Glucomannan: can this natural supplement help you lose weight?

Felix Gussone, MD - Contributor Avatar

Reviewed by Felix Gussone, MD, Ro, 

Written by Gina Allegretti, MD 

Felix Gussone, MD - Contributor Avatar

Reviewed by Felix Gussone, MD, Ro, 

Written by Gina Allegretti, MD 

last updated: Jan 21, 2022

3 min read

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?

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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.  


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.

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How we reviewed this article

Every article on Health Guide goes through rigorous fact-checking by our team of medical reviewers. Our reviewers are trained medical professionals who ensure each article contains the most up-to-date information, and that medical details have been correctly interpreted by the writer.

Current version

January 21, 2022

Written by

Gina Allegretti, MD

Fact checked by

Felix Gussone, MD

About the medical reviewer

Felix Gussone is a physician, health journalist and a Manager, Medical Content & Education at Ro.

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