Glucomannan and psyllium have both shown efficacy in promoting weight loss.
Fiber products are commonly used to treat constipation and promote regularity. Fiber can also help with weight loss, improve cholesterol levels and lower the risk for certain diseases. Psyllium and glucomannan are two types of bulking fibers that have proven to be particularly effective in promoting weight loss.
Psyllium is a soluble fiber that comes from a shrublike herb. Several popular brands of fiber supplements use psyllium as the key ingredient. According to the University of Maryland Medical Center, the soluble fiber in psyllium husk can aid in lowering cholesterol. Psyllium is a bulking fiber, which means that when it comes in contact with water it swells up and forms a gel-like mass that helps move waste through the digestive tract. UMMC also notes that psyllium has been used to treat diabetes, constipation, diarrhea, heart disease, high blood pressure, irritable bowel syndrome and obesity.
A 2012 article published in "Obesity Reviews" noted that psyllium is effective in reducing risk factors for metabolic syndrome -- a group of conditions that increases the risk for heart disease, stroke and diabetes. One key risk factor in metabolic syndrome is obesity. According to the review, psyllium can be useful in controlling body weight. A 2010 article published in the "Journal of Clinical Gastroenterology" noted that psyllium husk can have a favorable effect on body-weight reduction, as well as cholesterol and triglyceride levels -- all of which are key factors in lowering the risk for metabolic syndrome.
Glucomannan is a sugar that is derived from the root of the konjac plant. Like psyllium, glucomannan is a soluble bulking fiber. Glucomannan, however, may be effective in even smaller doses than psyllium husk due to the fact that it can swell to 17 times its original size when it comes into contact with water. Glucomannan is also used for treating a variety of conditions including constipation, Type 2 diabetes, obesity, high blood sugar and high cholesterol.
A 2005 review published in "Alternative Therapies in Health and Medicine" noted that glucomannan is a well-tolerated supplement that has resulted in significant weight loss in obese and overweight subjects in various studies. Glucomannan was used in doses of 2 to 4 grams per day in these studies. A study published in 2005 in "Medical Science Monitor" tested three fiber supplements for weight reduction. The result was that glucomannan was able to reduce weight in healthy, overweight individuals, whereas the other supplements were not able to promote any additional weight loss.