Glucomannan: A Powerful Weight Loss & Health-Promoting Nutrient


Getting enough fiber in our diet has always been a critical component for good overall health. Of the two types of plant fiber: soluble and insoluble, both offer differing and unique benefits, but it is the former that is of key interest here. Soluble fiber exists in foods such as oats, beans, barley, certain fruits and vegetables, and of course, the most powerful of them all? glucomannan!

The fact that soluble fibers can form a viscous (gel-like) solution when mixed with water results in several very beneficial effects1-3, such as lowering cholesterol levels, regulating blood sugar and insulin levels, decreasing appetite and promoting fat loss. The health benefits are so impressive that the Food and Drug Administration has approved specific fiber claims that can be used on food and supplement product labels.

This article is designed to explore the science, bioactivity and numerous benefits behind this remarkable soluble fiber. In fact, Glucomannan, in its purest, most potent form, delivers a greater array of health benefits than nearly any other single compound available today.

What is Glucomannan?
Glucomannan (Amorphophallus konjac) is unique among soluble fibers. Its most notable characteristic is its tremendous water-holding capacity, up to 105 times its own weight and 200 times its volume. This amazing gel-forming property is due to its large molecular weight, which can be as high as 2 million Daltons, the largest of any soluble fiber in nature.
Water-holding capacity is a function of soluble fiber’s viscosity, which is commonly perceived as “thickness,” or resistance to pouring. Glucomannan has the highest viscosity of any known soluble fiber. And that water-holding, gel-forming power is the key to its unprecedented success as a health promoter.

The Importance of High-Viscosity Glucomannan
One of the most pivotal distinctions to know and understand about this compound is that glucomannan works physically (by forming a gel) not enzymatically or chemically like other nutrients and drugs that promote weight loss. It delays stomach emptying, triggering satiety (a feeling of fullness) that can be helpful in trying to lose and maintain weight. The viscosity of glucomannan is magnitudes higher than all other soluble fibers, including guar gum and pectin. Research has shown that in head-to-head comparisons, glucomannan has greater gel volume and viscosity properties compared to other soluble fibers4, and therefore appears to be the ideal soluble fiber for promoting weight and fat loss, suppressing appetite, controlling glucose and insulin surges, and lowering cholesterol.

But be advised, there are glaringly different qualities of glucomannan, with varying levels of viscosity. Researchers in Japan have clearly shown that high-viscosity glucomannan is much more effective at reducing the increase in blood sugar to a meal compared to low-viscosity glucomannan5. This particular effect is due to a decrease in gastric emptying time. Other experiments clearly showed that glucomannan reduced cholesterol levels by increasing cholesterol excretion lost though bile.

Small Amounts Lead to Big Health Benefits
A number of placebo-controlled studies have shown that relatively small amounts of glucomannan (1 to 4 grams per day) enhances weight loss6-11. These effects are seen in studies that involved diets that were either calorically restricted or free-living where no guidance to restrict calories was provided. In a landmark study published over two decades ago, it was shown that obese subjects who were provided 3 grams of highly purified glucomannan per day for 8 weeks lost a significant amount of weight and experienced significant improvements in total and LDL cholesterol6. All the subjects in this study were specifically instructed not to change their normal eating and exercise patterns and so it was not surprising that the placebo group experienced no changes in weight or cholesterol.

In another double-blind, placebo-controlled study, overweight subjects who were provided 3 grams of highly purified glucomannan per day for 8 weeks lost more than 8 pounds without any instructions to modify their diet7. That’s a pound a week, without changing their diet–simply remarkable! This notable clinical trial had the strength of using a cross-over study design (all subjects participated in both the glucomannan and a placebo trial), which removes the problem of potential differences between groups because each subject serves as their own control.

