When looking at correlation of baseline PET/SPECT findings with changes in glycemic control, two studies of RYGB/VSG surgery for obesity (with 32–38% having T2DM) found that: (i) higher whole brain BGU (during insulin stimulation) was correlated with less improvement in fasting plasma glucose (FPG) at 3 years, perhaps indicative of better insulin sensitivity at baseline with a floor effect39; and similarly (ii) higher whole brain free fatty acid (FFA) uptake was correlated with less improvement in FPG at 2 years.49 Here, INS is linked to obesity due to melanocortin 4 receptor deficiency.