This study will test the effectiveness of lisdexamfetamine medication as a treatment for loss-of-control eating and weight following bariatric surgery. This is a controlled test of whether, amongst non-responders to acute treatments, lisdexamfetamine medication results in superior outcomes compared with placebo.

Inclusion Criteria:

• Be in the age range ≥18 years of age and <65 years of age.
• Have had laparoscopic Roux-en-Y gastric bypass or sleeve gastrectomy
• Approximately ten months post-surgery
• Experienced regular loss of control eating about six months after bariatric surgery, and were considered treatment non-responders to a four-month treatment trial of medication and/or BWL
• Be an otherwise healthy subject without uncontrolled medical problems, as determined by the study physician and medical co-investigators (physical examination, laboratory studies).
• Read, comprehend, and write English at a sufficient level to complete study-related materials.
• Provide a signed and dated written informed consent prior to study participation.
• Be available for participation in the study for up to 15 months (3-month treatment plus 12-month follow up).

Exclusion Criteria:

• 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 a history of anorexia nervosa or history of bulimia nervosa.
• Is currently using other medications for weight loss.
• Has a co-existing psychiatric condition that requires hospitalization or more intensive treatment (such as bipolar mood disorders, psychotic illnesses, or severe depression)
• Has untreated hypertension with a seated systolic blood pressure > 160 mmHg, diastolic blood pressure > 100 mmHg, or heart rate > 100 beats/minute.
• Has a history of congenital heart disease, cardiovascular disease, cardiac arrhythmias requiring medication, or a history of cerebrovascular pathology including stroke.
• Has current uncontrolled hypertension.
• Has current uncontrolled Type I or Type II diabetes mellitus.
• Has untreated hypothyroidism with a TSH > 1.5 times the upper limit of normal for the test laboratory with repeat value that also exceeds this limit.
• Has gallbladder disease.
• Has a history of severe renal, hepatic, neurological, chronic pulmonary disease, or any other unstable medical disorder.
• Is currently in active treatment for eating or weight loss.
• Is currently participating in another clinical study in which the subject is or will be exposed to an investigational or a non-investigational drug or device.
• Is breast-feeding or is pregnant or is not using a reliable form of birth control.
• Reports active suicidal or homicidal ideation.
• Previous history of problems with LDX or other stimulants.
• Has a history of allergy or sensitivity to LDX or other stimulant medications.
• Current medication contraindicated with study medication.
• Any current psychostimulant use or any medication for ADHD.
• History or current alcohol or substance use disorder (smoking will not be exclusionary)
• Is currently taking MAOI medication, SSRI medication, or strong inhibitors of CYP2D6