The effect of glucomannan on body weight in overweight or obese children and adults: a systematic review of randomized controlled trials

Objective: Glucomannan (GM), a soluble fiber derived from the plant Amorphophallus konjac, is marketed as being helpful in reducing body weight. However, the data supporting this claim are scarce. The aim of this review was to systematically evaluate the effects of GM on body weight (BW) and body mass index (BMI) in otherwise healthy obese or overweight children and adults.

Methods: MEDLINE, EMBASE, CENTRAL, and Google Scholar databases were systematically searched up to June 2014 for randomized controlled trials (RCTs) assessing the effectiveness of GM versus placebo. The primary outcome measures were BW and BMI.

Results: Six eligible RCTs, only one of which performed in children, were included. In adults, three RCTs reported a significant reduction in BW in the GM group compared with the control group at the following different points during the intervention: At week 2 (mean difference [MD], 0.21 kg; 95% confidence interval [CI], 0.13-0.29); at week 4 (MD, 2.04; 95% CI, 0.52-3.56); at week 5 (MD, 1.3; 95% CI, 0.89-1.71); and at week 8 (MD, 3.17; 95% CI, 1.29-5.05). Only one RCT reported a beneficial effect at more than one point. None of the RCTs reported a favorable effect of GM on BMI.

Conclusions: In otherwise healthy overweight or obese adults, there is some evidence that in the short term GM may help to reduce BW, but not BMI. Data in children are too limited to draw any conclusions.