In addition to blocking carb digestion, carb blockers may affect some of the hormone involved in hunger and fullness. They may also help slow stomach emptying after a meal.
One reason for this effect may be because bean extracts also contain phytohaemagglutinin. This compound can increase the levels of some hormones involved in fullness.
One rat study found that the phytohaemagglutinin in carb blockers did cause a significant decrease in food intake. The rats that had been given the compound ate between 25–90% less. However, this effect lasted only a few days.
However, there may be other ways that carb blockers decrease appetite.
Similar studies found that a carb blocker supplement could decrease the amount of food the rats ate by 15–25% over a consistent period of time and even caused them to eat less of foods that are high in fat and sugar . This effect has not been well-researched in humans, but one recent study found that a concentrated, standardized bean extract did decrease feelings of hunger, probably by suppressing levels of the hunger hormone ghrelin.