Glucomannan
Also known as: Konjac glucomannan, KGM, Amorphophallus konjac, konjac fiber, konjac root
Effective Dosage
3 g daily (acute); 8 weeks for constipation relief based on study data
What the Science Says
Glucomannan is a highly viscous soluble fiber extracted from the konjac plant root. Clinical trials show it relieves functional constipation, improves bowel movement frequency, and positively shifts gut bacteria composition after about 8 weeks of use. A single 3 g dose can blunt insulin spikes after a meal and increase feelings of fullness, making it a practical tool for blood sugar management and appetite control.
What It Doesn't Do
Not a standalone weight loss solution — results in obesity studies required nearly 6 months and were combined with other fibers. Won't fix constipation overnight. No evidence it burns fat directly. Not a replacement for diabetes medication. No proven benefit for skin conditions or wound healing in humans based on available clinical data.
Evidence-Based Benefits
Glucomannan (KGM) has demonstrated clinically meaningful improvements in functional constipation, including bowel movement frequency, stool consistency, and quality of life scores, alongside favorable shifts in gut microbiota composition in a double-blind RCT in athletes (PMID: 41117955). A single 3 g dose of a chromium-enriched glucomannan-fructooligosaccharide complex significantly reduced postprandial insulin response and improved satiety markers compared to dextrose alone in healthy adults (PMID: 40490608). When combined with other fibers (inulin, psyllium), glucomannan supplementation over 180 days was associated with significant reductions in body weight and composition in individuals with obesity carrying specific genetic polymorphisms (PMID: 38398881).
Moderate EvidenceEffective at: 3 g per single dose (acute); 8 weeks of supplementation studied for constipation; No single universal established dose across all outcomes
Source: auto-research
Absorption & Bioavailability
Poor (as intended) — glucomannan is not absorbed but acts in the gut by forming a viscous gel that slows digestion and feeds beneficial bacteria. Its effects are local to the gastrointestinal tract.
Red Flags to Watch For
- Must be taken with plenty of water — glucomannan can swell and cause choking or esophageal blockage if swallowed with insufficient liquid
- May slow absorption of oral medications — take medications at least 1 hour before or 4 hours after glucomannan
- Many products combine glucomannan with other fibers or ingredients (inulin, psyllium, chromium), making it hard to isolate glucomannan's specific effects
- Most clinical trials are short-term (8–26 weeks); long-term safety data is limited in the provided studies
- Products marketed for weight loss often overstate results — the weight loss seen in studies was modest and occurred over 6 months
Research Sources
- PubMed
- NIH DSLD
This information is for educational purposes only and is not medical advice. Always consult a healthcare professional before starting any supplement regimen. Last updated: 2026-04-06