Producing a definition of healthful eating that expresses adequately the richness and the complexity of the eating experience is challenging. Still, the effort is crucial if one wants to promote behavioural change in the population, as well as a transformation of interventional practices, programs, and policies, and even the agri-food system. We explain that the biological, social, and environmental dimensions of healthful eating, along with the interactions among them, must be addressed. Once these dimensions are considered as a whole, the definition of healthful eating allows the identification of a wide range of strategic interventions to implement such eating. We suggest a continuum of eating quality that could be used to identify, in general, the food habits of persons or groups.