Vyvanse in Children Aged 6 to 12 Years

This study will randomize children who have difficulty maintaining a healthy weight to one of two treatment groups: lifestyle therapy plus lisdexamfetamine or lifestyle therapy plus placebo.

This pilot study will enroll up to 40 children aged 6 to 12 years who have severe obesity. Individuals will be randomized to receive lifestyle therapy plus lisdexamfetamine or lifestyle therapy plus placebo. Participants will receive therapy for 24 weeks.

Eligibility Criteria:
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 at the screening OR baseline/randomization visits
* Tachycardia defined heart rate (HR) \>/= 120 bpm at the screening OR baseline/randomization visits
* Current or recent (\< 3 months) use of psychostimulant or sympathomimetic amine
* History of chemical dependency
* Diabetes mellitus (type 1 or 2)
* Current or recent (\< 3 months) use of anti-obesity medication(s)
* Previous bariatric surgery
* Recent initiation or change in dose (\< 3 months prior) of anti-hypertensive or lipid medication(s)
* Thyroid stimulating hormone (TSH) \> 1.5x upper limit of normal (ULN)
* Aspartate transaminase (AST) or alanine transaminase (ALT) \> 3x ULN
* Fasting glucose \>/= 126 mg/dL
* History of mania, schizophrenia, bipolar disorder, or psychosis
* Unstable depression or anxiety that has required hospitalization in the past 12 months
* Any history of suicide attempt
* Columbia Suicide Severity Rating Scale (C-SSRS) with a score of Moderate or Hiogh at the screening or baseline/randomization visits
* Children's Depressive Inventory 2 (CDE-2_ score \>/= 70 (based on parent or child report) at the screening or baseline/randomization visits
* Concomitant use of tricyclic antidepressants, selective serotonin re-uptake inhibitors (SSRIs), serotonin and norepinephrine re-uptake inhibitors (SNRIs), lithium, fentanyl, tramadol, triptans, tryptophan, buspirone and St. John's wort at any time during the study
* Refusal to use adequate contraception (double barrier method or stable hormonal contraception plus single barrier method, tubal ligation, or abstinence) in girls of childbearing potential