BRD2 and obesity due to melanocortin 4 receptor deficiency: The aim of the present study was to elucidate over a broad range of BMI (normal-weight to severe obesity) whether changes in BMI are associated with changes in central 5-HT as well as NA transmission, specifically with changes in 5-HTT and NAT availability before and after 6 months of dietary intervention or RYGB surgery.