INS and type 2 diabetes mellitus: A high-fiber diet has been shown to improve glucose homeostasis in patients with T2DM. A high-fiber diet significantly decreased the serum levels of HbA1c and FBG. Mutating the gut microbiota by adding a high-fiber diet resulted in lower levels of inflammatory cytokines and increased tight junction integrity. High fiber diets resulted in increased levels of Firmicutes and Bacteroidota levels, resulting in better insulin control.