The delicious smell of sweets emanating from the front door may entice you into a corner bakery. Knowing that individuals make judgments based on smell, large brands like Cinnabon and Panera Bread have pumped baked goods scents into their restaurants, resulting in huge sales jumps.
However, a new study suggests that the meal you ate prior to walking past the bakery may have an effect on your likelihood of going in for a sweet treat—and not just because you’re full.
According to researchers at Northwestern University, people become less sensitive to food scents based on the meal they just had. Therefore, if you snacked on baked goods from a coworker before your walk, you may be less likely to stop into that scented bakery.
The researchers discovered that people who had just consumed cinnamon buns or pizza were less likely to perceive “meal-matched” scents, but not unmatched scents. The findings were then validated by brain scans that revealed similar changes in brain activity in areas of the brain that process scents.
These studies demonstrate that, just as smell influences what we eat, food influences our sense of smell.
According to senior and corresponding study author Thorsten Kahnt, an assistant professor of neurology, psychiatry, and behavioural sciences at Northwestern University Feinberg School of Medicine, feedback between food intake and the olfactory system may have evolutionary benefits.
While the hunter-gatherer adaptation does not manifest itself in daily decision-making, Kahnt believes the relationship between our nose, what we want, and what we can detect with our nose may still be critical. If the nose, for example, is not functioning properly, the feedback loop may be disturbed, resulting in issues with compulsive eating and obesity. There may even be connections to insomnia, another aspect of the olfactory system being studied by the Kahnt lab.
To perform the study, the researchers devised a unique task in which participants smelled a blend of food and a non-food odor (either “pizza and pine” or “cinnamon bun and cedar”—odors that “pair well” but are distinct from one another). Each mixture contained a different ratio of food and non-food odors, ranging from pure food to pure non-food. Following the presentation of a mixture, participants were asked whether the food or non-food odour was more dominant.
The task was repeated twice within an MRI scanner: once when participants were hungry and once after they ate a meal that matched one of the two scents.
The researchers then calculated the amount of food aroma required in each session for the individual to perceive it as dominant. The researchers discovered that when individuals were hungry, they need a lower proportion of food scent in a mixture to perceive it as dominant—for example, a hungry person may require a 50 percent cinnamon bun-to-cedar mixture, but 80 percent when they were full of cinnamon buns.
The team offered additional evidence for the concept via brain imaging. Brain scans from the MRI revealed a corresponding shift in the area of the brain responsible for olfactory processing following a meal. The brain’s response to a meal-matched odor was less “food-like” than responses to non-meal matched odor.
“After the meal, the olfactory cortex didn’t represent meal-matched food odors as much as food anymore, so the adaptation seems to be happening relatively early on in processing,” Kahnt said.
“We’re following up on how that information is changed and how the altered information is used by the rest of the brain to make decisions about food intake.”
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