By Nora Siblani MS LD
Nutrition Consultant & Clinical Dietitian
F B: Nora’s Nutrition and Health
Can obesity lead to loss of smell?! High fat meals may intimidate your sense of smell. Could this be another undesirable outcome of bad eating habits and obesity? Your favorite fatty meals may alter your ability of smelling your morning cup of coffee, fresh loaf of bread at the bakery, cut grass in a garden, aroma while sipping on a glass of wine, roses from your partner or his/her eau de parfum…
Here is a brief description of how your sense of smell works. Smelling is a chemical sense functioned by the olfactory system. The olfactory sensory neurons are found inside the nose in a specialized olfactory mucosa of the nasal cavity. The cells that make up the neurons are directly connected to the brain. The receptors of the olfactory neurons are stimulated by any chemical compound that triggers an odor. This stimulation leads to the transmission of a message to the brain that will result in the classification and identification of the smell. The smelling sensation helps you better taste the food you are eating. If the olfactory system is not functioning as it would normally do, then the perception of food flavors might be mistaken. For instance, a stuffy nose might prevent you from enjoying a flavorful meal. This makes smelling and the odor of food important factors that may influence food choices and intake.
There is no doubt that obesity is a serious and growing epidemic. According to the WHO, a minimum of 2.8 million people are dying each year due to overweight and obesity. Obesity is mainly caused by an imbalance of calories taken and calories expended. The significant and detrimental effects of obesity have been considerably demonstrated in many research and studies whether physical or psychological, such as cardiovascular problems, diabetes, high blood pressure, depression or low self esteem. Very few studies have investigated the consequences of obesity on the sensory systems, especially on the olfactory system.
A recent study by the post-doctoral researcher, Nicolas Thiebaud, and colleagues investigated the impact of obesity on the olfactory system. The study was conducted at the Florida State University in the lab of Biological Science Professor Debra Ann Fadool, and is published in the Journal of Neuroscience. For over a six-month period, the neuroscientists and researchers observed the impact of high fat meals on smelling in mice. The mice were fed high fat meals to cause long-term obesity. At the same time, the mice were taught to associate between a particular odor and reward (as water). A control group, which included mice that were not exposed to high fat meals, was also included in the study as a benchmark for evaluating results. When compared to the control group, the diet-induced obese mice were slower at learning the association. The results of the study showed that obese mice with high fat diets exhibit poor or reduced olfactory discrimination, meaning that they were not able to differentiate odors. This impairment is justified by the loss of 50% of the neurons that encode odor signals. When the mice were removed from high fat diets, they still had lower olfactory abilities, even after they lost weight to reach normal levels. This study shows that there might be a link between obesity due high fat diets with a decreased ability to smell.
This study has been done on mice and not on humans; yet, it opens doors to many other investigations. Obesity resulted from high sugar meals may cause different effects than high fat meals. Further studies in this area are needed, as they may be a key factor in reducing obesity and related health risks and complications. This unfavorable and damaging outcome gives another rational reason to avoid high fat meals and to reduce risk of obesity.
If your sense of smell is important to you, watch out from high fat diets!