The effects of probiotics plus dietary fiber on antipsychotic-induced weight gain: a randomized clinical trial

Double-blind, randomized clinical trial conducted in China in adults with schizophrenia or bipolar disorder who were taking stable atypical antipsychotics and had antipsychotic-associated weight gain greater than 10%. Participants were allocated 1:1:1:1 to probiotics plus dietary fiber, probiotics alone, dietary fiber alone, or placebo and followed for 12 weeks.

Adults received oral probiotics, dietary fiber, or both for 12 weeks. The probiotic regimen was Bifico at 1680 mg/day, given as eight capsules daily; the fiber regimen was 60 g/day, given as two oral doses per day. The combination arm received both active products, while the single-active arms received a matching placebo for the other component.

The combination of probiotics plus dietary fiber produced the clearest benefit, significantly reducing weight and BMI and lowering total cholesterol versus probiotics alone, dietary fiber alone, or placebo. It also helped prevent deterioration in insulin resistance and other metabolic measures, while probiotics alone or dietary fiber alone helped prevent further weight gain. The intervention was considered safe, and constipation was more frequent in placebo after excluding constipation from the adverse-event comparison. Increased gut microbiota richness with the combined treatment was associated with favorable weight outcomes.

The active arms were relatively small, with 32 participants in the combination group and 29 in each single-intervention group, and follow-up lasted only 12 weeks. The study was conducted at a single hospital in China in a young adult psychiatric population, which limits generalizability. Sex-specific data were not reported, and some outcome reporting is incomplete or difficult to interpret for individual arm comparisons.