A gut-microbe transplant has not yet become a metabolic treatment

The microbiome is one of the most exciting frontiers in metabolic medicine. The hypothesis is plausible: altering gut microbial communities might change insulin sensitivity. But the treatment question is simpler than the theory. Did giving fecal microbial material to patients reliably improve their glucose metabolism?

Across randomized trials, the pooled answer was inconclusive. Donor characteristics, preparation, background diets and comparators varied, and even the primary synthesis included just 120 people. That is too small and heterogeneous to turn an interesting biological mechanism into a clinical metabolic protocol.

It keeps the door open for better-designed trials while preventing an unproven intervention from appearing beside established treatments as though the evidence were comparable.

The evidence: 18 eligible randomized FMT studies in adults with metabolic disorders; primary meta-analysis drew on only six trials and 120 participants for insulin resistance measured by HOMA-IR. Between-group HOMA-IR mean difference -1.29 (95% CI -3.04 to 0.47; I² 72%): no conclusive improvement. HbA1c data were too sparse to pool across different comparators. Evidence certainty was very low for HOMA-IR and HbA1c.

resistance based on these trials.