One of the more interesting physiological changes that is elicited by scent is hunger/satiety.
Hunger is a biochemical event that is controlled by an area of the brain called the ventromedial nuclei of hypothalamus. When this specific region of the hypothalamus is stimulated, hunger results. When a different area of the hypothalamus, the lateral nucleus, is stimulated, appetite suppression occurs. It's really that simple.
What might be a surprise to most non-biochemists, however, is the undisputable fact that the fastest and most direct method of hypothalamic stimulation is actually accomplished through smell. To the point, there are olfactory stimuli (scents) that can create hunger and others that can suppress appetite.