The countries of Central and Eastern Europe (CEE) underwent profound socioeconomic transformation following the collapse of communist regimes in the late 1980s and early 1990s. These transitions were accompanied by rapid liberalization of food markets, the entry of multinational food corporations, and fundamental restructuring of food environments. Concurrently, the region has experienced a marked rise in overweight and obesity prevalence, with several CEE countries now ranking among the highest in Europe. Ultra-processed foods (UPFs), as defined by the NOVA classification system, are industrially manufactured formulations that are energy-dense, nutrient-poor, and increasingly prevalent in post-transition food environments. The specific context of CEE countries remains underrepresented in English-language literature. This narrative review synthesizes available evidence on food environment transformation in CEE since 1990, documents trends in UPF availability and consumption, examines biological mechanisms linking UPF intake to obesity, and evaluates the current policy landscape. Evidence suggests that post-communist market liberalization created conditions favorable to UPF market expansion, contributing to dietary shifts that may help explain rising obesity rates. Public health responses in CEE have lagged behind those in both Western Europe and Latin America, creating a critical gap that requires urgent policy attention.