Konjac is one of the very rare ingredients to benefit from a European health claim (EFSA) on weight loss. This regulatory status is based on rigorous clinical trials: Onakpoya 2014 meta-analysis in J Am Coll Nutr and Sood 2008 in Am J Clin Nutr. We detail here the exact mechanism, the validated dose (3 g/day), the optimal protocol and the concrete results to expect over 8 to 12 weeks. Spoiler: konjac is not a miracle product, it is a scientifically validated tool to facilitate adherence to a calorie-restricted diet.
Pure Konjac - 120 capsules
Pure glucomannan extracted from the root ofAmorphophallus konjac, dosed at the EFSA validated value for weight loss as part of a calorie-restricted diet.
View Pure Konjac →EFSA claim Q-2009-00373 states that 3 g of glucomannan per day, in 3 doses before meals with 250 mL of water, contributes to weight loss in a calorie-restricted diet. The Onakpoya 2014 meta-analysis in J Am Coll Nutr (8 RCTs, n=308) confirms significant weight loss vs placebo. Sood 2008 in Am J Clin Nutr (14 studies, n=531) documents -0.79 kg on average. Modest but reproducible effect, provided it is combined with a calorie deficit of 300 to 500 kcal/day. Recommended course: 8 to 12 weeks.
The EFSA claim Q-2009-00373 explained
The European Food Safety Authority (EFSA) validated in 2010 the claim: "Glucomannan, as part of a calorie-restricted diet, contributes to weight loss." Official reference: Q-2009-00373, integrated into EU regulation 432/2012. Validated dose: 3 g/day divided into 3 doses with a large glass of water.
The EFSA is the independent European agency that evaluates health claims on foods. For a claim to be validated, the scientific panel requires a high level of clinical evidence : randomized controlled trials, reproducible effect, plausible mechanism. Many popular "weight loss" ingredients have not obtained this validation (garcinia, raspberry ketone, green coffee). Konjac is among the rare ones to have received it.
The official wording requires three cumulative conditions:
- Minimum dose of 3 g of glucomannan per day, divided into 3 doses of 1 g before main meals
- Ingestion with 1 to 2 glasses of water per dose (minimum 250 to 500 mL)
- Associated calorie-restricted diet : this is the critical condition, konjac alone does not cause weight loss
How konjac helps with weight loss
Three main mechanisms: (1) gastric distension via glucomannan which absorbs 50 times its weight in water and swells in the stomach, (2) slowed gastric emptying which prolongs satiety and smooths blood sugar levels, (3) production of short-chain fatty acids by colonic fermentation which modulates satiety via PYY and GLP-1.
Mechanical gastric distension
Taken before a meal with a large glass of water, glucomannan forms in the stomach a highly viscous gel that occupies considerable volume. Gastric mechanoreceptors signal to the brain, via the vagus nerve, that the stomach is full. The sensation of hunger diminishes and the meal is spontaneously less substantial.
Slowing of gastric emptying
The gel's viscosity slows the passage of food bolus into the intestine. Consequences: prolonged satiety for several hours after meals, and smoothing of the postprandial glycemic peak. Fewer cravings 2 to 4 hours after meals, which reduces spontaneous snacking.
Colonic fermentation and short-chain fatty acids
Undigested glucomannan reaches the colon where it is fermented by the microbiota, producing acetate, propionate and butyrate. These molecules activate FFAR2/FFAR3 receptors which modulate the secretion of satiety hormones PYY and GLP-1. A more lasting long-term effect.
What meta-analyses say
Meta-analysis Onakpoya 2014 in J Am Coll Nutr (8 RCT, n=308): significant weight loss in the glucomannan group vs placebo. Meta-analysis Sood 2008 in Am J Clin Nutr (14 studies, n=531): -0.79 kg on average, modest but reproducible. The effect is more pronounced in overweight subjects combining glucomannan and caloric deficit.
The meta-analysis by Onakpoya et al. 2014 published in J Am Coll Nutr remains the reference for evaluating the effect of glucomannan on weight loss. It grouped together 8 randomized controlled trials in 308 overweight or obese adult subjects. The conclusion: glucomannan leads to significant weight loss compared to placebo, especially in studies combining supplementation and moderate caloric deficit.
