DRD2 and obesity due to melanocortin 4 receptor deficiency: While most other previous studies did not investigate both continuous and weight group specific effects in fMRI, a non-linear relationship between body weight and other measures of neural reward has been found and discussed previously, especially in the context of dopamine receptor binding potential: Morbid obesity has been linked to less striatal dopamine (D2) receptor availability when compared to participants with a lean BMI and a negative association between D2 and BMI was only significant in the group with obesity in another investigation (Wang et al., 2001).