Glucomannan (GM) is a soluble, fermentable, and highly viscous dietary fiber derived from the root of the elephant yam or konjac plant, which is native to Asia. Preliminary evidence suggests that GM may promote weight loss. This review summarizes studies using GM for weight loss as well as studies investigating its mechanisms of action. At doses of 2-4 g per day, GM was well-tolerated and resulted in significant weight loss in overweight and obese individuals. There is some evidence that GM exerts its beneficial effects by promoting satiety and fecal energy loss. Additionally, GM has been shown to improve lipid and lipoprotein parameters and glycemic status. Further investigation of safety, efficacy, and mechanisms of action is needed to determine whether GM can help to decrease the high prevalence of overweight and obesity in the United States.