Much scientific literature proposes reduction of animal-source foods to reduce environmental impacts of the food system. However, these dietary solutions differ regarding level and type of animal-source foods. We review this literature and our results show that these differences relate to differences in employed methodological approaches. Approaches that consider systemic consequences throughout the food system propose to limit livestock to low-opportunity-cost feed, where feed availability drives level and type of animal-source foods, resulting in poultry and pork being reduced most. Approaches with fixed impacts propose to reduce animal-source foods depending on current impact intensities, suggesting largest reductions for beef. By linking differences in dietary solutions to methodological approaches, our results contribute to informed choices of researchers, policy makers, and consumers.