Glucomannan is a water-soluble dietary fibre.

Like other soluble fibres, it’s believed to promote weight loss in several ways

• It’s very low in calories. 

• It takes up space in your stomach and promotes a feeling of fullness (satiety), reducing food intake at a subsequent meal.

• It delays stomach emptying, contributing to increased satiety.

• Like other soluble fibres, it reduces the absorption of protein and fat.

It also feeds the friendly bacteria in your intestine, which turn it into short-chain fatty acids like butyrate, shown to protect against fat gain in some animal studies. 

Feeding your gut bacteria may also have other benefits. Some studies have shown a correlation between altered gut bacteria and body weight. 

Glucomannan differs from most other soluble fibres, as it's exceptionally viscous, making it particularly effective for weight loss.

SUMMARY

Like other soluble fibres, glucomannan absorbs water in your stomach and contributes to feelings of fullness. In addition, it may promote reduced calorie intake and weight loss in other ways.