Insulin Resistance Is Associated with Reduced Food Odor Sensitivity across a Wide Range of Body Weights

Abstract

The worldwide obesity epidemic is a major health problem driven by the modern food environment. Recently, it has been shown that smell perception plays a key role in eating behavior and is altered in obesity. However, the underlying mechanisms of this phenomenon are not well understood yet. Since the olfactory system is closely linked to the endocrine system, we hypothesized that hormonal shifts in obesity might explain this relationship. In a within-subject, repeated-measures design, we investigated sensitivity to a food and a non-food odor in the hungry and sated state in 75 young healthy (26 normal weight, 25 overweight, and 24 obese) participants (37 women). To determine metabolic health status and hormonal reactivity in response to food intake, we assessed pre- and postprandial levels of insulin, leptin, glucose, and ghrelin. Odor sensitivity did not directly depend on body weight status/body mass index (BMI) or hunger state. However, we could establish a strong negative mediating effect of insulin resistance on the relationship between BMI/waist-hip ratio and olfactory sensitivity for the food odor. These findings indicate an impact of metabolic health status on sensitivity to food odors. Our results contribute to a better understanding of the mechanisms behind altered smell perception in obesity.

Reduced Olfactory Bulb Volume in Obesity and Its Relation to Metabolic Health Status

“…As to the first point, we think that our very young and healthy obese sample may be the reason for the preserved olfactory ability. As discussed by the authors of this paper it is plausible that individuals with obesity that are metabolically healthy may have normal olfactory function (Poessel et al, 2020). This point of view is in line with another finding that especially people that are morbidly obese when compared to moderately obese are affected from limitations in olfactory function (Richardson et al, 2004).…”

“…The mechanisms behind these alterations remain unclear, however, it has been suggested that decreased olfactory function may be caused by hormonal and metabolic changes that are associated with obesity (Peng et al, 2019). This is supported by a recent finding of our working group, where we could show that high insulin resistance has a negative effect on food odor sensitivity in obesity (Poessel et al, 2020). Moreover, these hormonal changes might lead to altered function of the olfactory bulbs (Lacroix et al, 2015).…”

“…For instance, leptin, which is often increased in obesity while their brain is insensitive to this hormone, has an inhibitory role on olfactory function in mice (Getchell et al, 2006). In line with this reasoning, it is interesting that we could replicate our results from Poessel et al (2020) in this sample. We find a strong mediating effect of insulin resistance as assessed by HOMA-IR score on the relationship between BMI and olfactory function as assessed by TDI score.…”

Increased Brain Reward Responsivity to Food‐Related Odors in Obesity

“…Moreover, the brain activation of the group × odor type interaction was not affected when including odor threshold as a covariate, implying that the impaired olfactory function was not the inherent cause for this effect. A recent study suggested a link between insulin resistance and reduced olfactory sensitivity (37). Whether obesity‐related alteration of olfaction is also generalized to all types of food odors remains to be elucidated.…”

Does Each Menstrual Cycle Elicit a Distinct Effect on Olfactory and Gustatory Perception?

“…Many factors have demonstrated a modifying effect on the perception of taste and odor stimuli. Some of the important determinants include sex [ 7 ], age [ 4 , 8 ], genetic factors [ 9 ], ethnicity [ 10 ], obesity [ 11 ], metabolic syndrome [ 12 ], diabetes [ 13 ], insulin resistance [ 14 ], hunger [ 15 ], certain medications [ 16 , 17 ], and possibly even the oral microbiota composition [ 5 ] and hormonal fluctuations, especially during pregnancy [ 18 ] and throughout the menstrual cycle [ 19 ]. Gender differences are reported in almost every sensory system in humans [ 7 ].…”