Socioeconomic status, gender, and ethnicity are all known to play a role in the risk of developing obesity. African Americans and Latinos are more likely to be obese than Caucasians; those achieving a higher level of education are less likely to be obese; adults from lower income households are more likely to be obese; and the prevalence of severe obesity is higher in women than men. According to a study from the University of Otago in New Zealand, the more sensitive an individual’s sense of smell, the less likely he or she is to develop obesity.
Your Nose Receptors Detect 10,000 Different Smells
Although commonly thought of as two separate senses in the human body, the senses of smell and taste are closely intertwined. Both smell and taste involve chemoreceptors, sensory cells that react to the chemical environment, and both activate during the course of eating. If you think about the last time you tried to enjoy a meal while suffering a blocked nose, apart from not being able to breathe properly (as breathing is also a vital part of appreciating a meal), you probably found the flavor wasn’t quite there.
What we think of as the taste of food is governed by the interactions between the chemical molecules of the food flavors, the olfactory receptors of the nasal cavity, and the taste buds of the mouth. While the human tongue can distinguish five primary tastes (sweet, sour, salty, bitter, and umami), the human nose has around 350 types of olfactory receptors that allow us to detect about 10,000 different smells. Although the exact contribution of the sense of smell to our perception of flavor is controversial, it is widely accepted that smell makes up a dominant proportion of the pleasurable experience that we call “tasting food.”
Decreased Smell Sensitivity Linked to an Increase in Body Weight
The research paper released by the University of Otago found that our ability to smell the chemosensory world can play a role in our food choices and eating behaviors. Studies indicated a pattern of decreasing smell sensitivity associated with an increase in body weight. Although the ability to identify different aromas did not differ between different weight groups, the ability to actually detect these odors was found to be superior in healthy-weight populations when compared to obesity groups. The researchers hypothesized that a poorer sense of smell may result in individuals making more unhealthy food choices as they are more attracted to tastier, more flavorful foods (think candied bacon, pizza with the lot, and ice-cream sundaes) as an over-stimulation of the taste chemoreceptors which compensate for the lack of sense of smell. Not only does constant indulgence in high-salt, high-sugar content foods cause obesity, but the metabolic changes in the body associated with obesity further affect the ability to smell, leading to increased difficulty in making healthy food choices.
Can Obesity Surgery Improve the Ability to Smell?
It is quite common for changes in appetite and the sense of taste to be reported after undergoing obesity surgeries. Changes to smell perception have also been reported though less often; however, this is thought to be more related to the lower amount of attention given to olfactory functions in these studies.
Two of the most common bariatric surgeries – gastric bypass surgery and sleeve gastrectomy – were investigated to determine whether these procedures had any affect in improving the ability to smell in previously obese patients. Sleeve gastrectomy (reducing stomach capacity by surgically removing part of the stomach, thereby reducing appetite) in particular was found to have the potential to improve olfactory function across all three measures of smell – odor discrimination, identification, and sensitivity. It is thought that in the course of bariatric surgery, disruptions are caused to the neural and hormonal networks involved in detecting stomach fullness, the feeling of hunger, and the sense of smell. In other words, the gut-to-brain pathway is reconfigured and stimulated, sensitizing the olfactory processes and improving the ability to smell. Considering this, in addition to reducing appetite by surgically decreasing stomach size, weight loss after sleeve gastrectomy could also be a product of a heightened sense of smell and the effect this has on food choices and eating behavior.
With increasing insight into obesity as a disease, the medical profession is now realizing that while some factors are voluntary, such as certain lifestyle choices, other contributors to the development of obesity may be more out of our control. Understanding the association between an individual’s perception of smell and their risk of obesity is just one step closer to smelling like teen spirit.
Adult obesity rates rise in 6 states, exceed 35% in 7. https://www.ama-assn.org/delivering-care/public-health/adult-obesity-rates-rise-6-states-exceed-35-7
Taste and smell. https://courses.lumenlearning.com/boundless-biology/chapter/taste-and-smell/
Just how much of what we taste derives from the sense of smell? https://flavourjournal.biomedcentral.com/articles/10.1186/s13411-015-0040-2
The link between poor sense of smell and diseases from obesity to Alzheimers. https://reachmd.com/news/the-link-between-poor-sense-of-smell-and-diseases-from-obesity-to-alzheimers/1623095/
Study finds link between obesity and sense of smell. https://www.medicalnewstoday.com/articles/323989.php
Systematic review of olfactory shifts related to obesity. https://onlinelibrary.wiley.com/doi/epdf/10.1111/obr.12800?referrer_access_token=Yo-rS57IRxWGAUFe5UYaEIta6bR2k8jH0KrdpFOxC64f49oGgHriBYSHneBpb6p-yg4_xVHc_UOmTN9uk421XH13yWNqkJdkATE5EUef_SWIe614OZ73P6QxBHV1SV4TAjS7QVQQwEruyLnu0HY1bA%3D%3D