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Glucomannan

A natural appetite suppressant and fiber supplement used for weight loss and Digestive regularity.

Evidence · Grade B
Human trial evidenceTraditional useInteraction risk

Glucomannan is a highly viscous dietary fiber from konjac root studied for its potential role in weight management. It may influence satiety and metabolic markers through gut microbiome modulation and delayed gastric emptying.

Last reviewed June 13, 2026 · AI-assisted, human-reviewed
Glucomannan is a water-soluble dietary fiber derived from the root of the konjac plant (Amorphophallus konjac). As a fermentable polysaccharide, it has been investigated for its capacity to form a viscous, gel-like mass in the digestive tract. This property is frequently studied in the context of weight management and metabolic health, as the fiber's expansion may influence satiety and the absorption rate of macronutrients. Emerging research explores how prebiotics like glucomannan interact with gut microbiota to influence glucose metabolism and energy expenditure, particularly in populations with metabolic risk factors. While its physical properties are well-documented, clinical outcomes are often dependent on adherence and sufficient hydration.

Quick answer

What it is: Glucomannan is a water-soluble dietary fiber derived from the root of the konjac plant (Amorphophallus konjac).

May support:Obesity

Evidence:Evidence · Grade B

Evidence Summary

Evidence · Grade B

Evidence for glucomannan in obesity management is rooted in its physical properties as a soluble fiber. Research into prebiotics highlights their role in inducing beneficial changes in gut microbiota composition, which may improve glucose metabolism and energy regulation in metabolically compromised individuals.

Last reviewed · Jun 2026

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Why It Works

Glucomannan acts as a bulking agent that absorbs significant amounts of water, promoting a feeling of fullness. In the gut, it serves as a prebiotic, undergoing fermentation by microbiota to produce short-chain fatty acids which may influence metabolic signaling.

How it works in more detail

Upon ingestion, glucomannan absorbs water to form a dense fiber matrix. This physical mass delays gastric emptying and slows the transit time in the small intestine. This deceleration may blunt the postprandial glucose response and interfere with the enterohepatic circulation of bile acids. At the microbial level, prebiotic fibers are fermented by the gut flora, potentially enhancing the abundance of beneficial bacteria. This process can influence the production of signaling molecules involved in energy expenditure and intestinal permeability, which are critical factors in the management of obesity and prediabetic states.

How to use

Always consult a qualified clinician.

Editorial guidance

Suggested dosage
1-4 grams per day, divided into 2-3 doses, taken with a large glass of water before meals.
Research dosage range
Commonly studied in doses of 1 gram taken three times daily, approximately 30 to 60 minutes before meals.
Typical onset
Acute effects on satiety may occur within 30 to 60 minutes of ingestion; metabolic and weight-related changes typically require consistent use over 4 to 12 weeks.
Typical forms
capsule, powder, food additive
Quality markers
Look for products that specify the percentage of glucomannan, as purity can vary. Ensure the product is free from unnecessary fillers and additives. Third-party testing for purity and contaminants can also be a good indicator of quality.
Medication interactions
  • oral medications (may reduce absorption)
Avoid if
  • difficulty swallowing
  • esophageal obstruction
  • gastrointestinal blockage

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Suggested dosage

1-4 grams per day, divided into 2-3 doses, taken with a large glass of water before meals.

General guidance — discuss specifics with a clinician.

Active medicinal compounds

Glucomannan (a polysaccharide)

Traditional use

The konjac plant, from which glucomannan is derived, has been traditionally used in Asian cuisine for centuries, particularly in Japan and China, as a food ingredient (e.g., konjac noodles, konjac jelly). Its use in traditional medicine systems is less documented as a distinct remedy, but its fiber-rich properties would have contributed to digestive health.

Safety

Safety warnings

Glucomannan must be taken with adequate liquid (at least 8 ounces of water) to prevent it from swelling and obstructing the throat or esophagus. Individuals with structural abnormalities of the esophagus or swallowing difficulties should avoid use. It may also interfere with the absorption of oral medications if taken simultaneously.

