Therefore, in the current study, we measured plasma GFAP levels in T2D patients following the O-BN diet for 3 months and analyzed possible correlations with psychological well-being and the neurodegeneration marker neurofilament light polypeptide (NfL) in addition to peripheral metabolic (e.g., glucose, insulin) and inflammation (e.g., cytokines) markers, as well as markers for gut barrier leakage. Here, NEFL is linked to type 2 diabetes mellitus.