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Glucomannan
Glucomannan is the soluble fiber from konjac root.
- Evidence
- Mixed Evidence
- Category
- Weight Management
- Best form
- Powder mixed into a full glass of water (safest format - hydrates before swallowing)
- Effective dose
- 3g/day split into three 1g doses taken with at least 8oz of water 15-30 minutes before each main meal. This is the dose specified in the EFSA-authorized health claim. Some lipid-lowering trials used 4g/day. Higher doses do not appear to increase efficacy and worsen GI tolerability.
- Lab tested
- 3 of 9 products
- Category
- Weight Management
- Best form
- Powder mixed into a full glass of water (safest format - hydrates before swallowing)
- Effective dose
- 3g/day split into three 1g doses taken with at least 8oz of water 15-30 minutes before each main meal. This is the dose specified in the EFSA-authorized health claim. Some lipid-lowering trials used 4g/day. Higher doses do not appear to increase efficacy and worsen GI tolerability.
- Lab tested
- 3 of 9 products
Key takeaways
- →EFSA approved a weight-loss health claim at 3g/day in three divided doses with water before meals, but the largest meta-analysis (Onakpoya 2014) found no significant overall effect - treat it as a modest satiety aid, not a weight-loss intervention.
- →Lipid evidence is stronger than weight evidence: Ho 2017 meta-analysis shows ~10% LDL reduction at 3g/day - this is the more replicable effect.
- →Safety rule: always take with at least 8oz of water. Avoid solid tablets - they can expand in the esophagus before reaching the stomach. Use powder or capsules with adequate water.
- →Lipozene (the heavily-advertised TV brand) was the subject of a 2005 FTC action requiring $1.5 million in consumer redress over deceptive weight-loss claims. The active ingredient is the same glucomannan you can buy for a fraction of the price.
- →If you want a soluble fiber with stronger evidence and an FDA-approved heart claim, psyllium husk is the better-studied alternative.
What Is Glucomannan?
Glucomannan is the soluble fiber from konjac root. It is one of the few weight-loss supplements with a regulator-authorized health claim - EFSA's NDA Panel approved an Article 13 claim in 2010 for body weight reduction at 3g/day in three divided doses with water before meals, in the context of an energy-restricted diet. That is the highest bar a supplement weight claim clears in the EU. The U.S. has no equivalent approved claim.
The trial picture is more mixed than the EFSA claim implies. Sood, Baker & Coleman's 2008 meta-analysis (14 trials, n=531) found glucomannan reduced body weight by 0.79 kg, LDL cholesterol by 16 mg/dL, total cholesterol by 19 mg/dL, triglycerides by 11 mg/dL, and fasting glucose by 7 mg/dL versus placebo. That is the result most often cited in marketing copy.
Onakpoya, Posadzki & Ernst's 2014 meta-analysis (Journal of the American College of Nutrition, 9 trials, 8 in meta-analysis) found something different: across all RCTs, glucomannan did not produce statistically significant weight loss (MD -0.22 kg, 95% CI -0.62 to 0.19). A sensitivity analysis excluding crossover trials showed a modest -1.05 kg difference favoring glucomannan. The Onakpoya authors concluded that available RCT evidence does not show statistically significant weight loss. Zalewski 2015 (Nutrition) reached a similar verdict for adults - short-term BW reduction with no BMI change.
The lipid evidence is more robust. Ho et al. 2017 in American Journal of Clinical Nutrition (12 trials, 370 participants) found 3g/day konjac glucomannan reduced LDL cholesterol by about 10% (-0.35 mmol/L, roughly -13 mg/dL). That replicates the Sood 2008 lipid findings and uses GRADE methodology.
For constipation, evidence is supportive but smaller than the psyllium evidence base. Glucomannan increases stool bulk and improves transit time at 3-4g/day. It has also been studied in pediatric functional constipation with positive results in some trials.
A specific RCT worth flagging: Keithley et al. 2013 (Journal of Obesity), a 53-participant 8-week trial of glucomannan capsules in overweight adults, found no significant weight loss, hunger, or metabolic difference versus placebo. This is one of the better-controlled standalone trials and it was negative.
Honest summary: glucomannan has a regulator-approved EU weight-claim and a meta-analysis with measurable lipid effects. It also has a 2014 meta-analysis showing no significant weight loss overall and a well-run 2013 RCT showing nothing. Treat it as a modest-effect adjunct that supports satiety and supports lipid markers, not a weight-loss intervention on its own. Safety - particularly esophageal obstruction risk from tablet forms - is the most important practical consideration.
