Food insecurity and undernourishment remain persistent challenges in developing countries, particularly under conditions of economic volatility, income inequality, food price instability, and increasing pressure on food systems. This study examines the macroeconomic and structural determinants of undernourishment in developing countries within the broader framework of sustainable food systems. The analysis focuses on GDP per capita, agricultural value added, and inflation, while urbanization and trade openness are included as control variables. An unbalanced panel dataset covering 72 developing countries over the period 2010–2023 is employed. Fixed effects and random effects panel models are estimated to assess the robustness of the empirical relationships. The Hausman test does not reject the random effects specification, suggesting that the random effects estimator is statistically acceptable. Nevertheless, fixed effects results are also reported to account for unobserved country- and time-specific heterogeneity. The empirical findings show that GDP per capita has a negative and statistically significant effect on undernourishment across both model specifications, indicating that higher income levels are associated with improved food access and better nutritional outcomes. Inflation has a positive and statistically significant effect, suggesting that rising prices may weaken household purchasing power and increase undernourishment. Agricultural value added is positive but statistically insignificant, implying that agricultural expansion alone may not be sufficient to reduce undernourishment unless supported by improvements in productivity, distribution, food access, and institutional efficiency. Urbanization and trade openness generally show negative associations with undernourishment, although their statistical significance varies across model specifications. From a sustainability perspective, reducing undernourishment requires more than aggregate income growth or agricultural expansion. Policies should strengthen resilient food systems, improve agricultural productivity, enhance social protection mechanisms, stabilize food prices, and ensure equitable access to affordable and nutritious food. This study contributes to the literature by providing recent panel-based evidence on the joint role of income, agricultural structure, inflation, urbanization, and trade openness in explaining undernourishment, and by offering policy-relevant insights for designing sustainable and inclusive food systems in developing countries.