A high-fat diet could cause you to lose your sense of smell, according to a study from the Florida State University. Researchers induced obesity in mice by feeding them high-fat diets for six months. As a result, the mice lost significant function in their olfactory nerves. They also learned reward-reinforced behaviors more slowly, had deficits in reversal learning, demonstrated behavioral inflexibility, and showed reduced ability to discriminate between smells. When removed from the high-fat diets, the mice regained their normal body weight, but the olfactory dysfunction remained. In fact, the mice were left with only 50% of the neurons that operate to encode odor signals. The researchers conclude that excessive calorie intake from fat leads to long-term structural and functional changes in the olfactory system, which gives animals and humans a sense of smell, as well as significant changes in reward-driven behaviors.
In Perspective: This is the first study to show a link between excess body fat and reduced ability to smell and opens up a whole new world of possibilities on how obesity affects bodily functions not previously considered when studying the impact of weight gain on health.
Thiebaud N, Johnson M, Butler J, et al: Hyperlipidemic diet causes loss of olfactory sensory neurons, reduces olfactory discrimination, and disrupts odor-reversal learning. Journal of Neuroscience 2014;34:6970-6984.