Does It Work? The Evidence
How A-F grades workBody weight reduction (3g/day with energy-restricted diet)
EFSA NDA Panel 2010 authorized Article 13 health claim at 3g/day in three doses; Sood 2008 (n=531) meta-analysis showed -0.79 kg vs placebo; Onakpoya 2014 (J Am Coll Nutr) meta-analysis found no significant overall effect (-0.22 kg, NS); Zalewski 2015 found short-term BW reduction with no BMI change
LDL cholesterol reduction
Ho et al. 2017 Am J Clin Nutr meta-analysis (12 RCTs, n=370): 3g/day konjac glucomannan reduced LDL by -0.35 mmol/L (~10%); Sood 2008 meta-analysis: -16 mg/dL LDL, -19 mg/dL total cholesterol
Constipation and bowel regularity
Several smaller RCTs report improved stool frequency and consistency at 3-4g/day; mechanistically sound as a viscous soluble fiber, though evidence base is smaller than psyllium
Fasting blood glucose reduction
Sood 2008 meta-analysis showed -7 mg/dL fasting glucose vs placebo; smaller and less replicated than the LDL effect
Satiety and appetite suppression before meals
Mechanistic plausibility (viscous gel expands in stomach with water); short-term satiety studies show fullness ratings increase, but translation to durable weight loss is the inconsistent step
Long-term weight maintenance
Most trials are 4-12 weeks; Keithley 2013 (Journal of Obesity, n=53, 8 weeks) found no significant weight loss vs placebo; no long-term maintenance trials
| Grade | Claimed Benefit | Key Studies | Our Verdict |
|---|---|---|---|
| B | Body weight reduction (3g/day with energy-restricted diet) | EFSA NDA Panel 2010 authorized Article 13 health claim at 3g/day in three doses; Sood 2008 (n=531) meta-analysis showed -0.79 kg vs placebo; Onakpoya 2014 (J Am Coll Nutr) meta-analysis found no significant overall effect (-0.22 kg, NS); Zalewski 2015 found short-term BW reduction with no BMI change | Conflicted |
| B | LDL cholesterol reduction | Ho et al. 2017 Am J Clin Nutr meta-analysis (12 RCTs, n=370): 3g/day konjac glucomannan reduced LDL by -0.35 mmol/L (~10%); Sood 2008 meta-analysis: -16 mg/dL LDL, -19 mg/dL total cholesterol | Supported |
| B | Constipation and bowel regularity | Several smaller RCTs report improved stool frequency and consistency at 3-4g/day; mechanistically sound as a viscous soluble fiber, though evidence base is smaller than psyllium | Supported |
| C | Fasting blood glucose reduction | Sood 2008 meta-analysis showed -7 mg/dL fasting glucose vs placebo; smaller and less replicated than the LDL effect | Early Signal |
| C | Satiety and appetite suppression before meals | Mechanistic plausibility (viscous gel expands in stomach with water); short-term satiety studies show fullness ratings increase, but translation to durable weight loss is the inconsistent step | Early Signal |
| D | Long-term weight maintenance | Most trials are 4-12 weeks; Keithley 2013 (Journal of Obesity, n=53, 8 weeks) found no significant weight loss vs placebo; no long-term maintenance trials | Not There Yet |
How to Choose: Forms, Doses & What Matters
Clinical dose: 3g/day split into three 1g doses taken with at least 8oz of water 15-30 minutes before each main meal. This is the dose specified in the EFSA-authorized health claim. Some lipid-lowering trials used 4g/day. Higher doses do not appear to increase efficacy and worsen GI tolerability.
Best forms: Powder mixed into a full glass of water (safest format - hydrates before swallowing), Capsules taken with at least 8oz water per dose (acceptable, but capsule count adds up: 3g/day from 575mg caps = 5-6 capsules), Avoid: solid tablets that can expand in the throat or esophagus before reaching the stomach - the FDA flagged this format in 2002 and several case reports of esophageal obstruction trace back to tablets
Always take glucomannan with a full glass of water (at least 8oz, ideally 12-16oz) per dose. This is non-negotiable. Glucomannan absorbs water at up to 50 times its weight; if it begins to gel before reaching the stomach, it can lodge in the esophagus and cause obstruction. This risk is highest with solid tablet forms, which the FDA flagged in 2002 - powder mixed into water and swallowed promptly, or capsules taken with adequate liquid, are safer formats. The EFSA-authorized dosing protocol is 3g/day split into three 1g doses, taken 15-30 minutes before each main meal with water. This timing lets the fiber begin gelling in the stomach before food arrives, which is the mechanism behind the satiety effect. Start with a lower dose (1-1.5g/day) for the first week and titrate up to 3g/day over 7-14 days. Rapid introduction of viscous fiber causes gas, bloating, and abdominal discomfort in most people. The GI tract adapts within 1-2 weeks. Separate glucomannan from oral medications by at least 2 hours - before or after - to avoid reduced absorption. This is particularly important for levothyroxine, lithium, sulfonylureas, and warfarin. Drink additional water throughout the day. Inadequate hydration combined with bulk-forming fiber worsens constipation rather than relieving it. For lipid effects, expect to wait 6-8 weeks before measurable LDL changes appear in blood work. For satiety, the effect is immediate but the translation to weight loss requires concurrent calorie restriction.
