Physiologic Response to Bariatric Surgery and the Impact of Adjunct Semaglutide in Adolescents

Observation Phase Inclusion Criteria: * Signed and dated informed consent form * Willingness to comply with all study procedures and availability for the duration of the study * Male or female biological sex, age 12 through 24 years * In the preoperative pathway for vertical sleeve gastrectomy Exclusion Criteria: * Planned Roux-en-Y gastric bypass * Hypothalamic obesity * Type 2 Diabetes * Current use of oral glucocorticoids (i.e. within 10 days of baseline visit) * Current use of insulin Intervention/Treatment Phase Inclusion Criteria: * Signed and dated informed consent form * Status post vertical sleeve gastrectomy * Male or female biological sex, age 12 through 24 years * Meeting minimum nutrition goals * Obesity: age 12-17 years: BMI ≥95th%ile for age/sex \| age 18-24 years: BMI ≥ 30kg/m\^2 * If entering the Intervention phase from the Observational phase: ≤22% BMI loss at 6-24 months postop * If entering the Intervention phase from the existing patient pool: ≤22% BMI loss at 6-24 months postop Exclusion Criteria: * Surgically correctable cause of suboptimal postoperative weight loss * Known hypersensitivity to any component of semaglutide * Personal or family history of medullary thyroid carcinoma * Personal history of multiple endocrine neoplasia type 2 * Hypothalamic Obesity * Type 2 Diabetes * History of pancreatitis * Uncontrolled hypertension * Clinically significant arrhythmia or heart disease that could be exacerbated by increased heart rate * Malignant neoplasm within the last 5 years * Untreated thyroid disorder * Tanner Stage 1 * Baseline alanine transaminase (ALT) or aspartate aminotransferase (AST) ≥ 5x upper limit of normal * Baseline Creatinine \>1.2mg/dL * Active treatment for bulimia nervosa * Active major psychiatric disorder limiting informed consent * Suicidal ideation of type 4 or 5 on Columbia-Suicide Severity Rating Scale (C-SSRS) * Intentional self-harm within the previous 1 month * Severe unmanaged depression, defined by Center for Epidemiological Studies Depression (CESD) score of 26 or greater and by clinical evaluation * Recent change to concomitant medications for hypertension, dyslipidemia, depression or anxiety (\<4 weeks prior to enrollment) * Use of oral glucocorticoids (within 10 days of baseline visit) * Use of metformin (within 3 months of baseline visit) * Use of insulin secretagogues (within 4 half-lives of the medication of baseline visit) * Current use of insulin * Use of anti-obesity medications (within 4 half-lives of the medication of baseline visit) * Current pregnancy * For females of reproductive potential: Plan to become pregnant in the next 8 months * For females of reproductive potential: Not on contraception (i.e. two forms of birth control for example oral birth control pills and condoms) for at least 1 month prior to enrollment and agreement to use these during study participation and for an additional 8 weeks after the final dose of study medication