Smelling Food "Fires" the Brain Differently than Actually Eating Food

Smelling food activates different brain areas than consuming it, according to a Yale University study published in Neuron that shows definitively what researchers have long suspected.

“We believe that these findings add to our understanding of chemosensation and food reward and will have important implications in addressing the obesity epidemic,” said lead author Dana Small, assistant professor of psychiatry and associate fellow of the John B. Pierce Laboratory.

Small and her colleagues are interested in understanding how sensory processing interacts with behavioral choices such as decisions to eat or stop eating in healthy individuals and in people with eating disorders. Theorists have postulated that overeating results from a heightened sensitivity to food reward. Others, Small said, have argued that people overeat because they experience less pleasure from eating and eat to boost a sluggish reward system. She said these two seemingly contradictory theories may be reconciled if food reward is considered as multifaceted.

“For example, it could be that some people are more sensitive, and less able to resist, food cues, such as an aroma of freshly baked bread, and that these same people also experience less pleasure when actually eating the food,” Small said.

In this study Small and her co-authors describe the circuits that code the properties of these two facets of food reward. The study was based on two functional magnetic resonance imaging (fMRI) studies in which subjects sniffed food aromas and drank the drinks associated with the aromas while undergoing scanning. The food odors were pineapple and peach in the first experiment and pineapple and chocolate in the second experiment. The drinks were pineapple, peach, and a chocolate milkshake.

What the team observed is that different areas of the brain respond to the aroma of chocolate, peach, or pineapple compared to the ingestion of those foods.

Small said the group currently is studying responses to food aromas and food ingestion as a function of weight and eating style.

The research was funded by grants from Unilever Research and the National Institutes of Health.

Co-authors include Maria Veldhuizen, Jennifer Felsted, Y. Erica Mak, and Francis McGlone.

Neuron: March 14, 2008

The work above was funded, fully or in part, by the Yale Clinical and Translational Science Award (CTSA) grant from the National Center for Research Resources at the National Institutes of Health.