While the low body weight of Tph2−/− contrasts previous findings and conclusions, observation of obesity in Tph2+/− (exhibiting reduced brain 5-HT) as reflected by excess abdominal and pericardial fat storage, particularly in Tph2+/− females beyond 24 weeks, concurs. Here, TPH2 is linked to obesity due to melanocortin 4 receptor deficiency.