It has long been understood that smell influences our sense of taste, but new research has now provided evidence that it may also impact our ability to maintain a healthy weight. In an animal study recently conducted at University of California, Berkeley, researchers found evidence that our olfactory system is not only associated with our enjoyment of food, but also how we metabolize it.
In a study published in the July 2017 issue of Cell Metabolism, researchers separated mice into control and experimental groups, then used gene therapy to temporarily inhibit the sense of smell of those in the experimental group. All mice were put on a calorically-dense and high-fat diet and monitored over a three-week period for changes in body composition and various biological mechanisms that influence weight. What researchers found was immediate and unpredicted responses by several different body systems. The newly olfactory-deficient mice experienced an increase in sympathetic nervous system activity, the component of the autonomic nervous system that previous research has shown is associated with fat burning. The composition of their fat cells also experienced a significant transformation. Beige adipose cells, those subcutaneous cells that tend to stockpile energy around the midsection, began converting to brown cells, which promote increased fat metabolism. Furthermore, white adipose cells, which are known to cluster around internal organs and promote poor health outcomes, such as glucose intolerance, began shrinking in size. Even more shocking, glucose tolerance in the experimental group actually improved despite the high-calorie and high-fat diet. To conclude the trial, the researchers collaborated with German colleagues to temporarily enhance the sensitivity of a third set of mice and found that those with super-sniffers gained even more weight than the control group. There was one noted negative side effect displayed by the experimental group: an increased secretion of noradrenaline, a stress hormone that (when levels are chronically raised) is associated with increased risk for cardiovascular disease and adverse cardiovascular events.
In a world where science is constantly looking for the fountain of abs, should we expect year-long waiting lists to see your ear, nose, and throat specialists for smell-blocking procedures? First, although animal studies provide a framework for us to further understand biological mechanisms of action, humans are a unique species and things don’t always work the same in human trials as they do in examination of our furry little friends. Second, the methods currently used to temporarily impede the proper function of the olfactory system are pretty cringeworthy. The most effective current method involves spraying live bacterium Corynebacterium diphtheria into one’s nose, which may or may not result in contracting the diphtheria infection and temporarily killing olfactory neurons until stem cells regenerate them. In other words, no, don’t expect this to become a common procedure for humans anytime in the near future, but it is a first step in understanding the neural circuitry involved in metabolism.
It’s an exciting time to be involved in the study of fat. The next wave of weight management research may not be novel dietary regimens or metabolism-boosting thermogenics, but how our nose and brain work together to regulate how our body alters lipid composition and metabolism.
Dr. Damian Rodriguez is the health and exercise scientist for doTERRA International, LLC. He holds a doctorate in health science, a master’s degree in exercise physiology, and countless professional certifications. He has spent most of his life researching nutrition, exercise, and the lifestyle behaviors associated with optimal health. Along with his passion for health, as someone who lives with Asperger’s Syndrome, he is also involved in bringing awareness to autism spectrum disorders. There are varying opinions about many health and fitness topics. His opinions are his own and not necessarily that of doTERRA International, LLC. Consult your healthcare provider before making any changes to diet and exercise.