Glucomannan
Glucomannan is a type of fiber found in the roots of the elephant yam, also called konjac.
How it works: Glucomannan absorbs water and becomes gel-like. It “sits” in your gut and promotes a feeling of fullness, helping you eat fewer calories.
Effectiveness: Three human studies showed that glucomannan, combined with a healthy diet, can help people lose 8-10 pounds (3.6-4.5 kg) of weight in 5 weeks.