Glycated haemoglobin and body mass index (BMI) are implicated in neurodegeneration and diabetes. Diabetes-related changes in T2* estimates and fractional amplitude of low frequency fluctuations (fALFFs) are less understood. We investigated these neuroimaging estimates within the thalamic nuclei, hippocampi, and caudate nuclei of the UK Biobank-derived pre-diabetes and diabetes adult groups. Multiple regression analyses elucidated BMI as the robust predictor of hippocampal T2* estimates in both subgroups. These metrics extracted from two pulse sequences were helpful in understanding the brain and BMI associations, which is important in the assessment of diabetes and pre-diabetes as a risk factor for neurodegenerative disorders.