Managing food intake is critical for survival. Either too little food or too much food can seriously impair well-being. As most animals, including humans, regulate their energy needs by consuming food in distinct bouts or meals, it is important to understand the mechanisms controlling meal-taking behavior. Appetite, defined as the desire to consume foods, promotes meal intake, while satiety, defined as a feeling of fullness resulting from having consumed sufficient food, typically leads to the cessation of a meal. As described in this entry, appetite and satiety are governed by both internal physiological signals and external environmental cues.