- Health advice
- Mar 29, 2014
Glucomannan is a natural fibre from the konjac plant that may help you feel full, so you eat less. It works best when you also eat well, move your body and drink plenty of water.
In this guide, we explain how glucomannan works and what the research says. We also cover how to take it safely and who should avoid it.
Key takeaways
- Glucomannan soaks up water and turns into a thick gel in your stomach. This may help you feel full on smaller meals.
- The usual dose for weight loss is 3 g a day. Take 1 g before each of your three main meals.[1]
- Studies show it may help a little, with most people losing around 1 kg more than those who did not take it.[2][3]
- It may also help keep cholesterol at healthy levels.[1][6]
- Always take it with a full glass of water (about 250 ml). This helps stop it from getting stuck in your throat.[9]
What is glucomannan?
Glucomannan is a type of fibre that comes from the root of the konjac plant (Amorphophallus konjac). People in China and Japan have eaten konjac for hundreds of years.
Glucomannan is a soluble fibre. This means it mixes with water and turns into a soft gel.
It can soak up a lot of water for its size. That is why only a small amount is needed.
Your body does not break down or absorb glucomannan. It moves through your gut, and the good bacteria in your bowel feed on some of it.
How does glucomannan help with weight loss?
Glucomannan does not burn fat or speed up your metabolism. Instead, it helps you feel full, so it is easier to eat less.
1. It fills you up
When you take glucomannan with water before a meal, it swells in your stomach. You may feel full sooner and eat a smaller serve.
2. It keeps you full for longer
The gel slows down how fast food leaves your stomach. This may help you snack less between meals.
3. It adds fibre with almost no kilojoules
Glucomannan gives your body almost no energy. This makes it an easy way to add fibre while you are cutting back on food.
Does glucomannan really work for weight loss?
Glucomannan may help, but the results are small. It is important to know what to expect before you start.
- European food safety experts (2010): The European Food Safety Authority (EFSA) agreed that 3 g a day may help weight loss. This was for people who were also eating fewer kilojoules.[1]
- Review of 9 studies (2014): This review found glucomannan did not lead to clear weight loss. People who took it lost about the same as people who took a placebo.[2]
- Review of studies (2015): This review found it may help adults lose weight in the short term. It did not seem to help children.[4]
- Review of 6 studies (2020): People who took glucomannan lost about 1 kg more than those who did not. Results were very different from one study to the next.[3]
- Six-month study (2024): Adults who took a fibre mix with glucomannan lost more weight than those on a placebo.[8] The mix also had other fibres, so we can't say glucomannan did it all.
The bottom line: glucomannan is not a magic pill. It can be a handy tool to help you control hunger and serve sizes.
How to take glucomannan
How much you take depends on your goal. This table is based on the amounts used in research.[1]
| Your goal | How much a day | How to take it |
|---|---|---|
| Weight loss | 3 g | 1 g before each main meal, with 1 to 2 glasses of water |
| Healthy cholesterol | 4 g | Spread across the day, with plenty of water |
| Regular bowel movements | Start with 1 g | Slowly add more over 1 to 2 weeks, with extra water |
Mr Vitamins tip: Take glucomannan 15 to 60 minutes before you eat. This gives it time to swell so you feel full when you sit down to your meal.
Tips for taking glucomannan
- Start with a small dose and slowly build up. This can help stop bloating and wind.
- Always take it with at least one full glass of water (about 250 ml).
- Don't take it just before bed or while lying down.
- Take other medicines and supplements at least 2 hours before or after. Fibre can stop them from working as well.
- Always follow the directions on the label, as doses can change between brands.
Other ways glucomannan may help your health
Healthy cholesterol
Glucomannan's gel may trap some of the cholesterol from your food, so less gets into your body. One big review found it lowered LDL ("bad") cholesterol by around 10%.[6]
Another review found it also lowered total cholesterol and blood fats called triglycerides.[5] The dose used for cholesterol is usually 4 g a day.[1]
Healthy blood sugar
Glucomannan slows down how fast your body takes in sugar from food. This may help stop big blood sugar spikes after meals.[7]
If you take medicine for diabetes, talk to your doctor first. Glucomannan may make your blood sugar drop too low.
Regular bowel movements
Glucomannan makes your stools softer and bulkier, which may help if you are a bit blocked up. It also feeds the good bacteria in your gut.
Glucomannan vs psyllium and other fibres
There are many fibre supplements to choose from. Here is how glucomannan compares with some popular options.
| Fibre | Where it comes from | Best for | Good to know |
|---|---|---|---|
| Glucomannan | Konjac root | Feeling full, weight loss, cholesterol | Soaks up lots of water, so you need only a small dose |
| Psyllium husk | Psyllium seeds | Regular bowel movements, cholesterol | Well known for helping constipation |
| Guar gum | Guar beans | Gentle gut support | Often easy on the tummy |
| Inulin | Chicory root | Feeding good gut bacteria | Doesn't form a thick gel and may cause wind |
| Sugarcane fibre | Sugarcane | Adding bulk to stools | Mostly insoluble fibre, so it doesn't form a gel |
Want to know more? Read our guide to sugarcane fibre supplements.
Side effects and safety
Choking warning: Glucomannan swells fast when it touches water. If you don't drink enough water with it, it could swell in your throat or food pipe and cause choking.[9]
Always take it with a full glass of water. Get medical help straight away if you have chest pain, vomiting or trouble swallowing or breathing after taking it.
Common side effects
Most people handle glucomannan well. When you first start, you may notice bloating, wind, a very full tummy or changes to your bowel habits.
These usually settle down after a week or two. Starting with a small dose and drinking lots of water can help.
Who should avoid glucomannan or check with a health professional first?
