© 2020 Elsevier LtdObjective: There are conflicting reports about the effect of glucomannan in the weight control which may be due to the variations in the intervention dose, participants, sample sizes, study durations and overall methodological quality. The present systematic review and meta-analysis were conducted to investigate the effects of glucomannan on weight loss in overweight and obese adults. Methods: Relevant studies, published up to April 2020, were searched through PubMed/Medline, Scopus. All randomized clinical trials investigating the effect of glucomannan supplementation on weight loss were included. Results: Out of 134 citations, 6 trials that enrolled 225 subjects were included. glucomannan resulted in significant reduction in weight (Weighted mean differences (WMD): −0.96 kg; 95% CI: −1.81 to −0.11, P = 0.02) (I2 = 88.1%, P < 0.001). Additionally, there was considerable effect on body weight in female (WMD: −1.86, 95% CI: −2.88, −0.84, P < 0.001), studies with ≤30 participants (WMD: −1.67, 95% CI: −3.09, −0.25, P = 0.02) and ≤8 weeks duration weeks (WMD: −1.34, 95% CI: −2.45, −0.23, P = 0.01). Conclusion: In this meta-analysis we found a significant reduction in body weight following glucomannan consumption in overweight and obese adults. Therefore, the recommendation on glucomannan supplementation could be a practical approach to reduce body weight in overweight and obese adults. Further clinical trials assessing the effect of glucomannan on body composition are needed and a validated methodology for measuring that should be used.