Project Summary While the prevalence rates of pediatric obesity have plateaued in recent years, a staggering 35% of school age children remain classified as overweight or obese. Children from ethnic minority groups are at an even greater risk, with nearly 40% of Latino children so-classified by age 6. The physical and mental health risks and societal costs associated with pediatric obesity are well established. It is thus crucial for research efforts to focus on understanding early behavioral phenotypes that can explain individual variability in children’s regulation of energy balance and subsequent weight trajectory. Researchers have documented self-regulation (SR) and poor executive function (EF) as important mechanisms for understanding the development of pediatric obesity, as well as its shared co-morbidities with other mental health disorders (e.g., Attention-Deficit/Hyperactivity Disorder [ADHD]). Poor executive function (EF), emotion regulation and reactivity (ER), and reward sensitivity (RS) have variously emerged as critical underlying processes in terms of contributing to overeating and food preferences. However, there is a lack of 1) integration of these SR processes when examining weight outcomes, 2) longitudinal studies, which are needed to disentangle whether potential SR deficits are risk factors for the development of obesity or a consequence of it, 3) comprehensive measurement of these SR processes in terms of integrating behavioral measures, neuropsychological, and neurobiological markers, 4) studies examining the predictive association of SR processes as they relate to observed obesogenic mechanisms (e.g., SR of energy intake, healthy- habits) and 5) how environmental factors (e.g., parenting, home environment) can contribute to and moderate the link between SR phenotypes and weight outcomes. Consistent with PAR-18-105, we leverage the ongoing data collection as part of award R01MH112588 (PIs Graziano and Dick), which is measuring young children’s (ages 4 to 6) SR processes (EF, ER, and RS) at a behavioral, neuropsychological, and neurobiological level using MRI. The proposed ancillary study (n = 288) examines how SR phenotypes predict obesogenic mechanisms and subsequent obesity-related trajectories. The proposed sample offers a unique opportunity to examine health outcomes within a typically understudied, yet high-risk population for obesity (i.e., Hispanic/Latino) along with inclusion of a clinical group (i.e., children with ADHD).