Nutrition (Latin nutrire: nourish) is the set of processes by which a living being transforms food to ensure its functioning. Nutrition is also a multidisciplinary science, with two main themes. On the one hand, the physiology of nutrition deals with how the body processes food processing, that is, metabolic processes. This involves the study of the role of macronutrients and micronutrients in cellular biochemical mechanisms, and the effects on tissues of an imbalance between the energy absorbed and the energy expended by the body. On the other hand, the psychology of nutrition analyzes the eating behavior of the individual or group. It focuses on issues such as "why are we eating? Or "how do we choose our food? ". In humans, these issues are related to environmental factors such as the built environment, the media and health policies, as well as its particularities such as income or culture.