The larger meta-analysis by Sood et al. 2008 in Am J Clin Nutr had previously grouped 14 studies (n=531) and documented an average weight loss of 0.79 kg (95% CI: -1.53 to -0.05) vs placebo. Modest in absolute value, but reproducible and statistically significant, which justified EFSA validation. For comparison, orlistat (weight loss medication) leads to an average of -2.9 kg over 1 year, but with significant side effects.
The recent study Citarrella 2024 in Nutrients confirmed the benefit of glucomannan supplementation (4 g/day) on weight, BMI and several metabolic markers in subjects with metabolic syndrome, over 16 weeks.
The effective dose: 3 g/day, how to achieve it
EFSA Dose: 3 g of glucomannan per day, divided into 3 doses of 1 g before each main meal, with 250 to 500 mL of water per dose. With capsules dosed at 500 mg, this represents 6 capsules per day (2 before breakfast, 2 before lunch, 2 before dinner).
Strict adherence to this dose is essential: supplementation at 1.5 g/day does not produce a significant effect. The threshold dose of 3 g/day is the one that has been scientifically validated.
Detailed 12-week protocol
Standard protocol: Gradual introduction over 1 week (1 g/day, then 2 g, then 3 g), then maintenance at 3 g/day for 10 to 12 weeks, with moderate caloric deficit (300-500 kcal/day). Break of 2 to 4 weeks before potential resumption.
Week 1: digestive adaptation
Start at 1 g/day before lunch only, with 250 mL of water. Assess digestive tolerance (bloating, gas). If well tolerated, proceed to the next step.
Week 2: dose increase
2 g/day divided into 2 doses (1 g before lunch + 1 g before dinner). Maintain hydration at 250 mL of water per dose.
Weeks 3 to 12: full EFSA dose
3 g/day divided into 3 doses (1 g before each main meal). This is the effective phase, to be maintained for 10 to 12 weeks alongside a moderate low-calorie diet and regular physical activity.
After 12 weeks: break
Break of 2 to 4 weeks to preserve satiety effectiveness (the body gradually adapts). This break is also an opportunity to solidify the new eating habits acquired during the treatment period.
Concrete results to expect
With moderate caloric deficit (300-500 kcal/day) + 3 g of konjac per day, expect 1.5 to 3 kg in the first month, then 0.5 to 1 kg per week over the following 8 weeks. In total, 4 to 8 kg over 12 weeks depending on initial excess weight and protocol adherence.
Phase 1 (weeks 1-2): initial rapid loss
In the first 2 weeks, weight loss is greater (1 to 2 kg/week) but corresponds essentially to water and muscle glycogen loss, typical at the start of a diet. Don't get overly enthusiastic: this is not fat loss.
Phase 2 (weeks 3-8): cruising
Steady loss of 0.5 to 1 kg/week, predominantly fat mass. This is the phase most representative of the true effect of the protocol. The increased satiety from konjac helps maintain the caloric deficit without frustration.
Phase 3 (weeks 9-12): consolidation
Weight loss naturally slows down (0.3 to 0.5 kg/week), the body adapts to its new weight. This is the phase for building lasting habits. Important: do not increase caloric restriction, but consolidate your results.
What not to expect
Konjac is not a miracle product. If the goal is to lose 15 kg in 1 month, that is unrealistic and dangerous. Healthy and sustainable weight loss is between 0.5 and 1 kg per week. Beyond that, the risk of weight regain (yo-yo effect) is very high.
The mistakes that cancel out effectiveness
Optimizations to implement
- Protein-rich breakfast : 25 to 30 g of protein (2 whole eggs or 30 g of whey) to amplify the satiety effect of konjac throughout the morning
- 500 mL of water 30 minutes before each meal : documented effect of -2 kg over 12 weeks according to Dennis 2010 in Obesity
- Moderate physical activity : 150 minutes per week of cardio + 2 strength training sessions to preserve lean mass
- 7-8 hours of sleep : sleep deprivation increases ghrelin and cravings, sabotages your caloric deficit
Frequently Asked Questions
How much weight can you lose with konjac?
The effect is modest and conditioned on a caloric deficit. The Onakpoya 2014 meta-analysis in J Am Coll Nutr shows significant weight loss vs placebo. Sood 2008 in Am J Clin Nutr documents -0.79 kg on average across 14 studies. In practice, konjac helps lose 1 to 3 additional kg per month by facilitating diet adherence, no more.
What is the EFSA validated dose for weight loss?
