PROJECT SUMMARY/ABSTRACT Obesity is a public health epidemic in the United States and contributes to many other adverse cardiometabolic outcomes, such as heart disease. Unhealthy diet is a major risk factor in the etiology of obesity, and low-income individuals and women with young children experience disproportionate rates of both inadequate nutrition and excess weight. Interventions to improve dietary patterns have had mixed success, likely because they have targeted the individual, and largely ignored the complex ecological systems that influence eating. Precision nutrition science initiatives are encouraging more understanding of the complex systems that influence diet. Two systems that may be especially impactful for low-income individuals are social networks and neighborhood food environments, as these individuals tend to be embedded in social networks with less resources and support, and they are more likely to live in neighborhoods with reduced access to healthy food. Many features of these two systems have been linked with unhealthy dietary patterns, such as living in a food desert and having a social network that is mostly overweight. However, previous social network studies have not examined other key features and have had methodological limitations such as lack of population-level data, and sparse information of few network members. Social networks and neighborhood food environments have also been studied in isolation, meaning the synergistic impact of these systems on the diets of low-income populations is not understood. The goal of this study is to examine, simultaneously, the main and interaction effects of (1) living in a food desert and (2) personal social network characteristics on the dietary patterns and body mass index (BMI) of low-income adults and mothers. This project will leverage data from two unique datasets that each have notable strengths: (1) The Understanding America Study, with longitudinal data from 550 low-income individuals who are representative of Los Angeles (LA) County, CA, allowing for the identification of population-level effects and (2) The NICHD-funded Healthy Habits clinical trial, with both qualitative and quantitative longitudinal data from 70 low-income mothers in Antelope Valley, LA County, CA, allowing for an in-depth mixed methods exploration. The findings from this study will give a fully-formed understanding of the independent and synergistic impacts of social networks and neighborhood food environments on dietary patterns and BMI, and contribute to interventions that are tailored to multiple levels of influence. The award of this fellowship will allow Ms. Miller to pursue advanced training opportunities in Social Network Analysis, Geographic Information Science, and longitudinal and population-level data analysis, in pursuit of her goal of becoming an independent academic research scientist.