Objective: The increased prevalence of obesity has resulted in the current high popularity of dietary supplements marketed as weight reducing agents. The efficacy of most of these supplements is not established. The soluble fiber, glucomannan, is often recommended for weight loss. The aim of this systematic review is to evaluate the evidence for or against the efficacy of glucomannan in body weight reduction.
Methods: Electronic searches were conducted in Medline, Embase, Amed, and The Cochrane Library. Hand searches of bibliography were also conducted. Outcomes of interest were body weight and body mass index. Studies involving only overweight and/or obese participants were included. Two reviewers independently determined the eligibility of studies and assessed the reporting quality of included randomized controlled trials (RCTs), using the CONSORT and PRISMA guidelines.
Results: Eighteen trials were identified, and 9 were included. There was a variation in the reporting quality of the included RCTs. A meta-analysis (random effect model) of 8 RCTs revealed a nonstatistically significant difference in weight loss between glucomannan and placebo (mean difference [MD]: -0.22 kg; 95% confidence interval [CI], -0.62, 0.19; I(2) = 65%). Adverse events included abdominal discomfort, diarrhea, and constipation.
Conclusion: The evidence from available RCTs does not show that glucomannan intake generates statistically significant weight loss. Future trials should be more rigorous and better reported.