Faecal microbiota transplantation did not significantly reduce HOMA-IR in patients with metabolic disordersFecal Microbiota Transplantation Shows Limited Benefit for Insulin Resistance

BackgroundFaecal microbiota transplantation (FMT) may improve glucose metabolism, but findings from randomised trials and previous meta-analyses are inconsistent. We evaluated the effects of FMT on glycaemic outcomes in adults with type 2 diabetes, prediabetes, insulin resistance or related metabolic disorders.MethodsWe searched PubMed and Scopus for English-language randomised controlled trials published from January 2000 to May 2026. The primary outcome was change from baseline in HOMA-IR. Secondary outcomes included HbA1c, fasting glucose and clamp-derived peripheral insulin sensitivity. Random-effects meta-analyses used Paule–Mandel estimation with Hartung–Knapp–Sidik–Jonkman confidence intervals. Sensitivity analyses evaluated comparator type, data reconstruction, the assumed baseline–follow-up correlation and individual-study influence. Risk of bias was assessed using RoB 2.ResultsThe searches identified 887 records, and 18 studies met the eligibility criteria. Six trials involving 120 participants included to the primary analysis. FMT did not significantly reduce HOMA-IR compared with control (MD, −1.29; 95% CI [−3.04, 0.47]; I2 = 72%). The sensitivity analysis combining HOMA-IR and HOMA2-IR also produced a non-significant result (MD, −1.11; 95% CI [−2.50, 0.29]). HbA1c data were sparse and were not pooled across comparator types. Clamp-derived findings suggested a possible donor-phenotype effect but remained inconclusive. The certainty of evidence was very low for HOMA-IR and HbA1c and low for peripheral insulin sensitivity.ConclusionsFMT did not demonstrate a clear benefit for glycaemic outcomes. The estimates were imprecise, heterogeneous and influenced by comparator design. Larger trials with standardised outcomes and predefined donor phenotypes are required.