Overall, UPF production is analyzed regarding its impacts on the environment, biodiversity, animal wellbeing, and cultural and socio-economic dimensions. Our main conclusion is that UPFs are associated with intensive agriculture/livestock and threaten all dimensions of food system sustainability due to the combination of low-cost ingredients at purchase and increased consumption worldwide. However, plant-based UPFs do not produce the highest greenhouse gas emissions (GHGEs) compared to conventional meat and dairy products. In addition, only reducing energy-dense UPF consumption (associated with excess calorie intakes), without substitution, might substantially reduce GHGEs. Therefore, significant improvement in food system sustainability requires urgently encouraging limiting UPF consumption to the benefit of mildly processed foods, preferably seasonal, organic and local products, a recommendation that we formalized in the concept of the 3V-based diet for Végétal (Plant), Vrai (Real foods), Varié (Varied, preferably organic, local and seasonal - when possible).