Glucomannan

Glucomannan is a sugar made from the root of the konjac plant that has been used for centuries in traditional Japanese cooking as a thickener or gelling agent.
It's so renowned in Japan that it even has its own nickname-"the broom of the intestines"-which gives you a pretty good idea of how it works.
For just a few calories, glucomannan creates a sense of fullness by absorbing water and expanding to form a bulky fiber in your stomach.
It absorbs so much liquid that a small amount of glucomannan added to a glass of water turns the entire content into a gel.
These unique properties are believed to mediate its effects on weight loss.