Glucomannan
Glucomannan is a natural soluble fibre from konjac root that expands in the stomach to help you feel full, sometimes used as a weight-loss supplement.
Plain English
Patient-Friendly Explanation
Glucomannan is a type of natural fibre that comes from the konjac plant. It can absorb a lot of water and swell in the stomach, which helps you feel full and eat less. It is sold as a supplement, but it only helps as part of a healthy diet and must be taken with plenty of water.
Medical
Clinical Definition
Glucomannan is a highly viscous, water-soluble polysaccharide of D-glucose and D-mannose derived from Amorphophallus konjac. Its viscosity delays gastric emptying and increases gastric distension, enhancing satiety; meta-analyses of randomised trials report small but statistically significant weight reductions of roughly 1 kg on average over 8–12 weeks versus placebo. It can reduce the absorption of other oral medicines taken at the same time, so it should be taken at least two hours apart from other medications, and adequate fluid intake is essential to avoid oesophageal obstruction.
Key Insight
Why It Matters
Supplements such as glucomannan are not a substitute for medical weight management, but they can complement a balanced plan when used safely. Dr Joseph Wang can advise which supplements are worth taking — and which are a waste of money.
Sources
Reviewed against standard medical references.
Medically reviewed by
Family Physician & Registered Acupuncturist, Accord Medical Clinic. MBBS (NUS), Graduate Diploma in Family Medicine (NUS), Graduate Diploma in Acupuncture (Singapore College of TCM).
Last reviewed: August 2026
This page is general health education, not medical advice. Whether any treatment is appropriate for you is a decision made in consultation after assessment.