Metabolic hormones stabilize brain reward and motivational circuits, whereas excessive opioid consumption counteracts this effect and may impair metabolic function. Here we addressed the role of metabolic processes in the course of the agonist medication-assisted treatment for opioid use disorder (OUD) with buprenorphine or methadone. Plasma lipids, hemoglobin A1C, body composition, the oral glucose tolerance test (oGtt) and the Sweet taste test (Stt) were measured in buprenorphine-(n = 26) or methadone (n = 32)-treated subjects with OUD. On the whole, the subjects in both groups were overweight or obese and insulin resistant; they displayed similar oGtt and Stt performance. As compared to methadone-treated subjects, those on buprenorphine had significantly lower rates of metabolic syndrome (MetS) along with better values of the high-density lipoproteins (HDL). Subjects with-vs. without MetS tended to have greater addiction severity. correlative analyses revealed that more buprenorphine exposure duration was associated with better HDL and opioid craving values. in contrast, more methadone exposure duration was associated with worse triglycerides-, HDL-, blood pressure-, fasting glucose-and hemoglobin A1C values. Buprenorphine appears to produce beneficial HDL-and craving effects and, contrary to methadone, its role in the metabolic derangements is not obvious. our data call for further research aimed at understanding the distinctive features of buprenorphine metabolic effects vis-à-vis those of methadone and their potential role in these drugs' unique therapeutic profiles. Opioid use disorder (OUD) is an ominous public health problem afflicting about 16 million people worldwide 1. In the US, OUD constitutes the seventh cause for disability-adjusted life-years 2-4 ; including opioids' propensity 5 for the excessive body weight gain (BWG) and its medical sequelae in the form of the 'Metabolic Syndrome' (MetS) 5-7 , that is to say, a cluster of interrelated cardiometabolic risk factors comprised of insulin resistance, impaired glucose tolerance, dyslipidemia, abdominal adiposity and hypertension 8-10. Consequently, even though medication-assisted treatment (MAT) via opioid agonist replacement with long-acting opioids namely, buprenorphine and methadone, usually yields positive clinical outcomes in terms of overdose mortality, infectious diseases, crime, and societal ties 11-14 concerns have been raised about further worsening of the metabolic status 5. There are several lines of evidence that link OUD to metabolic derangements. With regard to genetic antecedents, the TCF7L2 gene codes a transcription factor implicated 15,16 in non-insulin-dependent