Effect of Viscous Soluble Fibres on Body Weight

Background: Obesity is a global pandemic and is an independent risk factor for chronic disease. Dietary intervention is an essential component of obesity management. Observational studies show an inverse relationship between dietary fibres and body weight. Therefore, supplements of dietary fibres have the potential to facilitate weight reduction, possibly on the basis of the viscous properties of the fibre. Viscosity is the ability of gel forming that holds water and increase satiety and decreases the amount of intake food. This ability makes dietary fibre supplements considered as appetite suppressants. To date, the evidence of the effect of dietary fibre on weight is inconsistent and controversial and may be dependent on the ability of fibre to induce viscosity. Three previous meta-analyses on Konjac show inconsistency on the effect and its significance. In addition, other meta-analyses on individual viscous fibres show that some viscous fibre does not has an effect on body weight. This is the first meta-analysis that studies the effect of all these fibres together based on their viscosity.

Objective: Two systematic reviews and meta-analyses of RCTs will be conducted to evaluate the effect of viscous and non-viscous fibres on body weight, BMI, waist circumference, and body fat percentage.

Methods: To meet eligibility criteria, the study should be: randomized, controlled, include one of the selected fibres (agar, alginate, b-glucan from oat and barley, guar gum, konjac, pectin, PGX, Psyllium, and xanthan) as a supplement and one of the required outcomes (body weight, BMI, waist circumference or body fat percentage). Studies shorter than 4 weeks in duration will be excluded. Three databases (Medline, EMBASE, and Cochrane Library) were searched. After the search, a title/abstract screening was done to exclude the ineligible articles before extracting data from full eligible studies. Data were extracted using a PROFORMA. Review Manager 5.3 (RevMan) was used to carry out the analysis using generic inverse variance method (GIVM). Change from baseline and standard deviation were utilized in random effect model to get the pooled mean difference effect. Subgroup analyses were done using meta-regression in STATA to explore confounders. GRADE approach was conducted to evaluate the quality of evidence and the strength of recommendations.

Results: Databases were searched through 04/03/2016 and updated on 11/04/2017. Twenty-seven studies were eligible for analyses . The overall effect of viscous fibres on body weight was a significant reduction of -0.38 kg [95%CI: -0.3, -0.13] (P=0.003). BMI, waist circumference and body fat were also significantly reduced: -0.41 kg/m2 [95% CI: -0.61, -0.21](p = 0.0001) -0.78 cm[95%CI: -1.33, -0.24] (p = ) and -1.28 %[95% CI: -2.09, -0.46] (p = ), respectively.

Significance: This study is the first systematic review and meta-analysis that evaluated separately the effect of viscous and non-viscous fibres on weight in the general population. The analysis may help guide diet recommendations for obesity and identify the effect of fibres to direct future research this area.