In yet another key study, this time of overweight patients with high blood pressure, glucomannan (3 grams per day) was provided to a group that restricted calories and a group with no caloric restriction, both lost more weight than a placebo group8. Weight loss after 4 weeks was slightly higher in the glucomannan group that also restricted calories (-5.3 pounds) compared to the unrestricted group (-3 pounds). In a follow-up study, these authors again showed superior weight loss and decreased cholesterol levels after 8 weeks of glucomannan combined with a caloric restriction9. Furthe-rmore, in a study of obese children provided highly-purified Shimizu glucomannan from Japan and prescribed a balanced diet, experienced weight loss, and cholesterol and triglyceride decreases that were significantly greater than a control group10. Other studies testing the combination of glucomannan with a reduced calorie diet show greater weight loss than even caloric restriction alone11,12.

These, and other equally extraordinary studies clearly show the potential of high-quality glucomannan to cause a spontaneous decrease in food consumption and accompanying weight loss and drops in cholesterol levels. Considering that most people regain weight because they cannot maintain caloric restriction over the long-term, the fact that glucomannan reduces food intake on the subject’s own volition is a major advantage over other diet approaches that rely on will power. Further, glucomannan works through its high viscosity and gel-forming properties, not the sympathetic nervous system like other weight loss stimulants. Glucomannan is believed to promote feelings of fullness by forming a gel in the stomach, which in turn sends signals to the appetite center in the brain that control hunger and satiation.

More Great News
Glucomannan has other major health benefits that are independent of its potent effects on weight loss. A large number of studies have consistently shown that glucomannan taken prior to, or with a meal, significantly reduces the glucose and insulin response by as much as one-half 5,12-17. This again is due to its powerful bulk-forming properties in the stomach, a function of the viscosity of the glucomannan product. Only high-viscosity glucomannan, however, has the potent glucose-lowering effects with less-viscous versions having less of an effect or no effect at all5.
In addition to effecting weight loss and glucose and insulin levels, glucomannan has been shown to have significant and consistent cholesterol-lowering effects in numerous clinical studies18-25. The effects are potent even with small doses (<4 grams per day). For example, in a recent randomized, placebo-controlled, double-blind, cross-over clinical trial in diabetic subjects, glucomannan (3.6 grams per day) decreased LDL-cholesterol by 21%, improved the total cholesterol to HDL-cholesterol ration by 16%, and decreased the fasting and 2-hour glucose levels by 23% and 28%, respectively24. The mechanism of this potent lipid-lowering effect of glucomannan has been investigated in some eloquent animal and human studies. Most evidence indicates that glucomannan interferes with cholesterol absorption or enhances cholesterol excretion lost through bile. This loss of cholesterol in bile would in turn need to be replaced by cholesterol from the blood and therefore results in decreased blood cholesterol levels. Importantly, glucomannan does not decrease fat absorption22, which is a positive aspect because malabsorption of fat would be associated with potential undesired side effects.

Glucomannan is a highly viscous soluble fiber that has been widely used in the Orient for hundreds of years. An impressive amount of research has shown that small amounts of glucomannan administered before or during meals leads to significant weight loss and consistent reductions in appetite, cholesterol, glucose, and insulin. These effects have been observed in a variety of healthy and clinical populations. No serious side effects have been documented in any of the studies of glucomannan. It is evidence-based, well-tolerated, stimulant-free, and easy to incorporate into the diet.

Although glucomannan has been shown to effectively enhance weight loss, the beneficial effects on glucose and insulin and its lipid-lowering properties are not dependent on losing weight. Thus the therapeutic applications of glucomannan extend well beyond weight loss to include individuals with glucose and insulin disturbances (e.g., insulin resistance, glucose intolerance, and type II diabetes), cholesterol and other lipid disorders, and those with combinations of these disorders such as metabolic syndrome. Of course, anyone suffering from any of these disorders or any other medical conditions should consult with their physician prior to using glucomannan or any other dietary supplement.

The weight loss and health-promoting effects of glucomannan are directly coupled to its viscosity. The superiority of highly viscous glucomannan over less viscous and less pure products is clear.

Reposted from

One Response to “Glucomannan: A Powerful Weight Loss & Health-Promoting Nutrient”

  1. Rob Says:

    Thank you for the very clear and detailed articled on glucomannan. I am currently on my first bottle of glucomannan. My soluble fiber is low, and glucomannan is great and it agrees with my system, much better than Metamucil.

Leave a Reply

XHTML: You can use these tags: <a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <strike> <strong>