Who Should Take Glucomannan?
Adults pursuing modest weight management as part of a calorie-restricted diet who want a satiety aid taken before meals. People with mildly elevated LDL cholesterol looking for a non-pharmacological adjunct - the lipid evidence is more reliable than the weight evidence. People with mild constipation who want a viscous soluble fiber and prefer something other than psyllium. People following low-carb or ketogenic diets who have reduced overall fiber intake.
Who Should Avoid It?
Not for everyone
Side Effects & Safety
Product Scores
9 products scored on dosing accuracy, third-party testing, cost per effective dose, and label transparency.
The Scorecard: 9 Products Compared
Glucomannan Pure Powder 8 oz
NOW Foods$14.99 ÷ 214 days at ~1g/day (0.4 servings × 3g)
The benchmark glucomannan product. Powder format is safer than tablets and more flexible than capsules. The cheapest way to hit the EFSA-authorized 3g/day dose with a quality brand.
Prices checked 2026-05-16. Cost shown is per clinically effective daily dose, not per pill.
Glucomannan 575 mg
NOW Foods$17.99 ÷ 90 days at 1.15g/day (1 serving × 1.15g)
NOW's standard quality at a good price point. Single-ingredient konjac glucomannan with a well-documented brand track record. The capsule-format reference product.
Prices checked 2026-05-16. Cost shown is per clinically effective daily dose, not per pill.
Glucomannan Powder 250g
BulkSupplements
$12.96 ÷ 130 days at 2g/day (1 serving × 2g)
Cost-sensitive bulk pick. Comparable purity to other single-ingredient powders but lighter on independent verification.
Prices checked 2026-05-16. Cost shown is per clinically effective daily dose, not per pill.
Glucomannan Powder 500g
Nutricost$14.95 ÷ 166 days at 3g/day (1 serving × 3g)
Strong value bulk powder. Comparable to BulkSupplements at slightly higher per-day cost but with longer shelf supply per bag.
Prices checked 2026-05-16. Cost shown is per clinically effective daily dose, not per pill.
Glucomannan 1,800mg per Serving
Nutricost$15.95 ÷ 89 days at ~1g/day (0.7 servings × 1.8g)
Acceptable capsule option from a high-volume brand. Comparable formulation to NOW Foods at similar pricing with weaker quality verification.
Prices checked 2026-05-16. Cost shown is per clinically effective daily dose, not per pill.
Glucomannan 600mg
Solaray
$16.99 ÷ 61 days at ~1g/day (1.6 servings × 0.6g)
Retail-channel option with brand familiarity for in-store shoppers. Comparable quality to NOW Foods at a price premium reflecting distribution channel rather than ingredient differences.
Prices checked 2026-05-18. Cost shown is per clinically effective daily dose, not per pill.
Glucomannan (Konjac Root) 665 mg
Swanson
$9.99 ÷ 45 days at 1.33g/day (2 servings × 0.665g)
Mid-tier capsule option with slightly higher per-capsule dose than NOW Foods (665mg vs 575mg) but comparable overall value.
Prices checked 2026-05-16. Cost shown is per clinically effective daily dose, not per pill.
Herbal Glucomannan from Konjac Root
Nature's Way
$15.99 ÷ 33 days at 1.995g/day (1 serving × 1.995g)
Retail-channel option with Non-GMO Project Verified seal. Higher per-capsule dose than NOW Foods but priced at a retail premium.
Prices checked 2026-05-16. Cost shown is per clinically effective daily dose, not per pill.
Weight-Management Fiber Supplement (Glucomannan)
Lipozene
$19.99 ÷ 8 days at 3g/day (2 servings × 1.5g)
The heavily-marketed TV brand. Active ingredient is identical to NOW Foods or BulkSupplements glucomannan at a substantial price premium driven by marketing spend rather than ingredient differences. If you want glucomannan, buy generic.
