A dietary fiber from the tuberous root of the Amorphophallus konjac plant,1 glucomannan has multiple dietary functions. Due to its ability to soak up and hold water, the fiber begins to form a gelatinous mass that expands and fills the stomach.

As it progresses through the stomach and small intestine, this mass induces a feeling of satiety.2 This finding led to industrial interest in using glucomannan as a weight-loss supplement.


Glucomannan is found in several commercial products promoting weight loss. Data from good-quality clinical trials is not available, however, to either support or refute that function. 

The A. konjac plant is a perennial exotic found naturally in most areas of Asia. Called by common names such as Devil’s tongue, it produces a flower with a single, elongated center wrapped in a large leaf. The center spike of the flower and its potato-shaped tuber are two of the parts that are used in nutritional supplements. 

Due to its unique chemistry, salivary and upper gastric enzymes do not dissolve and break down glucomannan. It is as the fiber passes into the colon that it begins to exert its potent ability to absorb water. By weight, each gram of glucomannan fiber absorbs 50 times its weight in water or more as it passes through the colon and begins a rapid fermentation process.1

This article originally appeared on Clinical Advisor