Food- vs. supplement-based very-low-energy diets and gut microbiome composition in women with high body mass index: A randomized controlled trial.

In a single-blind, two-arm, randomized controlled-feeding trial (May 2021-February 2022), 47 women (30-65 years, BMI 30-45 kg/m2) are randomized to either a food-based or a supplement-based very-low-energy diet (VLED: 800-900 kcal/d) for 3 weeks. The food-based VLED comprises pre-packaged meals (∼93% whole-food ingredients), while the supplement-based VLED comprises shakes, soups, bars, and desserts (∼70% industrial ingredients). The primary outcome is species-level alpha diversity (Shannon index). Secondary outcomes include species richness, beta diversity, taxonomic composition, functional potential, anthropometrics, serum biomarkers, mental health, sleep, and gastrointestinal symptoms. Modified intention-to-treat (mITT) analyses (n = 45) assess diet group × time interactions as beta coefficients (β) with 95% confidence intervals (CIs). A between-group differential change is observed for the Shannon index, with a greater increase in the food-based group (mITT β: 0.37, 95% CI: 0.15-0.60). The food-based group also shows greater species richness, smaller beta diversity shifts, and compositional changes preserving fiber-degrading, health-associated taxa.