The impact of supplementation with dietary fibers on weight loss: A systematic review of randomised controlled trials

The prevalence of excess body weight has significantly increased, with recent estimates suggesting 1.9 billion people are overweight or obese worldwide. While intake of dietary fiber (mainly from plant-based foods) is associated with improved weight management over time, it is uncertain whether dietary fiber isolates will benefit weight loss. The present study aimed to systematically assess the current evidence that dietary fiber supplementation can impact on weight loss in overweight adults. Blinded, randomised-controlled trials were retrieved from Scopus and Cochrane Central Register of Controlled Trials databases. Studies with free-living, overweight adult participants and fibre supplementation in various forms (i.e. as pills, capsules or powder mix formats) were included. A total of 32 trials were identified that met these criteria. Meta-analysis of statistically pooled data for chitosan (n=6) found significant increases in weight loss (effect size −0.42, 95% confidence interval: −0.81 to −0.03, P<0.001) in treatment groups compared with control groups. For glucomannan (n=5), non-significant difference was found (effect size −0.58, 95% confidence interval: −1.52 to 0.35, P<0.001). Risk of bias within included studies appeared to be low with mean scores of >3 on the Jadad scale and 13 studies scoring the highest possible value. Evidence on the potential impact of supplementation with other fibre types on weight loss was limited by a low number of studies and varied methodological approaches. Further research is recommended to explore these underlying issues to improve the paucity of evidence. A number of elements of study design should also be carefully considered in future work.