Vyvanse in Children Aged 6 to 12 Years

Inclusion Criteria: * Children ages 6 to \<12 years at study entry * Severe obesity defined as BMI \>/= 1.2 times the 95th percentile at the screening visit * Prior failed attempt of lifestyle therapy per parent/guardian report * Written informed consent of parent/legal guardian and written assent of participant Exclusion Criteria: * Contraindications to lisdexamfetamine, including current or recent (\< 14 days) use of monoamine oxidase inhibitor and known hypersensitivity to amphetamine products * Family history of sudden death or ventricular arrhythmia in any first or second degree relative with any of the following: sudden or unexplained death including sudden infant death syndrome, cardiomyopathy, heart transplant, familial arrhythmia (such as Wolff-Parkinson-White syndrome, long QT interval, or implantable defibrillator). * Any history of fainting or seizure from exercise, startle, or fright * Clinically significant congenital or structural heart disease or arrhythmia * BMI \<1.2 times the 95th percentile at the baseline/randomization visits * Hypertension defined as systolic blood pressure (SBP) and/or diastolic blood pressure (DBP) \>/= 95th percentile (on 3 separate occasions) at the screening OR baseline/randomization visits * Tachycardia defined heart rate (HR) \>/= 120 bpm (on 3 separate occasions) at the screening OR baseline/randomization visits * Current or recent (\< 3 months) use of psychostimulant or sympathomimetic amine * History of chemical dependency *…