Nationally, 12.3% of households are food insecure and, despite numerous federal food assistance programs, this rate has barely changed since the U.S. started measuring domestic food insecurity in 1995. Rates of obesity and diet-related chronic disease are also dangerously high and recent introduction of grocery stores into underserved ‘food desert’ areas has yielded only moderate health improvements. The intractability of these health and social challenges may be partially due to oversimplification of the problem; healthy food access is insufficiently explained by largely static, spatial constructs. To address these issues, we need a dynamic understanding of the interplay between and spatiotemporal dimensions of food consumption, food environments, institutional food resources, and social networks. Using a mixed-methods approach, this dissertation examines associations between the monthly SNAP (food stamp) benefit distribution cycle and the diet quality, chronic disease management, and coping strategies of low-income households. By working at the policy, community and household levels, this research illustrates how food access and food insecurity are the product of a relational, ecological model. Statistical analysis using the nationally representative FoodAPS dataset revealed low diet quality for SNAP households throughout the month with small, but significant declines in healthfulness of food purchases in the final 10 days of the benefit cycle, suggesting that as benefits are depleted, households adjust their food purchasing. Complementing the national scan, primary research (including 50+ hours of interviews and participant observation) explored the experiences of 18 Philadelphia households in the end-of-month period when SNAP runs out, with particular attention to impacts on health. This in-depth fieldwork revealed frequent use among SNAP households of physically distant (non-neighborhood) food resources, difficulty affording foods necessary for chronic disease management, and reliance on social support and emotional coping strategies, particularly at the end of the SNAP cycle, to ease the stress of monthly financial volatility. Findings elucidated how, in filling the gaps of a weakened social safety net, low-income households are often required to make tradeoffs that do not favor health. This research provides compelling new contributions to investigations of urban food access, food insecurity, and the health and social welfare consequences of SNAP policy.