Is smelling your food making you fat? Smell and metabolism may be more closely connected than we realize, a new study suggests.
Researchers at the University of California, Berkeley, temporarily eliminated the sense of smell in adult mice and found that obese smell-deficient mice shed serious weight, slimming down to a sleek physique even while eating a high-fat diet. Meanwhile, mice who retained their sense of smell ate the very same amount of fatty food (and moved around the same amount) as the smell-deficient mice and packed on the weight, ballooning to twice their previous weight, the researchers say.
A third group of mice with a super sharp sense of smell — super smellers — were also fed the same amount of fatty food. Guess what happened to them? Yep. They bulked up even more on the high-fat diet than the mice with normal senses of smell.
The research suggest that our ability to smell food goes beyond just helping us find and assess it. It may play an active role in metabolism, affecting the way our body contends with calories – rewiring our brain to signal whether to burn fat or store it.
One theory about what’s going on here is that because we are less sensitive to smell after we have eaten than when we are hungry, removing the sense of smell tricks the body into thinking it has already eaten and doesn’t need the calories it is taking in, making it free to burn them.
So might the link between smell and weight hold true for humans, as well as mice? “It has a good chance,” Andrew Dillin, the molecular and cell biologist who led the study, tells Healthy Eats. “We know that smell is linked to hunger and satiety in humans. When hungry, our sense of smell increases and after eating our sense of smell decreases…so I think it will be conserved.”
Alas, simply holding your nose when eating won’t help you shed pounds. Working with the mice, the scientists used gene therapy to temporarily eliminate the neurons that sense odorants. (Don’t worry; the olfactory neurons grew back in about three weeks and the mice could go back to their normal smell-sensing selves.)
However, “It will be interesting to ask if obese people can be stratified based on their ability to smell. Perhaps there is a population of obese humans that are super smellers,” Dillin says. “Sensory perception, or how we perceive our calories, could have a profound impact upon health in some individuals.”
And that’s nothing to sniff at.
Amy Reiter is a writer and editor based in New York. Her work has appeared in publications including The Los Angeles Times, The New York Times, The Washington Post, The Daily Beast, Glamour and Marie Claire, as well as Salon, where she was a longtime editor and senior writer. In addition to contributing to Healthy Eats, she blogs for Food Network’s FN Dish.