Carb blockers may not cause weight loss on a normal diet because fermented carbohydrates still provide calories.

“Now, they don't seem to cause weight loss when you just do it in a normal diet. Now, why is that? Well, all it does is once those carbohydrates get to the large intestine and your bacteria get a hold of them, they start fermenting them to volatile fatty acids, which get reabsorbed into your liver. So you don't get the increase in blood glucose. But you still get almost all the calories from it. It's just in a different form.”