Glucomannan: can this natural supplement help you lose weight?
Reviewed by Felix Gussone, MD, Ro,
Written by Gina Allegretti, MD
last updated: Jan 21, 2022
3 min read
Here's what we'll cover
If you’ve ever been advised to live healthier through nutrition, one thing you’ll hear time and again is to get enough fiber. There are many good reasons for this. Having adequate fiber in your diet helps regulate cholesterol, promotes bowel health, and helps decrease body weight.
Konjac glucomannan is a rich source of fiber available as a food additive and dietary supplement. It has a multitude of purported benefits, including shedding pounds. Some research has examined glucomannan supplements for type 2 diabetes, as many people with this condition may benefit from weight loss. But what does the science say?
Weight loss
Get access to GLP-1 medication (if prescribed) and 1:1 support to meet your weight goals
What is glucomannan?
Glucomannan, or konjac glucomannan, is a dietary fiber from the Amorphophallus konjac (elephant yam) plant. Like other types of dietary fiber, glucomannan is found in some of the things we eat. Dietary fibers are nondigestible carbohydrates, meaning they remain basically intact through the digestive system and don’t contribute calories to food (Miketinas, 2019).
So why would we eat something that we can’t digest? You might be surprised to learn that you don’t need to absorb glucomannan to reap its health benefits. Here are some of the things glucomannan can help do for you.
Can glucomannan help you lose weight?
When you take glucomannan supplements, they mix with liquid in your stomach and intestines. This forms a gel in your stomach, which makes you feel full and slows down the passage of food. Studies suggest this can help regulate body weight (Behera, 2016).
One clinical study demonstrated that glucomannan––in conjunction with a balanced, low-calorie diet––helped people with obesity lose weight. Those who took the supplement lost more weight than individuals in the placebo group, even though both groups consumed fewer calories (Bjerketvedt, 2005).
However, not all studies have come to the same conclusion. Some data has found glucomannan helps reduce body weight, but does not improve your body mass index (BMI). A review of research reported that glucomannan does not significantly reduce body weight, although some people did lose a small amount (Onakpoya, 2014; Zalewski, 2015).
Other benefits of glucomannan
Dietary fiber is an important part of bowel health and science shows it’s beneficial for people living with diabetes, obesity, high cholesterol, and constipation.
Reduce cholesterol
Some types of dietary fiber can help lower cholesterol, especially LDL and triglycerides. LDL is linked to conditions like heart disease. A review of 12 clinical trials demonstrated that glucomannan helped lower LDL cholesterol levels in adults and children (Ho, 2017).
Lower blood sugar
Many people with type 2 diabetes have high blood sugar levels because their bodies don’t respond appropriately to the hormone insulin. Individuals with diabetes are at higher risk for cardiovascular disease, including heart attacks and stroke.
So, how exactly can dietary fiber lower blood sugar levels? Like other forms of dietary fiber, glucomannan slows down the speed food travels through the digestive tract, which decreases the amount of glucose absorbed by the intestines. Since you feel full for longer, it can help reduce body weight, which in turn improves symptoms of diabetes.
It also helps regulate insulin in people with type 2 diabetes. One clinical trial demonstrated that glucomannan balanced glucose and insulin levels even in people with borderline results on their diabetes tests (Yoshida, 2020; Shah, 2015).
Relieve constipation
Dietary fiber makes stool softer, bulkier, and easier to pass, which is why researchers have studied glucomannan as a possible treatment for constipation.
One clinical trial showed that glucomannan significantly improved symptoms of constipation in adults. Those that took supplements had softer, more frequent bowel movements.
Glucomannan also acted as a prebiotic in this group, meaning it promoted the growth of healthy bacteria in the intestines. Another study found that glucomannan significantly improved constipation symptoms in pregnant people (Janani, 2018; Chen, 2006).
However, some researchers disagree. A review of three small clinical trials found that glucomannan only slightly improved the frequency of bowel movements in children with constipation, and did not significantly help their symptoms overall (Han, 2017).
Glucomannan supplements
Glucomannan is extracted from the root of the konjac plant and used to make oral supplements. It comes in powder, tablet, and capsule forms (Behera, 2016).
There is no FDA-approved dosage for glucomannan supplements. However, most studies have focused on a dosage of 2–4 grams a day.
Potential side effects and risks
Most of glucomannan’s side effects are mild and are related to the gastrointestinal tract. Common ones include diarrhea, stomach upset, burping, and bloating (Wharton, 2019).
Isolated cases have reported more severe side effects, such as a blockage in the intestines or esophagus, although these are uncommon (Jackman, 2018; Vanderbeek, 2007). Several types of candy containing glucomannan gel were recalled by the FDA since they caused choking (FDA, 2002).
