21%) and the ratio of TAG/HDL cholesterol (23%). Women in the CHO Group had higher insulin responses to meals and postprandial hypoglycemia, whereas women in the Protein Group reported greater satiety. This study demonstrates that increasing the proportion of protein to carbohydrate in the diet of adult women has positive effects on body composition, blood lipids, glucose homeostasis and satiety during weight loss.


The diet consisted of roughly 1700 calories for each group. One group got 125 grams of protein, 50 grams of fat and 187 grams of carb. The other group got 68 grams of protein, 50 grams of fat and 244.5 grams of carb. The group with the higher protein level lost only slightly more weight than the lower protein group, but more of the loss was fat and less was lean body mass than the lower protein group.