LFHCC diet: ↑ Prevotella, ↓ Roseburia. Mediterranean diet: ↓ Prevotella, ↑ Roseburia & Oscillospira. Both diets: ↑ beneficial species (Parabacteroides distasonis with Med; Faecalibacterium prausnitzii with LFHCC). Microbiota shifts correlated with metabolomic changes (amino acids, peptides, sphingolipids). Overall, both diets improved gut microbial balance linked to improved insulin sensitivity and protection against T2DM development. The gene discussed is INS; the disease is type 2 diabetes mellitus.