Healthcare providers usually recommend adequate dietary fiber intake for people with diabetes, obesity, high cholesterol, and constipation. Supplementation with other sources of fiber like glucomannan might be a helpful addition.
DISCLAIMER
If you have any medical questions or concerns, please talk to your healthcare provider. The articles on Health Guide are underpinned by peer-reviewed research and information drawn from medical societies and governmental agencies. However, they are not a substitute for professional medical advice, diagnosis, or treatment.
Behera, S. S. & Ray, R. C. (2016). Konjac glucomannan, a promising polysaccharide of Amorphophallus konjac K. Koch in health care. International Journal of Biological Macromolecules , 92, 942–956. doi:10.1016/j.ijbiomac.2016.07.098. Retrieved from https://pubmed.ncbi.nlm.nih.gov/27481345/
Birketvedt, G. S., Shimshi, M., Erling, T., & Florholmen, J. (2005). Experiences with three different fiber supplements in weight reduction. Medical Science Monitor , 11 (1), PI5–PI8. Retrieved from https://pubmed.ncbi.nlm.nih.gov/15614200/
Chen, H. L., Cheng, H. C., Liu, Y. J., Liu, S. Y., & Wu, W. T. (2006). Konjac acts as a natural laxative by increasing stool bulk and improving colonic ecology in healthy adults. Nutrition , 22 (11-12), 1112–1119. doi:10.1016/j.nut.2006.08.009. Retrieved from https://pubmed.ncbi.nlm.nih.gov/17027233/
Choi, K. H., Kim, S. T., Bin, B. H., & Park, P. J. (2020). Effect of Konjac Glucomannan (KGM) on the Reconstitution of the Dermal Environment against UVB-Induced Condition. Nutrients, 12 (9), 2779. doi:10.3390/nu12092779. Retrieved from https://pubmed.ncbi.nlm.nih.gov/32932917/
Chua, M., Baldwin, T. C., Hocking, T. J., & Chan, K. (2010). Traditional uses and potential health benefits of Amorphophallus konjac K. Koch ex N.E.Br. Journal of Ethnopharmacology , 128 (2), 268–278. doi:10.1016/j.jep.2010.01.021. Retrieved from https://pubmed.ncbi.nlm.nih.gov/20079822/
Devaraj, R. D., Reddy, C. K., & Xu, B. (2019). Health-promoting effects of konjac glucomannan and its practical applications: A critical review. International Journal of Biological Macromolecules , 126, 273–281. doi:10.1016/j.ijbiomac.2018.12.203. Retrieved from https://pubmed.ncbi.nlm.nih.gov/30586587/
Han, Y., Zhang, L., Liu, X. Q., Zhao, Z. J., & Lv, L. X. (2017). Effect of glucomannan on functional constipation in children: a systematic review and meta-analysis of randomised controlled trials. Asia Pacific Journal of Clinical Nutrition , 26 (3), 471–477. doi:10.6133/apjcn.032016.03. Retrieved from https://pubmed.ncbi.nlm.nih.gov/28429913/
Ho, H., Jovanovski, E., Zurbau, A., Blanco Mejia, S., Sievenpiper, J. L., Au-Yeung, F., et al. (2017). 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. The American Journal of Clinical Nutrition , 105 (5), 1239–1247. doi:10.3945/ajcn.116.142158. Retrieved from https://pubmed.ncbi.nlm.nih.gov/28356275/
Janani, F. & Changaee, F. (2018). The effect of glucomannan on pregnancy constipation. Journal of Family Medicine and Primary Care , 7 (5), 903–906. doi:10.4103/jfmpc.jfmpc_168_18. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6259526/
Keithley, J. K., Swanson, B., Mikolaitis, S. L., DeMeo, M., Zeller, J. M., Fogg, L., et al. (2013). Safety and efficacy of glucomannan for weight loss in overweight and moderately obese adults. Journal of Obesity . doi:10.1155/2013/610908. Retrieved from https://pubmed.ncbi.nlm.nih.gov/24490058/
Khan, K., Jovanovski, E., Ho, H., Marques, A., Zurbau, A., Mejia, S. B., et al. (2018). The effect of viscous soluble fiber on blood pressure: A systematic review and meta-analysis of randomized controlled trials. Nutrition, Metabolism, and Cardiovascular Diseases , 28 (1), 3–13. doi:10.1016/j.numecd.2017.09.007. Retrieved from https://pubmed.ncbi.nlm.nih.gov/29153856/