- People who have trouble swallowing
- People with a narrow food pipe or bowel, or who have had a bowel blockage
- People who take medicine for diabetes
- People who take any regular medicine
- Women who are pregnant or breastfeeding
- Children, unless a health professional says it is OK
Foods that contain glucomannan
You can also get glucomannan from konjac foods like shirataki noodles and konjac rice. You can find them at many supermarkets and Asian grocers.
These foods are very low in kilojoules and make a good swap for pasta or rice. But they usually have less glucomannan than a supplement.
Is there a quick fix for weight loss?
Sadly, there is no quick fix for lasting weight loss. Glucomannan can help you get started, but healthy daily habits are what make the biggest difference.
Try to eat a wide range of whole foods, as the Australian Dietary Guidelines suggest.[10] Women should aim for about 25 g of fibre a day, and men about 30 g.[11]
Healthy habits that help with weight loss
- Protein at every meal: Eggs, fish, chicken, beans and tofu help keep you full.
- Lots of vegetables: Fill half your plate with veggies, especially leafy greens.
- Low-sugar fruit: Berries, kiwifruit and oranges are great choices.
- Healthy fats: Enjoy olive oil, avocado, nuts and seeds in small amounts.
- Water: Drink water all day, especially when you take fibre.
- Move your body: Aim for 150 to 300 minutes of activity like brisk walking each week.[12]
- Sleep and stress: Poor sleep and stress can make you hungrier and cause cravings.
Mr Vitamins recommends
Herbs of Gold Fibre Full & Burn
Fibre Full & Burn combines glucomannan with Svetol® green coffee bean extract. It is made to support weight management alongside a kilojoule-controlled diet and exercise.
Shop the full Herbs of Gold range.
Always read the label and follow the directions for use. If symptoms persist, talk to your health professional. Weight management products work best with a kilojoule-controlled diet and exercise.
Not sure if glucomannan is right for you?
Our qualified naturopaths and nutritionists are here to help you choose the right fibre for your goals. Pop into one of our stores or send us your question online.
Frequently asked questions
How much weight can you lose with glucomannan?
Most studies show people lose around 1 kg more than those who don't take it. You'll get better results if you also eat well and stay active.
When is the best time to take glucomannan?
Take it 15 to 60 minutes before meals with 1 to 2 glasses of water. This gives it time to swell so you feel full before you eat.
How long does glucomannan take to work?
You may feel fuller within the first few days. Most weight loss studies lasted 4 to 12 weeks.
Is glucomannan the same as psyllium?
No, they come from different plants. Glucomannan soaks up much more water, so you need a smaller dose.
Can I take glucomannan with my medicine?
Take other medicines at least 2 hours before or after glucomannan. If you take diabetes medicine or any regular medicine, check with your doctor or pharmacist first.
Is it safe to take glucomannan every day?
Most healthy adults can take it every day if they follow the label and drink plenty of water. Talk to a health professional if you want to take it long term or have a health condition.
Does glucomannan cause bloating?
Some people get bloating or wind when they first start. Starting with a small dose and slowly taking more usually helps.
This article is for general information only. It does not replace advice from your doctor or health professional. Always read the label and follow the directions for use. Supplements should not replace a balanced diet.
References
- EFSA Panel on Dietetic Products, Nutrition and Allergies (2010). Scientific opinion on the substantiation of health claims related to konjac mannan (glucomannan). EFSA Journal, 8(10): 1798.
- Onakpoya I, Posadzki P, Ernst E (2014). The efficacy of glucomannan supplementation in overweight and obesity: a systematic review and meta-analysis of randomized clinical trials. Journal of the American College of Nutrition, 33(1): 70-78.
- Mohammadpour S, et al. (2020). Effects of glucomannan supplementation on weight loss in overweight and obese adults: a systematic review and meta-analysis of randomized controlled trials. Obesity Medicine, 19: 100276.
- Zalewski BM, Chmielewska A, Szajewska H (2015). The effect of glucomannan on body weight in overweight or obese children and adults: a systematic review of randomized controlled trials. Nutrition, 31(3): 437-442.
- Sood N, Baker WL, Coleman CI (2008). Effect of glucomannan on plasma lipid and glucose concentrations, body weight, and blood pressure: systematic review and meta-analysis. American Journal of Clinical Nutrition, 88(4): 1167-1175.
- Ho HVT, et al. (2017). The effect of oral konjac glucomannan on LDL cholesterol and non-HDL cholesterol: a systematic review and meta-analysis of randomized controlled trials. European Journal of Clinical Nutrition, 71: 1135-1141.
- Effects of glucomannan supplementation on type II diabetes mellitus in humans: a meta-analysis (2023). Nutrients, 15(3): 601.
- The impact of glucomannan, inulin and psyllium supplementation (Soloways) on weight loss in adults with FTO, LEP, LEPR and MC4R polymorphisms: a randomized, double-blind, placebo-controlled trial (2024). Nutrients, 16(4): 557.
- Health Canada (2010). Natural health products containing glucomannan may cause serious choking if used with insufficient fluid. Advisory RA-110003825.
- National Health and Medical Research Council (2013). Australian Dietary Guidelines. Canberra: NHMRC.
- National Health and Medical Research Council. Nutrient Reference Values for Australia and New Zealand: Dietary Fibre. eatforhealth.gov.au.
- Australian Government Department of Health and Aged Care. Physical activity and exercise guidelines for adults (18 to 64 years). health.gov.au.
- Keithley J, Swanson B (2005). Glucomannan and obesity: a critical review. Alternative Therapies in Health and Medicine, 11(6): 30-34.
Related Articles
Recently Viewed
- ${ variant.price | currencyFromCents } | ${ variant.title } ${ variant.price | currency } | ${ variant.title }
