Lastly, the complex interplay between obesity in chronic pain states as well as FMS, leptin and the HPA-axis has been investigated with growing interest by the scientific community [22], whereas obesity is a common comorbidity in FMS and has also been shown to increase symptom severity [23–26], Leptin levels in relation to painful conditions have been found to be either unaltered [27], elevated [28–31] or reduced [32] compared with controls. Here, LEP is linked to obesity due to melanocortin 4 receptor deficiency.