Patients who have not taken part in any previous setmelanotide clinical trial must fulfill all of the following study's eligibility criteria:  Inclusion Criteria:  Clinical diagnosis of BBS Males and females aged ≥6 years Obesity (≥30 kg/m2) for patients ≥18 years old or weight >97th percentile for age and sex on growth chart assessment for patients aged 6 to 17 years Female participants of child-bearing potential must be confirmed as non-pregnant Patients with significant neuropsychiatric disorders such as depression should be carefully evaluated regarding the benefit/risk ratio for the use of setmelanotide Patients unable to enroll in another clinical trial with setmelanotide as determined by the treating physician  Exclusion Criteria:  Moderate to severe renal dysfunction defined as a glomerular filtration rate (GFR) <60 mL/min/1.73m2 History or close family history (parents or siblings) of skin cancer (excluding non-invasive basal or squamous cell lesion) melanoma, or patient history of ocular cutaneous albinism Inability to comply with a daily injection regimen  Patients who have taken part in any previous setmelanotide clinical trial, have met all of the study's eligibility criteria, and have shown meaningful clinical benefit, defined as at least a 5% reduction in body weight for patients aged ≥18 years or a 5% reduction in BMI in patients aged <18 years from baseline through the end of the preceding study, will be eligible.