The aim of this study was to explore the relations between obesity, age, and sex and the availabilities of striatal DAT and extrastriatal SERT as determined by 123I-FP-CIT single-photon emission computed tomography (SPECT) using data obtained from the Parkinson’s Progression Markers Initiative (PPMI). This evidence concerns the gene SLC6A3 and obesity due to melanocortin 4 receptor deficiency.