ESG in Obese Adolescents

The primary goal of this pilot study is to learn if the use of the Apollo Endosurgery ESG System is a safe, well tolerated intervention for weight loss in adolescents with obesity. Secondary outcomes will evaluate the effectiveness of Endoscopic Sleeve Gastroplasty (ESG) in long-term reduction of weight, improvements in obesity-related co-morbidities and improvements in quality of life. Participants will: * Have their stomach volume reduced with the ESG procedure (study intervention), rather than with a bariatric surgery, under general anesthesia * Undergo pregnancy testing (female participants only) * Be admitted overnight to the hospital for recovery and monitoring following the ESG procedure * Have a physical examination performed at study follow-up visits * Participate in surveys about any side effects from the procedure and about quality of life * Follow-up with the study team. * Participants will still be seen in the multidisciplinary Bariatrics Clinic team consisting of an obesity medicine doctor, registered dietician, physical activity specialist, and psychologist as part of normal standard of care.