Abstract An emerging body of evidence suggests children gain more weight during the 3-month summer vacation than they do during the entire 9-month school year. This accelerated weight gain during summer is disproportionately higher among children from low-income families compared to their higher-income peers. Studies of children who respond positively to summer (i.e., maintain or lose weight, increase activity/sleep, reduce screen time, improve diet) can provide insight into what enables some children to overcome barriers linked to accelerated weight-gain during summer, while others do not. To address this important question, I will employ the Positive Deviance framework and apply it to childhood obesity.The Positive Deviance (PD) framework proposes that within any population, there are those who manage to engage in healthy behaviors despite experiencing similar obstacles as those who do not. The PD framework has been used to solve complex public health issues such as malnutrition, infant mortality, and infectious diseases. Positive deviance identifies individuals quantitatively and utilizes quantitative analyses and qualitative interviewing techniques to discover what innovative strategies PDs use to overcome barriers to improving their health. The objectives of this F31 Diversity Fellowship application are to identify neighborhood, home, parent, and child-level factors, using the PD framework, that are associated with healthful changes in children’s obesogenic behaviors – Moderate-Vigorous Physical Activity, Sedentary time, Sleep, and Diet - and changes in weight during summer. To accomplish these objectives, this study will leverage data from a large observational cohort (R01- DK116665, PI Beets) comparing changes in weight & obesogenic behaviors of low and high-income elementary-age children during school and summer vacation. The proposed study will purposively sample, from the existing cohort of 673 children, individuals who display favorable outcomes during summer. I will define PDs as children who exhibit favorable changes in BMI Z-score (zBMI) from school to summer. Quantitative analyses will assess associations between neighborhood, home, parent, and child-level factors with changes in zBMI and health behaviors. Qualitative methods, grounded in the PD Framework, will identify strategies utilized by the parents of PD children that are not present among parents of children who exhibit the least healthy changes in weight and obesogenic behaviors. The results of this F31 will be used to support the development of novel interventions to be tested in a F32 award application upon completion of the doctoral program.