Prices checked 2026-05-16. Cost shown is per clinically effective daily dose, not per pill.
Full Comparison
| Category | Glucomannan Pure Powder 8 oz NOW Foods | Glucomannan 575 mg NOW Foods | Glucomannan Powder 250g BulkSupplements | Glucomannan Powder 500g Nutricost | Glucomannan 1,800mg per Serving Nutricost | Glucomannan 600mg Solaray | Glucomannan (Konjac Root) 665 mg Swanson | Herbal Glucomannan from Konjac Root Nature's Way | Weight-Management Fiber Supplement (Glucomannan) Lipozene |
|---|---|---|---|---|---|---|---|---|---|
| Brand Score | 90/100Winner | 88/100 | 84/100 | 83/100 | 82/100 | 80/100 | 79/100 | 78/100 | 52/100 |
| Dosing & Form | 24/25Winner | 22/25 | 24/25 | 24/25 | 22/25 | 20/25 | 20/25 | 20/25 | 14/25 |
| Purity | 21/25Winner | 21/25 | 17/25 | 17/25 | 18/25 | 19/25 | 18/25 | 19/25 | 14/25 |
| Value | 24/25 | 23/25 | 25/25Winner | 24/25 | 22/25 | 19/25 | 20/25 | 18/25 | 8/25 |
| Transparency | 21/25 | 22/25Winner | 18/25 | 18/25 | 20/25 | 22/25 | 21/25 | 21/25 | 16/25 |
| Cost/Day | $0.07Winner | $0.20 | $0.10 | $0.09 | $0.18 | $0.28 | $0.22 | $0.48 | $2.66 |
| Dose/Serving | 3g | 1.15g | 2g | 3g | 1.8g | 0.6g | 0.665g | 1.995g | 1.5g |
| Form | konjac glucomannan powder | vegetable capsule | konjac glucomannan powder | konjac glucomannan powder | vegetable capsule | vegetable capsule | capsule | vegan capsule | capsule |
| Third-Party Tested | ✓ Yes | ✓ Yes | No | No | No | No | No | ✓ Yes | No |
| Proprietary Blend | No | No | No | No | No | No | No | No | No |
Frequently Asked Questions
Does glucomannan actually work for weight loss?
The honest answer is: modestly, sometimes, and probably less than the marketing suggests. Sood et al.'s 2008 meta-analysis of 14 trials (n=531) found a 0.79 kg weight reduction versus placebo at clinical doses. But Onakpoya et al.'s 2014 meta-analysis (Journal of the American College of Nutrition) found no statistically significant overall effect across 8 trials (-0.22 kg, 95% CI -0.62 to 0.19). A sensitivity analysis excluding crossover trials showed -1.05 kg, but the authors' headline conclusion was that available RCTs do not show statistically significant weight loss. EFSA approved a body-weight reduction health claim at 3g/day in three divided doses with water before meals in the context of an energy-restricted diet - but that claim specifically requires concurrent calorie restriction. If you want a weight-loss intervention, glucomannan is a weak adjunct, not a primary tool. The lipid evidence is more reliable than the weight evidence.
Is glucomannan dangerous? I have heard about choking.
The choking and esophageal obstruction risk is real but format-dependent. The FDA took action against konjac confectionery products in 2002, and several published case reports describe esophageal obstruction from glucomannan diet tablets that expanded before being fully swallowed. The risk is highest with solid tablet forms because the tablet can lodge in the esophagus and absorb water locally, swelling into a gel plug. Powder mixed into a full glass of water and swallowed promptly, or capsules taken with at least 8oz of water, are significantly safer. The safety rule is simple: always take glucomannan with substantial water, never take tablets, and do not take it lying down or just before sleep. People with swallowing difficulties or esophageal strictures should avoid glucomannan entirely.
What's the difference between glucomannan and psyllium husk?
Both are viscous soluble fibers with overlapping mechanisms, but the evidence bases differ significantly. Psyllium husk has an FDA-approved health claim for heart disease risk reduction, sits in AGA clinical practice guidelines for chronic constipation, and has been studied in over 20 randomized trials for LDL cholesterol alone. Glucomannan has an EFSA Article 13 weight-loss claim (which psyllium does not) and supportive lipid meta-analyses, but the trial base is smaller and the weight-loss evidence is more contested. For LDL cholesterol or constipation, psyllium is the better-evidenced choice. For satiety before meals as part of a calorie-restricted diet, glucomannan has the more specific regulatory authorization. They are not redundant - psyllium is cheaper and has stronger data; glucomannan is more concentrated per gram and has more pronounced satiety effects.
