Exenatide in Extreme Pediatric Obesity

26 (approximately 13 per site) extremely obese (Body mass index \[BMI\] \> or = 1.2 times the 95th percentile or BMI \> or = 35 kg/m2) adolescents (age 12-19 years old) will be enrolled in a six-month study consisting of a three-month, randomized, double-blind (participants and investigators), placebo-controlled pilot clinical trial phase followed by a three-month open-label extension during which all participants will receive exenatide. For the initial three-month phase, participants will be equally (by site) and randomly assigned to one of two groups: 1) exenatide plus lifestyle modification, or 2) placebo plus lifestyle modification. Following baseline testing, subjects will be randomly assigned to study group. Participants will return at one-month for titration and assessment of safety (blood draw and adverse event assessment) and injection/lifestyle modification compliance and at three-months for reassessment of baseline variables and injection/lifestyle modification compliance and allocation to study drug for the three-month open-label extension. Participants will return at four-months for assessment of safety (blood draw and adverse event assessment) and injection/lifestyle modification compliance and at six-months for reassessment of baseline variables and injection/lifestyle modification compliance. All subjects, regardless of group assignment, will participate in the clinical lifestyle modification program offered through either the University of Minnesota or Children's Hospitals and Clinics weight management programs. Participants and their families receive regular (approximately bi-monthly) face-to-face and/or phone behavioral-, dietary-, and physical activity-counseling from a multi-disciplinary team of health care professionals including physicians, dieticians, registered nurses, psychologists, and exercise physiologists. Screening will include review of medical records for previous clinical and laboratory data. The following measures will be collected at baseline, 3 months, and 6 months. Subject will be asked to fast for a minimum of 12 hours.