The validated EFSA claim Q-2009-00373 established in 2010 stipulates that 3 g of glucomannan per day, divided into 3 doses of 1 g before each meal with 250 to 500 mL of water, contributes to weight loss as part of a calorie-restricted diet. This dose is integrated into EU Regulation 432/2012.
How long does it take for konjac to help you lose weight?
The first effects on satiety are noticeable within 3 to 7 days. Significant weight loss is observed after 4 to 6 weeks of treatment with a moderate caloric deficit. Clinical trials that validated the effect are generally 8 to 12 weeks long (Onakpoya 2014).
Does konjac help you lose weight without a diet?
No. The EFSA is very explicit: the weight loss claim applies only as part of a calorie-restricted diet. Without a caloric deficit, konjac's effect on weight remains marginal. Its role is to facilitate diet adherence by reducing hunger.
Konjac or Actifslimming for weight loss?
Both work on different and complementary mechanisms. Konjac: mechanical satiety (appetite suppressant). Actifslimming: thermogenesis, fat oxidation, glycemic stabilization. Combining them via Nutripack' Slimming allows you to leverage the 4 main mechanisms of weight loss.
What weight loss can you expect in 1 month with konjac?
With a moderate caloric deficit (300-500 kcal/day) and 3 g of konjac per day, expect 1.5 to 3 kg in the first month, with some portion being fat mass. Weight loss is faster in the first 2 weeks (water and glycogen loss), then stabilizes to approximately 0.5 to 1 kg per week.
Does konjac help you lose belly fat?
Konjac does not specifically target abdominal fat. It promotes overall weight loss including a proportional reduction in visceral and subcutaneous fat. To target waistline reduction, combine with a moderate caloric deficit, protein at each meal, and physical activity (cardio + strength training).
Does konjac cause weight regain when stopped?
Not directly, but as with any weight loss aid, maintenance depends on the eating habits acquired during treatment. If you return to your previous eating patterns without change, weight regain is likely. Using the treatment period to establish new habits (protein, fiber, water) is essential.
How many konjac capsules per day to lose weight?
To reach the EFSA dose of 3 g/day with capsules dosed at 500 mg of glucomannan, count on 6 capsules divided into 3 doses (2 capsules × 3 times per day, before each main meal). Our Pure Konjac 120 capsules allows for approximately a 20-day treatment at this dose.
Is konjac suitable for everyone to lose weight?
Konjac is suitable for most overweight adults with moderate excess weight. Contraindications: digestive stenosis, severe swallowing disorders, intestinal obstruction, children under 12 years, pregnancy, breastfeeding. If taking medication (levothyroxine, anticoagulants, antidiabetics), consult a physician.
- Glucomannan
- Soluble polysaccharide fiber extracted from the konjac root. Exceptional water absorption capacity (50 times its weight).
- EFSA Claim
- Health claim approved by the European Food Safety Authority following scientific evaluation. Q-2009-00373 = reference code for the weight loss claim.
- Caloric Deficit
- Caloric intake lower than energy requirements. Necessary condition for weight loss. Recommendation: 300 to 500 kcal/day for healthy weight loss.
- Gastric Distension
- Mechanical stretching of the stomach wall, detected by mechanoreceptors and transmitted to the brain via the vagus nerve to signal satiety.
- Yo-Yo Effect
- Rapid weight regain after stopping an overly restrictive diet, often exceeding initial weight. Related to metabolic adaptation and increased ghrelin levels.
- Onakpoya I, et al. 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. DOI: 10.1080/07315724.2014.870013
- 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. DOI: 10.1093/ajcn/88.4.1167
- Citarrella R, et al. Effectiveness of a Food Supplement Based on Glucomannan, D-Chiro-Inositol, Cinnamomum zeylanicum Blume and Inulin in Patients with Metabolic Syndrome. Nutrients. 2024;16(2):249. DOI: 10.3390/nu16020249
- EFSA Panel on Dietetic Products, Nutrition and Allergies. Scientific Opinion on the substantiation of a health claim related to konjac mannan (glucomannan) and reduction of body weight. Q-2009-00373. EFSA Journal. 2010;8(10):1798.
- Commission Regulation (EU) No 432/2012 of 16 May 2012 establishing a list of permitted health claims made on foods.
- Dennis EA, et al. Water consumption increases weight loss during a hypocaloric diet intervention in middle-aged and older adults. Obesity (Silver Spring). 2010;18(2):300-307. DOI: 10.1038/oby.2009.235
