Lactobacillus helveticus UA881 Improves Body Composition, Lipid Profiles, and Gut Microbiota in Overweight Adults: A Randomized Double-Blind Placebo-Controlled Trial

<b>Background:</b> Overweight and metabolic disorders are strongly associated with gut microbiota dysbiosis. Probiotics represent a safe dietary strategy to improve metabolic health, although strain-specific effects remain unclear. This study evaluated the metabolic and gut microbiota-modulating effects of <i>Lactobacillus helveticus</i> (UA881) in overweight adults. <b>Methods:</b> In a randomized, double-blind, placebo-controlled trial, 50 overweight adults (Body mass index, BMI 25-27 kg/m²) were assigned to receive UA881 (5 × 10⁹ CFU/day) or placebo for 28 days. Anthropometric parameters, body composition, serum biochemical markers, inflammatory cytokines, fecal short-chain fatty acids (SCFAs), and gut microbiota composition (16S rRNA sequencing) were assessed at baseline and after 28 days. Statistical analyses included paired <i>t</i>-tests and ANCOVA adjusted for baseline values. <b>Results:</b> After 28 days of supplementation, UA881 significantly reduced body weight, BMI, and body fat mass. The primary endpoint, serum triglycerides, was significantly decreased, and the increases in uric acid, total cholesterol, and Low density lipoprotein-cholesterol (LDL-C) observed in the placebo group were attenuated. No significant changes were observed in interleukin-6 (IL-6) or tumor necrosis factor-α (TNF-α) levels. Fecal butanoic acid showed an increasing trend, and gut microbiota alpha diversity was significantly improved. At the genus level, <i>Anaerostipes</i> and <i>Blautia</i> were enriched, while <i>Collinsella</i> was reduced. <b>Conclusions:</b> A 28-day supplementation with <i>L. helveticus</i> UA881 (5 × 10⁹ CFU/day) improved body composition and lipid-related metabolic parameters and favorably modulated gut microbiota composition in overweight adults, supporting its potential as a probiotic candidate for metabolic health.