Maia-Landim, A., Ramírez, J. M., Lancho, C., Poblador, M. S., & Lancho, J. L. (2018). Long-term effects of Garcinia cambogia/Glucomannan on weight loss in people with obesity, PLIN4, FTO and Trp64Arg polymorphisms. BMC Complementary and Alternative Medicine , 18 (1), 26. doi:10.1186/s12906-018-2099-7. Retrieved from https://pubmed.ncbi.nlm.nih.gov/29361938/
Miketinas, D. C., Bray, G. A., Beyl, R. A., Ryan, D. H., Sacks, F. M., & Champagne, C. M. (2019). Fiber Intake Predicts Weight Loss and Dietary Adherence in Adults Consuming Calorie-Restricted Diets: The POUNDS Lost (Preventing Overweight Using Novel Dietary Strategies) Study. The Journal of Nutrition, 149(10), 1742–1748. doi: 10.1093/jn/nxz11 . Retrieved from https://pubmed.ncbi.nlm.nih.gov/31174214/
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. doi:10.1080/07315724.2014.870013. Retrieved from https://pubmed.ncbi.nlm.nih.gov/24533610/
Shah, B. R., Li, B., Wang, L., Liu, S., Li, Y., Wei, X., et al. (2015). Health benefits of konjac glucomannan with special focus on diabetes. Bioactive Carbohydrates and Dietary Fibre , 5 (2), 179-187. Retrieved from https://www.sciencedirect.com/science/article/abs/pii/S2212619815000091
U.S. Food and Drug Administration (FDA). (2002). Center for Food Safety and Applied Nutrition 2002. Retrieved on Oct. 12, 2021 from https://www.fda.gov/inspections-compliance-enforcement-and-criminal-investigations/enforcement-story-archive/center-food-safety-and-applied-nutrition-2002
U.S. Food and Drug Administration (FDA). (2020). FDA Grants Citizen Petition on Glucomannan as a Dietary Fiber. Retrieved on Oct. 9, 2021 from https://www.fda.gov/food/cfsan-constituent-updates/fda-grants-citizen-petition-glucomannan-dietary-fiber
Vanderbeek, P. B., Fasano, C., O'Malley, G., & Hornstein, J. (2007). Esophageal obstruction from a hygroscopic pharmacobezoar containing glucomannan. Clinical Toxicology , 45 (1), 80–82. doi:10.1080/15563650601006215. Retrieved from https://pubmed.ncbi.nlm.nih.gov/17357389/
Vuksan, V., Jenkins, D. J., Spadafora, P., Sievenpiper, J. L., Owen, R., Vidgen, E., et al. (1999). Konjac-mannan (glucomannan) improves glycemia and other associated risk factors for coronary heart disease in type 2 diabetes. A randomized controlled metabolic trial. Diabetes Care , 22 (6), 913–919. doi:10.2337/diacare.22.6.913. Retrieved from https://pubmed.ncbi.nlm.nih.gov/10372241/
Wharton, S., Bonder, R., Jeffery, A., & Christensen, R. (2020). The safety and effectiveness of commonly-marketed natural supplements for weight loss in populations with obesity: A critical review of the literature from 2006 to 2016. Critical Reviews in Food Science and Nutrition , 60 (10), 1614–1630. doi:10.1080/10408398.2019.1584873. Retrieved from https://pubmed.ncbi.nlm.nih.gov/30896252/
Yang, D., Yuan, Y., Wang, L., Wang, X., Mu, R., Pang, J., et al. (2017). A Review on Konjac Glucomannan Gels: Microstructure and Application. International Journal of Molecular Sciences, 18 (11), 2250. doi:10.3390/ijms18112250. Retrieved from https://pubmed.ncbi.nlm.nih.gov/29076996/
Yoshida, A., Kimura, T., Tsunekawa, K., Araki, O., Ushiki, K., Ishigaki, H., et al. (2020). Glucomannan Inhibits Rice Gruel-Induced Increases in Plasma Glucose and Insulin Levels. Annals of Nutrition & Metabolism , 76 (4), 259–267. doi:10.1159/000508674. Retrieved from https://pubmed.ncbi.nlm.nih.gov/32659777/
Zalewski, B. M. & Szajewska, H. (2019). No Effect of Glucomannan on Body Weight Reduction in Children and Adolescents with Overweight and Obesity: A Randomized Controlled Trial. The Journal of Pediatrics, 211, 85–91. doi10.1016/j.jpeds.2019.03.044. Retrieved from https://pubmed.ncbi.nlm.nih.gov/31036412/
How we reviewed this article
Current version
Gina Allegretti, MD
Felix Gussone, MD
About the medical reviewer
