Inclusion Criteria:
* Be 18-65 years old.
* Be actively considering bariatric surgery.
* Smoke at least 5 cigarettes daily for the past 3 months.
* Have a BMI ≥ 30.0 kg/m2.
* Not currently taking medications that interact with Naltrexone or Bupropion (e.g., opiates, benzodiazepines).
* No history of medical conditions that are contraindicated with Naltrexone or - Bupropion (e.g., seizure disorders, uncontrolled hypertension, cardiac issues including history of heart attacks, heart disease, or stroke, history of anorexia or bulimia nervosa).
* Physically well enough to participate in the intervention (e.g., able to walk independently).
* Speak/read/write in English.
* Not currently pregnant or breastfeeding or have plans to become pregnant or breastfeed during the study.
* No active suicidal or homicidal ideation.
Exclusion Criteria:
* Has an acute medical or psychiatric disorder that would make participation difficult or unsafe.
* Has suicidal or homicidal ideation that requires immediate attention.
* Has a predisposition to seizures (e.g., subject with a history or evidence of seizure disorder, febrile seizures during childhood, brain tumor, cerebrovascular disease, or significant head trauma; has a family history of idiopathic seizure disorder or is currently being treated with medications or treatment regimens that lower seizure threshold).
* Has evidence of a second or third degree heart block, atrial fibrillation, atrial flutter, prolongation of the QTc, or any other finding on the screening electrocardiogram that would preclude safe participation.
* Has stage 2 hypertension (blood pressure greater than 160/100 or heart rate over 100 beats/minute).
* Has elevated bilirubin test or any other liver function test value \> 5 times the upper limit of normal laboratory criteria.
* Has a platelet count \< 100x10 3/uL.
* Has a history of anorexia nervosa or history of bulimia nervosa.
* Is currently taking a medication that is contraindicated to Naltrexone or Bupropion (e.g., MAOIs, opiates).
* Has a history of allergy or sensitivity to Naltrexone or Bupropion.
* Has a co-existing psychiatric condition that requires hospitalization or more intensive treatment (such as bipolar mood disorders, psychotic illnesses, or severe depression).
* Has a history of congenital heart disease, cardiovascular disease, cardiac arrhythmias requiring medication, or a history of cerebrovascular pathology including stroke.
* Has current uncontrolled Type I or Type 2 diabetes mellitus.
* Has a history of severe renal, hepatic, neurological, chronic pulmonary, or gallbladder disease, or any other unstable medical disorder, including cancer.
* Has angle closure glaucoma.
* Has taken an investigational drug in another study within 30 days of study consent.
* Has been prescribed and taken Naltrexone or Bupropion within 30 days of study consent.
* Is concurrently enrolled in formal behavioral or pharmacological Substance Use Disorder treatment.
* Is receiving ongoing treatment with tricyclic antidepressants, xanthines, systemic corticosteroids, nelfinavir, efavirenz, chlorpromazine, MAOIs, central nervous stimulants, or any medication that could interact adversely with the study medications.
* Has a current pattern of alcohol, benzodiazepine, or other sedative hypnotic use which would preclude safe participation in the study.
* Requires treatment with opioid-containing medications during the study period.
* Has a surgery planned other than bariatric surgery.
* Is currently in jail, prison, or any inpatient overnight facility as required by a court of law or have pending legal action or other legal situation that could prevent participation.
* Is currently pregnant, breastfeeding, or plans to become pregnant during the study, or is not using a reliable form of birth control.
