The vast heterogeneity in dietary practices and demographic structures across China has led to pronounced regional disparities in food demand and environmental impacts. Yet, most existing assessments remain at the national level, overlooking regional diversity and differences in nutritional intake. This study integrates provincial dietary preferences, age–gender–residence–specific energy requirements, and environmental constraints on cropland, blue water, and greenhouse gas (GHG) emissions under the shared socio-economic pathways (SSPs). By 2050, national food demand is projected at 403–510 Mt, requiring 53–66 Mha of cropland, 128–148 km3 of blue water, and 544–790 MtCO2e of GHG emissions. Diets with carbohydrate-derived energy exceeding 55% exhibit lower environmental pressures and greater alignment with sustainability goals than the Chinese Dietary Guidelines. The findings offer critical insights into regional diet-environment linkages and support the development of food management strategies tailored to diverse regional conditions.