What is Lipozene and is it different from regular glucomannan?
Lipozene is a heavily-marketed glucomannan product manufactured by Obesity Research Institute. The active ingredient is glucomannan - the same fiber sold by NOW Foods, Solaray, BulkSupplements, and dozens of other brands at a fraction of the price. The marketing positions it as a unique weight-loss product, but it is not. In 2005, the FTC required Obesity Research Institute to pay $1.5 million in consumer redress over deceptive marketing claims related to an earlier product. The underlying glucomannan ingredient is safe when used correctly, but the price premium relative to generic glucomannan reflects marketing spend, not a different ingredient.
What dose of glucomannan do I need for weight loss?
The dose specified in the EFSA-authorized health claim is 3g/day, split into three 1g doses, each taken with at least one to two glasses of water 15-30 minutes before a main meal, in the context of an energy-restricted diet. Some lipid-lowering trials used 4g/day. Going above 4g/day does not increase efficacy in the available data and worsens GI side effects (gas, bloating, loose stools). For practical conversion: a typical 575mg capsule contains about 0.575g, so 3g/day means roughly 5-6 capsules per day, split before meals. Powder is more dose-flexible - measure 1g per serving.
How long until I see results?
For satiety, the effect is immediate - you feel fuller after a meal taken with glucomannan. For weight, trials typically run 4-12 weeks and show modest effects; expect 1-3 kg over 8-12 weeks at best, and only when combined with calorie restriction. For LDL cholesterol, expect 6-8 weeks before measurable changes appear in blood work. Trials longer than 12 weeks are scarce, so long-term maintenance effects are unknown.
Can I take glucomannan with my medications?
Separate glucomannan from oral medications by at least 2 hours in either direction. The viscous gel can delay or reduce absorption of drugs including levothyroxine, lithium, warfarin, sulfonylureas and other oral diabetes medications, oral contraceptives, and any drug with a narrow absorption window. People with diabetes on glucose-lowering medication should monitor blood sugar more carefully, as glucomannan can additively lower glucose. If you take multiple daily medications, this separation requirement can be logistically inconvenient and worth weighing against the modest expected benefit.
Related Reading
Sources
- EFSA Panel on Dietetic Products, Nutrition and Allergies (NDA). Scientific Opinion on the substantiation of health claims related to konjac mannan (glucomannan) and reduction of body weight, and others, pursuant to Article 13(1) of Regulation (EC) No 1924/2006. EFSA Journal. 2010;8(10):1798.
- Sood N, Baker WL, Coleman CI. Effect of glucomannan on plasma lipid and glucose concentrations, body weight, and blood pressure: systematic review and meta-analysis. Am J Clin Nutr. 2008;88(4):1167-1175.
- Onakpoya I, Posadzki P, Ernst E. The efficacy of glucomannan supplementation in overweight and obesity: a systematic review and meta-analysis of randomized clinical trials. J Am Coll Nutr. 2014;33(1):70-78.
- Ho HVT, Jovanovski E, Zurbau A, et al. A systematic review and meta-analysis of randomized controlled trials of the effect of konjac glucomannan, a viscous soluble fiber, on LDL cholesterol and the new lipid targets non-HDL cholesterol and apolipoprotein B. Am J Clin Nutr. 2017;105(5):1239-1247.
- Keithley JK, Swanson B, Mikolaitis SL, et al. Safety and efficacy of glucomannan for weight loss in overweight and moderately obese adults. J Obes. 2013;2013:610908.
- Zalewski BM, Chmielewska A, Szajewska H. The effect of glucomannan on body weight in overweight or obese children and adults: a systematic review of randomized controlled trials. Nutrition. 2015;31(3):437-442.e2.
- Keithley J, Swanson B. Glucomannan and obesity: a critical review. Altern Ther Health Med. 2005;11(6):30-34.
- Vanderbeek PB, Fasano C, O'Malley G, Hornstein J. Esophageal obstruction from a hygroscopic pharmacobezoar containing glucomannan. Clin Toxicol (Phila). 2007;45(1):80-82.
- U.S. Food and Drug Administration. Center for Food Safety and Applied Nutrition Enforcement Story 2002 - Action against konjac mini-cup gel candies posing choking hazard.
- Federal Trade Commission. Settlement with Obesity Research Institute LLC over deceptive weight-loss claims (Lipozene/MetaboTrim). 2005.
FDA Disclaimer: These statements have not been evaluated by the Food and Drug Administration. The products discussed on this page are not intended to diagnose, treat, cure, or prevent any disease. Always consult with a qualified healthcare professional before starting any supplement regimen.