Phentermine-Topiramate for Obese Patients with Ulcerative Colitis

Inclusion Criteria: * adults aged 18-80y * BMI ≥30kg/m\^2 * established diagnosis of UC based on clinical and endoscopy evidence corroborated by histopathology report * active UC (Mayo Clinic score \[MCS\], 6-12; or active disease based on rectal bleeding score \[RBS\]=2 or 3 and stool frequency score=2 or 3) or dependent on corticosteroids (unable to taper below 10mg prednisone equivalent, or flaring within 2 months of stopping prednisone) * starting a new biologic agent (TNFα antagonists, vedolizumab, ustekinumab) or flaring despite stable maintenance dose of biologic agent * stable weight (\<5kg weight change) for preceding 4 weeks prior to screening and randomization * able to speak or understand English and provide written informed consent. Exclusion Criteria: * pregnant or lactating women * prisoners * current or history of toxic megacolon, abdominal abscess, symptomatic intestinal or colonic stricture, history of colectomy or diverting stoma, short bowel syndrome, active tuberculosis or other bacterial infections, cancer * any unstable or uncontrolled cardiovascular, pulmonary, hepatic, renal, gastrointestinal, genitourinary, hematological, coagulation, immunological, endocrine/metabolic, or other medical disorder that, in the opinion of the investigator, would confound the study results or compromise patient safety * clinically meaningful laboratory abnormalities, including significant anemia (Hb\<8g/dl), leukopenia (\<3x10\^9/L), thrombocytopenia (\<100K) or thrombocytosis (\>600K), ALT/AST \>3x upper limit of normal, creatinine \>2x upper limit of normal * blood pressure \>140/95mmHg (ok to include if BP controlled on anti-hypertensives), fasting blood glucose \>240mg/dl or HbA1c \>9%, fasting triglycerides \>400mg/dl at randomization, type 1 diabetes, coronary artery disease, stroke, or other symptomatic peripheral arterial disease * history of nephrolithiasis (H/O kidney stone \>1 time, and kidney stone within 1y prior to start of study), hyperthyroidism, seizure disorder * recurrent major depression, presence or history of suicidal behavior or ideation with intent to act, current substantial depressive symptoms (patient health questionnaire-9, ≥10), use of antidepressant medication that has not been stable for the prior 3 months (bupropion-treated patients will be excluded) * history of (or treatment for) glaucoma or increased intraocular pressure * prior bariatric surgery; \>5 kg weight fluctuation in preceding 4 weeks, use of very-low-calorie diet, or participation in a formal weight loss program in the 3 months prior to the study * smoking cessation within previous 3 months or plans to quit during the study period * history of eating disorder or drug/alcohol abuse within the preceding 1 year concomitant use of other sympathomimetic medications, for example for ADHD * known allergy to study medication