The Effect of Microbiome Therapies on Waist Circumference, a Measure of Central Obesity, in Patients with Type 2 Diabetes: A Systematic Review and Meta-analysis of Randomized Controlled Trials

Background Microbiome therapies (probiotic, prebiotic, and synbiotics) have been proposed as adjuvants in the control of central obesity; however, their results for pa-tients with type 2 diabetes (T2D) remain inconclusive.Objective The aim of this systematic review and meta-analysis was to evaluate the effect of microbiome therapies on central obesity as measured by waist circumference (WC), and to evaluate the effect of microbiome therapies for glycemic parameters (fasting glucose [FPG], fasting insulin [FPI], hemoglobin A1c [HbA1c], and insulin resistance [HOMA1-IR]) in patients with T2D.Methods SCOPUS, Pubmed, EBSCO, and LILACS databases were searched for studies that investigated the effect of microbiome therapies on WC up to June 1, 2022. Het-erogeneity was determined using Cochran's Q test and quantified using the inconsis-tency index. The random effects model was used to calculate the pooled difference in means (DM) and 95% confidence intervals (95%CI). Egger's test and Beggs-Muzamar's test were used to assess publication bias.Results Fifteen reports were included (443 treated and 387 controls). Overall, a sig-nificant decrease in WC was found (DM =-0.97 cm; 95% confidence interval [95%CI] =-1.74 to-0.20; P = 0.014); however, when stratified by type of microbiome therapy, only probiotics significantly decreased WC (DM =-0.62 cm; 95%CI =-1.00 to-0.24; P = 0.002). No effect was observed for prebiotics and synbiotics. With respect to gly-cemic parameters, HbA1c, FPG, and HOMA1-IR significantly decrease with microbiome therapies (P < 0.001). When stratified by the type of therapy, for probiotic treatments, HbA1c, FPG, and HOMA1-IR scores decrease (P < 0.001). For prebiotic treatments, HbA1c and FPG (P < 0.001) levels decrease, whereas FPI increased (P = 0.012). Synbiotic treatments were only associated with an increase in FPI (P = 0.031). Conclusion Findings indicate that using probiotics alone improved WC in patients with T2D. Both probiotics and prebiotics decreased HbA1c and FPG; however, prebiotics and synbiotics resulted in an increase in FPI. The formulation of the therapy (single vs multi) had no difference on the effect. J Acad Nutr Diet. 2023;123(6):933-952.