Avoid if

  • difficulty swallowing
  • esophageal obstruction
  • gastrointestinal blockage

Medication interactions

  • oral medications (may reduce absorption)

Reported side effects

  • bloating
  • flatulence
  • abdominal discomfort
  • diarrhea
  • constipation (if not enough water is consumed)

General guidance — discuss specifics with a clinician.

Evidence ecosystem

Scientific literature, clinical guidance, government sources, ongoing research, traditional use, and lived experience — grouped by source type and quality.

Overall grade (B)

Evidence for glucomannan in obesity management is rooted in its physical properties as a soluble fiber. Research into prebiotics highlights their role in inducing beneficial changes in gut microbiota composition, which may improve glucose metabolism and energy regulation in metabolically compromised individuals.

Filter by source type

Randomized Human Trials(1)

Controlled human studies with random assignment.

High Quality

  • Impact of Combined Prebiotic Galacto-Oligosaccharides and Bifidobacterium breve-Derived Postbiotic on Gut Microbiota and HbA1c in Prediabetic Adults: A Double-Blind, Randomized, Placebo-Controlled Study.

    Beteri B, Barone M, Turroni S, Brigidi P, Tzortzis G, Vulevic J · Nutrients · 2024

    The complex interactions between intestinal microbiota and metabolic disorders are well-documented, with implications for glucose metabolism, energy expenditure, and intestinal permeability. Prebiotics induce beneficial changes in gut microbiota composition in prediabetes, while postbiotics can enhance gut barrier function, complementing each other to improve glucose metabolism and insulin sensitivity. This study investigated the effects of a 12-week dietary fibre (DF) supplement on gut health, metabolic function, and diet. The supplement contained konjac glucomannan (KGM), galacto-oligosaccharides (GOSs), and exopolysaccharides (EPSs) from Bifidobacterium breve. In a randomised, double-blind, placebo-controlled, parallel-group clinical trial, 53 prediabetic volunteers were randomly assigned to either a daily DF supplement (YMETA) or a placebo (cellulose microcrystalline) for 12 weeks, followed by a 4-week follow-up. Measurements included gut microbiota composition, glycated haemoglobi

    Randomized TrialPubMedHigh Quality

Animal Studies(1)

Preclinical animal research — not a substitute for human evidence.

Low Quality

  • MicroRNA-31 Reduces Inflammatory Signaling and Promotes Regeneration in Colon Epithelium, and Delivery of Mimics in Microspheres Reduces Colitis in Mice.

    Tian Y, Xu J, Li Y, Zhao R, Du S, Lv C · Gastroenterology · 2019 · n=82

    Levels of microRNA 31 (MIR31) are increased in intestinal tissues from patients with inflammatory bowel diseases and colitis-associated neoplasias. We investigated the effects of this microRNA on intestinal inflammation by studying mice with colitis. We obtained colon biopsy samples from 82 patients with ulcerative colitis (UC), 79 patients with Crohn's disease (CD), and 34 healthy individuals (controls) at Shanghai Tenth People's Hospital. MIR31- knockout mice and mice with conditional disruption of Mir31 specifically in the intestinal epithelium (MIR31 conditional knockouts) were given dextran sulfate sodium (DSS) or 2,4,6-trinitrobenzene sulfonic acid (TNBS) to induce colitis. We performed chromatin immunoprecipitation and luciferase assays to study proteins that regulate expression of MIR31, including STAT3 and p65, in LOVO colorectal cancer cells and organoids derived from mouse colon cells. Partially hydrolyzed alpha-lactalbumin was used to generate peptosome nanoparticles, and

    Animal StudyPubMedLow Quality

Limitations: Many studies on glucomannan and gut health involve small sample sizes or animal models, which may not translate directly to human weight loss outcomes. Preclinical data regarding intestinal inflammatory pathways and microRNA signaling often utilize controlled environments that do not account for the complexity of human dietary habits.

This page is educational. Statements use phrases like "may support" and "has been studied for"because no remedy here is approved to cure, treat, or reverse any condition. Discussion happens on the ailment pages — community statistics here are derived from those reports. Always consult a qualified clinician.

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