Research Closeup: Smell and Obesity

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You’re probably familiar with how your sense of smell affects hunger, like when  a whiff of freshly baked bread  triggers a sudden desire for a sandwich.

New research suggests smell might influence not only our appetites, but also how our bodies process food.

By regulating the olfactory system, we can control the brain’s response to food.

Celine Riera, PhD, is assistant professor in the Center for Neural Science and Medicine at Cedars-Sinai. Her research focuses on mapping the brain circuits to understand pathways that affect obesity. In a recent study, Riera uncovered a connection between olfactory neurons, which control smell, and metabolism, the body’s process of converting food into energy.

We spoke with Riera about her work and her hopes for how it might someday help treat obesity.

We’re starting to appreciate now that one of the main causes of obesity—and the reason it is so difficult to lose weight or keep it off—is that hunger and appetite are not something people can control. Click To Tweet

Why are hunger and smell interconnected?

Celine Riera: We’ve found that mice stay leaner when their olfactory neurons, their “smell receptors,” are turned off—even when they eat the same diet as mice whose neurons are normal. These mice without a sense of smell burn more calories, stay more active, breathe more oxygen, and have a higher metabolism.

Olfaction, the act of smelling, can influence the hypothalamus, an area of the brain which controls hunger: Mice who can’t smell appear to perceive food differently.

What else have you learned from this research?

CR: We’ve discovered that the neurons inside our nose send information to the brain and govern how much food we need, whether to look for food, and how to process the food we eat.

The brain is like the master conductor and the body is the orchestra: The brain sends hunger information to every other part of the body. So by regulating the olfactory system, we can control the brain’s response to food.


Read: Explaining the Link Between Prostate Cancer and Obesity


How could this help patients in the future?

CR: This animal research may give us the opportunity to better understand the causes of obesity in humans.

We’re starting to appreciate now that one of the main causes of obesity—and the reason it is so difficult to lose weight or keep it off—is that hunger and appetite are not something people can control.

Hunger happens in the nervous system, at the neuron level, and it is extremely important to understand this aspect of the disease. If we can manipulate hunger response through smell, we could potentially regulate the way the body processes food.

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