Short- and long-term shifts in food purchasing behaviours and nutrition disparities in the USA during and after the COVID-19 pandemic.

The coronavirus 2019 pandemic disrupted food purchasing behaviours, triggering both short- and long-term nutritional shifts. Here, analysing 9,367,550 weekly shopping baskets from over 30,000 US households (2017-2022), combined with county-specific policies and artificial intelligence-enhanced nutrition profiling, we document distinct changes in household food baskets. During the pandemic and lockdowns, households increased spending on less processed foods, but by the post-pandemic period, spending on ultraprocessed foods rose above pre-pandemic levels. This divergence appeared strongly in processing-based measures (NOVA) but less in nutrient-based profiles (Healthy Eating Index and Food Standards Australia New Zealand), underscoring their complementary perspectives on diet quality. The spending gap between socioeconomic groups widened in 2020 but converged post-pandemic, while a new nutrition gap emerged as higher-income households increased spending on less nutritious foods. Categories such as prepared and frozen foods and carbonated beverages showed persistant effects. These findings highlight the pandemic's uneven, lasting influence on dietary behaviour and the need for policies promoting healthier, more resilient food systems.