DRD2 and obesity due to melanocortin 4 receptor deficiency: However, in other studies, correlations between DRD2/3 receptor availability and BMI or obesity have been highly inconsistent, likely related to (i) multiple different tracers with variable characteristics, (ii) neuroanatomical localization of BP differences, (iii) severity of obesity (with some reviews suggesting inverted U‐shape relationship), (iv) potential differential effects of tonic and phasic dopamine release, and (v) variable sample sizes.58, 60, 61