ABSTRACT Food insecurity affected 11% of all US households in 2020, and youth and young adults with type 1 diabetes (T1D) or type 2 diabetes (T2D) experience even higher rates of food insecurity, 18% and 31%, respectively. Moreover, 56% of youth and young adults with T1D and 46% of those with T2D do not achieve optimal glycemic control, with young people from underrepresented racial/ethnic groups experiencing much higher rates of poor glycemic control. We propose a continuation of the NIDDK-funded SEARCH Food Security Cohort Study (SFS 1), which collected data on >1,000 youth and young adults with diabetes and documented the role food insecurity plays in influencing glycemic control and related outcomes. SFS 1 data indicate that compared to those who are food secure: (a) young people with T1D and food insecurity have higher HbA1c (+0.34%, p=0.04) and (b) those with T2D and food insecurity have higher odds of diabetic ketoacidosis (3.1, p=0.02) in fully adjusted models. However, food insecurity varies day-to-day and ranges from intermittent to persistent, and SFS 1 did not capture the day-to-day variation, which is needed for intervention planning. Thus, we propose a research strategy of high scientific rigor that will integrate longitudinal quantitative and qualitative methods, including ecological momentary assessment (EMA) and continuous glucose monitoring (CGM), in an intensive, mixed methods study. This proposal (SFS 2) greatly expands our work in SFS 1 toward identifying the temporal causal cascades and actionable and acceptable interventions for eliminating food insecurity. To achieve these goals, we aim to (1) leverage the ongoing SFS 1 study to enroll a cohort of 360 youth and young adults with diabetes (260 T1D, 100 T2D), 72% with a history of food insecurity, for a repeated-measures, longitudinal mixed methods study over 9 months; (2) evaluate differences in real-time glycemic control between participants with varying levels of food insecurity, assessed by average daily time in range (TIR) via CGM over two 14-day time periods spaced 9 months apart; (3) evaluate the within-participant impact of food insecurity on TIR and intermediate paths using EMA methods, including dynamic structural equation models; (4) use longitudinal, qualitative methods to concurrently and deeply characterize the context of participants’ food insecurity experience and coping process, by conducting a concurrent events study of 30 individuals with T1D and 15 with T2D with a history of food insecurity through in-depth, one-on-one, repeated semi-structured interviews over 9 months. This study will integrate intensive data collection of the primary outcome (TIR by CGM) and the primary exposure (daily food insecurity), as well as measures of physical activity, diet, and mood. These quantitative data will be complemented by longitudinal qualitative interviews, which will allow us to triangulate the quantitative data with participants’ lived experiences. The findings wil...