The role of ambient odors in the regulation of food intake in humans

The sense of smell plays an appetizing, priming role in eating behaviour: conscious exposure to odors can specifically steer appetite towards similar foods, while unattended odors may guide food choice. However, the exact nature of odor influences on subsequent food intake is not yet clear. The aim of the current study was to investigate the effects of low-intensity ambient odor exposure on appetite, saliva production and food intake. 32 normal-weight female participants attended five separate test sessions, in which they were exposed for ~30min to ambient odors in a barely detectable intensity: beef (high energy, savory), chocolate (high-energy, sweet), melon (low-energy, sweet), cucumber (low-energy, savory), and no odor (control). In each session, they rated appetite for products (un)related to the odors, and saliva production and ad libitum food intake (chocolate rice; sweet, high energy) was measured. Mixed model analyses show that specific appetite was not influenced by odor exposure (p=.639). However, ad libitum intake increased by 22% after exposure to odors similar in energy-density (chocolate, beef; both p=.01), compared to the control condition. Similarly, saliva production was higher when exposed to high-energy odors compared to control (chocolate, p=.002, beef, p=.03 ). Taken together, these and other results show that odors can specifically affect food intake regulation, but these effects may depend on the concentration or awareness of it.