SMART Use of Medication for the Treatment of Adolescent Severe Obesity

Inclusion Criteria: * Provision of signed and dated informed assent form; * Provision of signed and dated informed parental consent form from at least 1 legal parent/guardian; * Stated willingness to comply with all study procedures and availability for the duration of the study; * BMI \>/= 1.2 times the 95th percentile or BMI \>/= 35 Kg/m2, whichever is lower; * Tanner stage \>/= 2; * Male or female, aged 12-17 at time of consenting; * For females of reproductive potential: when sexually active, agreement to use highly effective contraception (oral contraceptive pill, intra-uterine device (IUD), or implant) during study participation; * For males of reproductive potential: use of condoms or other methods to ensure effective contraception with partner. Exclusion Criteria: * Contraindications to phentermine or topiramate use according to package inserts, including: history of glaucoma; current or recent (\< 14 days) use of monoamine oxidase inhibitor; known hypersensitivity to sympathomimetic amines; current pregnancy, plans to become pregnant, or if sexually active refusal to use 2 forms of birth control; history of cardiac disease including coronary artery disease; clinically significant cardiac arrhythmias; heart failure or uncontrolled hypertension; * Diabetes (type 1 or 2); * Presence of cardiac pacemaker; * Current or recent (\<6 months prior to enrollment) use of weight loss medication(s); * Current use of weight-altering medication(s) (e.g., atypical antipsychotic, …