We measured ATX levels in 69 men and women (mean age: 41 ± 11 years, body mass index: 49.8 ± 7.1 kg/m2), before and after biliopancreatic diversion with duodenal switch surgery (BPD‐DS) as well as in a control group (patients with severe obesity without surgery; n = 34). Here, ENPP2 is linked to obesity due to melanocortin 4 receptor deficiency.