Appetite is a powerful yet often misunderstood driver of eating behavior. While hunger reflects the body’s physiological need for energy, appetite is shaped by desire, anticipation, memory, and emotion. A single sensory cue—the smell of fresh bread, the sight of a cold drink, or the sound of food cooking—can instantly trigger craving, salivation, and motivation to eat, even in the absence of true hunger. At the same time, appetite can disappear during stress, illness, or emotional strain, despite clear physiological need. Understanding appetite therefore requires looking beyond calories and nutrients to the complex interaction between sensory input, brain processing, and lived experience. Smell plays a particularly important role in this system. Unlike other senses, olfaction has direct access to brain regions involved in memory, emotion, and reward, allowing food-related odors to evoke powerful anticipatory responses. These responses prepare the body for eating and strongly influence food choice, portion size, and enjoyment. When smell is reduced, distorted, or lost, appetite regulation can change in profound and highly individual ways—sometimes leading to loss of interest in food, and other times to overeating in search of satisfaction. In this chapter, we examine the distinction between hunger and appetite and describe how appetite is regulated by sensory cues, hormones, neurotransmitters, and brain networks involved in motivation and reward. We explore the central role of smell in anticipation and consumption, the formation of conditioned food responses, and how stress and emotion modulate appetite. Finally, we discuss how appetite may be disrupted by smell loss and outline principles for restoring a satisfying relationship with food through adaptation, learning, and multisensory engagement.