Effect of Chitosan Supplementation and Lifestyle Changes on Health and Gut Microbiota in Icelandic Females With Obesity.

Evaluate the effect of chitosan supplementation with structured lifestyle changes on health factors and gut microbiota in females with obesity following an interdisciplinary rehabilitation program. In this randomized, double-blind, placebo-controlled trial (NCT04551365), 33 Icelandic females with obesity (BMI 30.0-54.1 kg/m2) received 3 g/day of LipoSan Ultra chitosan (TRG, n = 18) or placebo (PLG, n = 15) for 12 weeks, alongside structured lifestyle changes. Clinical, anthropometric (DXA), and functional data were collected at baseline (T1) and post-intervention (T3). Gut microbiota (16S rRNA) data were collected at T1, T2 (2 weeks), T3, and T4 (2 weeks post-intervention). Structured lifestyle interventions increased lean mass, grip strength, endurance, and self-rated health, while reducing body fat mass and mean arterial pressure across BMI groups. Participants with BMI ≥ 40 kg/m2 showed decreased microbiota diversity over time. Chitosan supplementation was linked to a reduction in the Firmicutes/Bacteroidota ratio, although no differentially abundant taxa were identified (ANCOM-BC2). Structured lifestyle interventions improved body composition and physical function, independently of weight loss. Chitosan supplementation modulated gut microbiota composition. Interpretation of subgroup and gut microbiota findings is constrained by the study size. Future studies should investigate long-term effects and stratify outcomes by BMI to better evaluate chitosan's therapeutic potential.